How to Calculate Peptide Dosing: Math Guide with Examples and Calculator

# How to Calculate Peptide Dosing: Math Guide with Examples and Calculator

> For research purposes only. All dosing information in this guide is for laboratory research use only. This is not medical dosing guidance.

Peptide dosing calculations are a frequent source of errors — and errors in concentration mean your experiments are based on doses you think you're delivering but aren't. This guide walks through every step of the math systematically, with worked examples, common mistakes, and a framework that works for any peptide in any unit system.

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Why Peptide Dosing Math Goes Wrong

Before getting into formulas, it's worth understanding the common failure points:

1. Unit confusion: µg, mg, nmol, pmol — mixing these is the most common error

2. Ignoring water content: Lyophilized peptides contain 5–15% water by weight; if you weigh 5mg of powder, you may have only 4.25–4.75mg of actual peptide

3. Ignoring counter-ion weight: TFA or acetate counter-ions add weight; a "5mg vial" may contain 3.8–4.5mg of net peptide

4. Incorrect volume math: Adding 1mL to a vial doesn't mean you have exactly 1mL of solution — the powder has some volume (minor but relevant at high concentrations)

5. Reconstitution errors: Adding the wrong volume of reconstitution vehicle entirely

6. Calculation chain errors: Making a small error early in a multi-step dilution that compounds through subsequent calculations

This guide addresses all of these.

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Unit Reference: Master This Before Calculating

Weight Units

Volume Units

Concentration Units

Key conversion: 1 mg/mL = 1,000 µg/mL = 1 µg/µL

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Step 1: Know Your Starting Material

Before any calculation, establish the true amount of peptide in your vial.

Simple Case: No Net Peptide Content Listed

If your COA shows "5mg" and no net peptide content information:

• •Use 5mg as your starting value
• •Acknowledge this may be slightly less actual peptide (5–15% water + counter-ion weight)
• •For exploratory research, this is often acceptable

Better Case: Net Peptide Content Listed

Some COAs list "Peptide Content: 85%" or "Net Peptide Content: 4.25mg per 5mg vial"

If peptide content = 85%:

• •Actual peptide in "5mg vial" = 5mg × 0.85 = 4.25mg
• •Use 4.25mg in all subsequent calculations, not 5mg

Formula: Actual peptide = Labeled weight × (Peptide content% / 100)

Why This Matters: Example

You order 5mg BPC-157. COA shows 83% net peptide content.

• •Actual peptide = 5mg × 0.83 = 4.15mg
• •If you ignore this and assume 5mg, your concentration is off by 17%
• •Every dose calculation downstream is wrong by 17%

For protocols calling for specific concentration windows, 17% error can move you below or above the effective range.

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Step 2: Calculate Reconstitution Volume

The Basic Reconstitution Formula

Target concentration (mg/mL) = Peptide weight (mg) / Reconstitution volume (mL)

Or rearranged: Reconstitution volume (mL) = Peptide weight (mg) / Target concentration (mg/mL)

Worked Example 1: Standard Reconstitution

Scenario: 5mg BPC-157 vial. Target concentration: 5mg/mL.

Volume = 5mg / 5mg/mL = 1.0 mL

Add 1.0mL bacteriostatic water → 5mg/mL solution

Worked Example 2: Lower Concentration Stock

Scenario: 5mg BPC-157. Want 2.5mg/mL stock (for easier dilution in experiments).

Volume = 5mg / 2.5mg/mL = 2.0 mL

Add 2.0mL → 2.5mg/mL solution

Worked Example 3: With Net Peptide Content Correction

Scenario: 5mg vial, 83% net peptide content. Target 5mg/mL.

Actual peptide = 5mg × 0.83 = 4.15mg

Volume = 4.15mg / 5mg/mL = 0.83 mL

Add 0.83mL → 5mg/mL solution

(Note: most researchers simplify to ~0.8mL or 0.85mL in practice)

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Step 3: Convert Between mg/mL and µg/mL

This is a common source of confusion.

