Peptide Dosing Calculations for Research: Concentrations, Conversions, and Worked Examples

Why Dosing Math Matters

Accurate dosing calculations are the foundation of reproducible peptide research. An error in concentration math, unit conversion, or volume measurement can produce results that are meaningless at best and harmful at worst. This guide walks through the essential calculations that every peptide researcher should be comfortable performing, with worked examples at each step.

Basic Concentration Calculations

The Core Formula

The concentration of a reconstituted peptide is determined by two values:

Concentration (mg/mL) = Mass of peptide (mg) / Volume of solvent (mL)

This is the single most important formula in peptide preparation. Everything else builds on it.

Worked Example 1: Standard Reconstitution

You have a vial containing 5 mg of BPC-157 and add 2 mL of bacteriostatic water.

Concentration = 5 mg / 2 mL = 2.5 mg/mL

This means every 1 mL of solution contains 2.5 mg of peptide. Every 0.1 mL contains 0.25 mg (250 mcg).

Choosing a Reconstitution Volume

The volume of solvent you add determines the concentration. Choosing the right volume involves balancing two factors:

Higher concentration (less solvent): Allows smaller injection volumes, but