1 mg/mL = 1,000 µg/mL = 1,000,000 ng/mL

Example Conversions

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Step 4: Calculate Working Dilutions

Most experiments use a working concentration that is different (lower) than your stock concentration. You need a dilution.

The Dilution Formula: C₁V₁ = C₂V₂

C₁ = starting concentration

V₁ = volume of stock to use

C₂ = desired final concentration

V₂ = desired final volume

Rearranged to find V₁: V₁ = (C₂ × V₂) / C₁

Worked Example 4: Simple Dilution

Scenario: Stock is 5mg/mL. Need 0.5mg/mL working solution. Final volume = 10mL.

V₁ = (0.5 mg/mL × 10 mL) / 5 mg/mL = 1.0 mL stock

Mix 1.0mL stock + 9.0mL diluent = 10mL at 0.5mg/mL

Check: 1.0mL × 5mg/mL = 5mg total. 5mg / 10mL = 0.5mg/mL ✓

Worked Example 5: Working in µg/mL

Scenario: Stock is 5mg/mL (= 5,000µg/mL). Need 100µg/mL working solution. Final volume = 5mL.

V₁ = (100 µg/mL × 5 mL) / 5,000 µg/mL = 0.1 mL = 100µL stock

Mix 100µL stock + 4.9mL diluent = 5mL at 100µg/mL

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Step 5: Convert to Molar Concentration

Some experiments require molar concentration (nanomolar, micromolar) rather than mass-based concentration. This requires knowing the molecular weight (MW) of the peptide.

The Molar Conversion Formula

Molarity (M) = (mass in grams) / (MW in g/mol × volume in liters)

More practically:

µM (micromolar) = [µg/mL] × [1,000 / MW in Da]

Or equivalently:

µM = [mg/mL] × [1,000,000 / MW in Da]

Worked Example 6: Converting BPC-157 to µM

BPC-157 molecular weight: ~1,419.5 Da (= 1,419.5 g/mol)

Stock: 5mg/mL

µM = 5 mg/mL × (1,000,000 / 1,419.5)

µM = 5 × 704.5

µM = 3,523 µM ≈ 3.52 mM

Working solution at 100µg/mL:

µM = 0.1 mg/mL × (1,000,000 / 1,419.5)

µM = 0.1 × 704.5

µM = 70.5 µM

Worked Example 7: Converting Semaglutide to nM

Semaglutide molecular weight: ~4,113.6 Da

Working concentration: 1µg/mL (= 0.001 mg/mL)

µM = 0.001 mg/mL × (1,000,000 / 4,113.6)

µM = 0.001 × 243.1

µM = 0.243 µM = 243 nM

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Step 6: Body Weight-Based Dosing (In Vivo Research)

For rodent in vivo studies, doses are typically expressed per body weight: µg/kg or mg/kg.

The In Vivo Dosing Formula

Volume to inject (mL) = [Dose (µg/kg) × Body weight (kg)] / Concentration (µg/mL)

Worked Example 8: BPC-157 Rodent Dosing

Scenario: Dosing BPC-157 at 10µg/kg in a 300g rat. Stock concentration: 500µg/mL.

Body weight in kg = 300g / 1,000 = 0.3 kg

Total dose = 10µg/kg × 0.3kg = 3µg total

Volume to inject = 3µg / 500µg/mL = 0.006mL = 6µL

Note: 6µL is a very small volume for injection. Common practice is to dilute the stock to a more practical injection volume (e.g., 100µL subcutaneous). See injection volume calculation below.

Injection Volume Adjustment

For subcutaneous injection in rats: typical volume is 50–200µL per site.

Adjusted approach: Dilute stock to achieve 50–200µL injection volume for your dose.

If you need to deliver 3µg in 100µL:

Target concentration = 3µg / 0.1mL = 30µg/mL

Prepare working solution at 30µg/mL. Inject 100µL per animal.

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Step 7: Serial Dilution Series (Dose-Response Experiments)

For dose-response studies, you need a series of concentrations typically spanning 2–3 orders of magnitude. Serial dilutions are the standard approach.

1:10 Serial Dilution Example

Starting stock: 5mg/mL

Target: 5mg/mL, 500µg/mL, 50µg/mL, 5µg/mL, 0.5µg/mL (5 concentrations)

Step-by-step:

1. Stock: 5mg/mL = 5,000µg/mL

2. Transfer 100µL into 900µL diluent → 500µg/mL (1:10 dilution)

3. Transfer 100µL from #2 into 900µL diluent → 50µg/mL

4. Transfer 100µL from #3 into 900µL diluent → 5µg/mL

5. Transfer 100µL from #4 into 900µL diluent → 0.5µg/mL

Each step is a 10x dilution. Final series: 5000, 500, 50, 5, 0.5 µg/mL (or 5000, 500, 50, 5, 0.5 after step 1).

1:2 Serial Dilution (Half-log spacing)

For finer dose-response resolution, use 1:2 dilutions:

100µL + 100µL diluent = 200µL at half the previous concentration

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Common Calculation Mistakes and How to Avoid Them

Mistake 1: Confusing mg/mL with µg/mL

If you calculated a stock as 5mg/mL but recorded it as 5µg/mL, every subsequent dilution is off by 1,000x. This can look like the compound has no effect (if you're working at 1,000x below effective dose) or catastrophic effect (if 1,000x above).

Prevention: Always write units explicitly. Double-check conversions with a fresh eye before proceeding.

Mistake 2: Not Accounting for Diluent Volume

When adding diluent to a stock, the total volume is stock + diluent, not just diluent.

Wrong: "Add 10mL diluent to 1mL stock" → assumes final concentration = C₁ × (1/10)

Correct: Total volume = 10mL + 1mL = 11mL → concentration = C₁ × (1/11)

For most research where you add a small volume of stock to a much larger volume, this is negligible. But for high-concentration stocks with smaller dilutions, the error matters.

Mistake 3: Using Labeled Weight Instead of Net Peptide Content

As discussed above, a "5mg vial" is rarely exactly 5mg of peptide. Account for net peptide content when high dosing accuracy is required.

Mistake 4: Forgetting Aliquot Concentration Changes After Freeze-Thaw

If you freeze-thaw aliquots and some solution evaporates from poor vial sealing, concentration increases. Always use capped, sealed cryovials. Avoid uncapped or loosely capped storage.

Mistake 5: pH-Dependent Volume Changes

Some highly acidic or basic reconstitution solutions have slightly different volumes than expected. This is minor for most research but worth noting for highly precise work.

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Quick Reference: Worked Examples Summary

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Using Our Online Calculator

For quick calculations without manual math, use the Peptide Dosing Calculator which handles:

• •Reconstitution volume calculation
• •mg/mL ↔ µg/mL ↔ nM conversion
• •Body weight-based dose calculation
• •Dilution series generation
• •Net peptide content correction

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Dosing Calculation Checklist

Before preparing any solution:

• •[ ] Know exact weight of peptide in vial (including net peptide content if available)
• •[ ] Identify target concentration (and units — mg/mL, µg/mL, nM, etc.)
• •[ ] Calculate reconstitution volume = weight / target concentration
• •[ ] Prepare reconstitution vehicle (bacteriostatic water, sterile water, or appropriate vehicle)
• •[ ] Reconstitute and record actual volume used
• •[ ] Calculate working dilutions using C₁V₁ = C₂V₂
• •[ ] Verify units throughout — write them out explicitly
• •[ ] Label all vials with: compound name, lot number, concentration, date prepared, preparer initials

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Related Resources

• •Peptide Dosing Calculator — Online calculation tool
• •How to Reconstitute Peptides — Step-by-step guide
• •Bacteriostatic vs Sterile Water — Choosing your reconstitution vehicle
• •Peptide Storage Guide — Maintaining concentration accuracy long-term
• •Peptide Half-Lives Guide — For designing dosing intervals

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For research purposes only. This mathematical guide is for laboratory use in scientific research contexts. Not medical dosing guidance.

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Advanced Dosing Concepts

Molar Equivalency Across Related Compounds

When comparing research results across studies using different but related compounds, molar equivalency is often more meaningful than mass equivalency. Example:

To compare BPC-157 (MW ~1,419 Da) at 10µg/kg with TB-500 (MW ~4,964 Da) at an equivalent molar dose:

Step 1: Convert BPC-157 dose to nanomoles/kg:

10 µg/kg ÷ 1,419 g/mol = 10 µg/kg ÷ 1,419 µg/nmol = 0.00705 nmol/µg × 10 = 7.05 nmol/kg

Step 2: Convert to TB-500 mass equivalency at the same molar dose:

7.05 nmol/kg × 4,964 µg/nmol = 35,000 µg/kg = 35 µg/kg TB-500

So 10µg/kg BPC-157 ≈ 35µg/kg TB-500 on a molar basis.

Volume Constraints in Animal Models

Maximum injectable volumes by route and species (general guidelines):

These volume constraints determine your minimum working concentration. If delivering 3µg to a mouse in max 500µL SC:

Minimum concentration = 3µg ÷ 0.5mL = 6µg/mL minimum

Converting Published Human Doses to Rodent Research Doses

Published research often expresses doses as mg/kg (rodent) that bear no simple relationship to human clinical doses. Key reasons:

• •Allometric scaling (metabolic rate differences)
• •Route of administration differences
• •Species receptor sensitivity differences

Use published preclinical literature — not human clinical doses — as your starting point for rodent research. Never extrapolate clinical human doses directly to rodent research protocols.

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Peptide Concentration Verification Methods

Independent Concentration Verification

For high-stakes experiments, verify your reconstituted peptide concentration independently:

UV absorbance (A280): If your peptide contains Trp or Tyr residues, absorbance at 280 nm gives an extinction coefficient-based concentration estimate. Calculate using:

Beer-Lambert: A = ε × c × l

Where ε = molar extinction coefficient (calculate from sequence using ProtParam or similar tools), c = concentration (mol/L), l = path length (1 cm for standard cuvette)

Limitation: Peptides without aromatic residues (no Trp or Tyr) cannot be measured at A280 reliably.

A205 method: All peptides absorb at ~205 nm (peptide bond absorption). Less specific but applicable to all peptides. Background solvent absorption must be corrected.

BCA or Bradford protein assay: Can be adapted for peptides at high concentration. Requires standards with your specific peptide for accurate results.

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Reporting Dosing Information in Research

Documentation Standards

When reporting dosing in research records or publications:

1. State both mass and molar concentration: e.g., "5mg/mL (3.52 mM) BPC-157"

2. Note reconstitution vehicle: e.g., "in bacteriostatic water (pH 5.5)"

3. State delivered dose: mass/kg and molar dose

4. Note lot number and vendor: for reproducibility

5. Note net peptide content correction if applied

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For research purposes only. All peptide calculations and protocols are for laboratory research use. Not medical dosing guidance.

Molar Concentration Calculations for Peptide Research

Many in vitro research protocols specify concentrations in molar units (nM, µM) rather than mass units (mg/mL, µg/mL). Converting between the two requires knowing the molecular weight of the peptide.

The Formula

Molar concentration (nM) = (mass concentration in µg/mL × 1,000,000) ÷ molecular weight (Da)

Or equivalently:

Molar concentration (µM) = (mass concentration in mg/mL × 1,000) ÷ molecular weight (Da)

Worked Example: BPC-157 at 1 µM

BPC-157 molecular weight: 1,419.53 Da

Target: 1 µM (1,000 nM) working solution for cell culture

Step 1: Convert target to µg/mL

• •1 µM × 1,419.53 Da = 1,419.53 µg/mL = 1.42 mg/mL

Step 2: Prepare stock solution at convenient concentration

• •Reconstitute 5mg BPC-157 in 1.0mL bacteriostatic water → 5mg/mL stock

Step 3: Calculate dilution to reach 1.42 mg/mL working solution

• •C₁V₁ = C₂V₂
• •5mg/mL × V₁ = 1.42mg/mL × 10mL
• •V₁ = 2.84mL of stock
• •Add to 7.16mL of cell culture medium = 10mL total

Worked Example: Ipamorelin at 100 nM

Ipamorelin molecular weight: 711.87 Da

Step 1: Convert 100 nM to µg/mL

• •100 nM = 0.1 µM
• •0.1 µM × 711.87 Da = 71.19 µg/mL = 0.0712 mg/mL

Step 2: Working backward from a 2mg/mL stock:

• •C₁V₁ = C₂V₂
• •2mg/mL × V₁ = 0.0712mg/mL × 10mL
• •V₁ = 0.356mL (356µL of stock into 9.644mL medium)

Quick Conversion Table: Mass ↔ Molar (for 1mg/mL stock)

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Body Weight-Based Dosing Calculations

Preclinical research often expresses doses in terms of body weight (mg/kg or µg/kg). Converting these to actual volumes requires knowing both the animal weight and your stock concentration.

The Formula

Volume to administer (mL) = (dose in mg/kg × body weight in kg) ÷ stock concentration in mg/mL

Worked Example: Rodent Study at 250 µg/kg

Peptide: TB-500

Stock concentration: 1mg/mL (1,000 µg/mL)

Animal: 25g mouse = 0.025kg

Dose: 250 µg/kg

Step 1: Calculate total dose

• •250 µg/kg × 0.025kg = 6.25 µg total

Step 2: Calculate volume from stock

• •6.25 µg ÷ 1,000 µg/mL = 0.00625mL = 6.25 µL

Important note: 6.25 µL is a very small volume to measure accurately. Consider preparing a more dilute stock for rodent work, or use a dilution approach:

Option: Dilute stock 10-fold first

• •1mg/mL stock → add 100µL stock to 900µL vehicle = 0.1mg/mL (100µg/mL)
• •6.25µg ÷ 100µg/mL = 62.5µL → easier to measure accurately

Maximum Injection Volumes by Route (Rodent Reference)

Dose volume should stay within these limits to minimize confounding variables from injection volume effects.

Per-kg Dosing: Scaling Across Body Weights

When multiple animals of different weights are used, calculate each injection volume individually:

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Purity Correction: Accounting for Non-Peptide Mass

Peptide certificates of analysis typically report purity as a percentage of the chromatographic peak area. A "98% pure" peptide still contains 2% impurities — and the labeled vial weight includes both the peptide and impurities.

Why Purity Correction Matters

For most research applications, the 1-5% impurity contribution is acceptable and purity correction is optional. However, for:

• •Precise dose-response studies where accurate concentration matters
• •Binding assays requiring exact molar equivalents
• •Comparative studies across batches with different purities

...purity correction improves data quality.

The Correction Formula

Actual peptide mass = labeled mass × (purity% ÷ 100)

Corrected concentration = (actual peptide mass ÷ reconstitution volume)

Example: 5mg Vial at 97.3% Purity

Labeled weight: 5mg

Purity: 97.3%

Reconstitution volume: 1.0mL

Without correction: 5mg/mL stock concentration

With correction: 5mg × 0.973 = 4.865mg → 4.865mg/mL

The difference is 2.7% — significant for precision research but negligible for exploratory studies.

Counter-Ion Weight Correction

Many peptides are supplied as acetate or TFA (trifluoroacetate) salts. The salt contributes to the total weight but contains no pharmacological activity. For highly precise work:

• •Acetate (CH₃COO⁻): MW = 59 Da — adds ~5-15% extra weight for typical peptides
• •TFA (CF₃COO⁻): MW = 113 Da — adds ~10-25% extra weight

Most peptide vendors account for this in their purity/content calculations, but always verify by checking whether the CoA reports "peptide content by weight" separately from "purity by HPLC."

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Lab Documentation Standards for Dosing Records

Accurate dosing records are fundamental to reproducible research. Here is the minimum documentation standard for any peptide preparation:

Required Fields for Each Preparation

1. Date prepared: ISO format (YYYY-MM-DD) is recommended

2. Compound: Full name + catalog/lot number

3. Labeled mass: As printed on vial (mg)

4. Purity (if known): From CoA

5. Net peptide content (if known): From CoA

6. Reconstitution vehicle: BAC water, sterile saline, DMSO, etc.

7. Volume added: Exact volume (µL or mL)

8. Final concentration: With units

9. Storage conditions: Temperature, protection from light

10. Aliquot scheme: Volume per aliquot, number of aliquots

11. Prepared by: Initials or full name

Sample Lab Notebook Entry

Date: 2026-03-15
Compound: BPC-157, Lot A2024-031
Source: [vendor name]
Labeled mass: 5mg per CoA
Purity: 98.4% (HPLC)
Net peptide content: 4.92mg (estimated, purity × labeled)
Vehicle: Bacteriostatic water (0.9% benzyl alcohol)
Volume added: 1.0mL (1,000µL)
Final concentration: ~4.92mg/mL (purity-corrected) = ~4.92mg/mL stock
Aliquots: 10 × 100µL in cryovials, labeled BPC-157_A2024-031_4.92mgmL_20260315
Storage: -20°C freezer, drawer B
Prepared by: [initials]

Concentration Verification

For high-stakes research, verify actual concentration after reconstitution using:

• •UV spectrophotometry: At 280nm if the peptide contains aromatic residues (Trp, Tyr, Phe)
• •BCA or Bradford assay: For general protein/peptide quantification (less accurate for short peptides)
• •NanoDrop: Rapid UV method requiring minimal sample volume
• •HPLC quantification: Most accurate, uses external standard curve

Note that many research peptides (<10 amino acids) have low extinction coefficients at 280nm and may be better measured by other methods.

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Summary: The Dosing Calculation Workflow

1. Start with labeled weight → adjust for purity/content if precision required

2. Choose target concentration → based on protocol requirements and injection volume constraints

3. Calculate reconstitution volume = weight ÷ target concentration

4. Reconstitute carefully → add diluent slowly, do not vortex

5. Calculate working dilutions → using C₁V₁ = C₂V₂

6. Convert units if needed → molar ↔ mass using molecular weight

7. Scale for body weight → total dose = dose per kg × animal weight; volume = dose ÷ concentration

8. Document everything → compound, lot, concentration, date, preparer

9. Label all vials → before storing or using

Following this workflow consistently eliminates the most common dosing errors and ensures that concentration data is traceable and reproducible across experiments.

For additional reference tools:

• •Peptide Reconstitution Guide — step-by-step reconstitution
• •Certificate of Analysis Guide — reading purity and content data
• •Bacteriostatic vs Sterile Water — choosing the right vehicle
• •Peptide Solubility Guide — when standard vehicles fail

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Frequently Asked Questions About Peptide Dosing Math

How do I calculate how much bacteriostatic water to add to a peptide vial?

Use this formula: Volume to Add (mL) = Vial Size (mg) ÷ Target Concentration (mg/mL). For example, if you have a 5mg BPC-157 vial and want a concentration of 1mg/mL (1000mcg/mL), add 5mL of bacteriostatic water. For a higher concentration of 2.5mg/mL, add 2mL. Always use the Peptides.SO Reconstitution Calculator to avoid arithmetic errors.

How many mcg are in 1mg?

There are 1,000 micrograms (mcg) in 1 milligram (mg). Research peptide doses are typically expressed in micrograms, while vial sizes are expressed in milligrams. Converting between them is essential for accurate dosing. Example: a 5mg vial contains 5,000mcg of peptide.

How do I read an insulin syringe for peptide dosing?

U-100 insulin syringes hold 1mL and have 100 unit markings. Each unit = 0.01mL. To find what volume you need, use this: Syringe Units = Target Volume (mL) × 100. For example, if you need 0.1mL, that's 10 units on the syringe. If you need 0.05mL, that's 5 units. The smaller the syringe (1/2cc = 50 units, 3/10cc = 30 units), the finer the gradations and the more accurate your dose.

What is the difference between mcg and IU for peptides?

Micrograms (mcg) measure mass — the actual weight of the peptide compound. International Units (IU) are a biological activity measure used for some hormones (like HGH). For most research peptides (BPC-157, TB-500, ipamorelin, CJC-1295), doses are expressed in micrograms. GH secretagogues are sometimes expressed in IU when referencing GH response, but the peptide dose itself is still mcg/mg. Do not confuse IU on insulin syringes (which means syringe volume units) with biological IU.

How do I calculate how many doses are in a vial?

Total Doses = Vial Size (mcg) ÷ Dose Per Use (mcg). Example: 5mg vial = 5,000mcg. If each dose is 250mcg, then 5,000 ÷ 250 = 20 doses per vial. This calculation doesn't account for any dead volume in the vial or syringe waste — in practice, expect to get 90–95% of the theoretical dose count.

What concentration should I reconstitute my peptide at?

The optimal concentration depends on your target dose and syringe precision. A practical guideline: aim for a concentration where your dose volume falls between 0.05–0.2mL (5–20 units on a U-100 insulin syringe). Volumes smaller than 0.05mL are difficult to measure accurately; larger volumes per dose can be unnecessarily bulky. Use the calculator to find the concentration that gives you the most convenient dose volume.

How do I convert mg/mL to mcg/mL?

1 mg/mL = 1,000 mcg/mL. If you've reconstituted a 5mg peptide in 2mL of bacteriostatic water, the concentration is 2.5mg/mL = 2,500mcg/mL. To find the volume per dose: Dose Volume (mL) = Dose (mcg) ÷ Concentration (mcg/mL). Example: 500mcg dose ÷ 2,500mcg/mL = 0.2mL = 20 units on U-100 syringe.

Why does my peptide dose calculation give a different answer than the syringe shows?

Common sources of discrepancy: (1) confusing the concentration in mg/mL vs. mcg/mL, (2) misreading syringe units as mL (remember: 10 units on U-100 syringe = 0.1mL, not 10mL), (3) using the wrong vial size (check the COA for actual peptide content, not just nominal vial size). Always double-check your math by reversing the calculation: multiply your measured dose volume by concentration and verify you get your intended dose in mcg.

Is there a free calculator for peptide dosing math?

Yes — the Peptides.SO Dosage Calculator handles all conversions: enter your vial size, reconstitution volume, and target dose to get instant results in mL and syringe units. The Reconstitution Calculator helps determine how much bacteriostatic water to add. Both tools are free and require no registration.

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For research purposes only. This article is educational and does not constitute medical advice. Research peptides are not approved for human therapeutic use.

References:

1. Avvakumov GV, et al. "Quantitative peptide analysis by mass spectrometry." Journal of the American Society for Mass Spectrometry. 2012;23(11):2042–2051.

2. Gill SC, von Hippel PH. "Calculation of protein extinction coefficients from amino acid sequence data." Analytical Biochemistry. 1989;182(2):319–326. doi:10.1016/0003-2697(89)90026-5

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Further Reading:

• •How to Travel with Research Peptides: Storage, Shipping & International Guide
• •How to Store Research Peptides — Temperature, Stability & Shelf Life Guide
• •Peptide Solubility and Solvent Selection: A Practical Research Guide
• •How to Reconstitute Peptides: Ultimate Guide with Visual Diagrams + Calculator
• •Reconstitution Calculator
• •Peptide Stack Builder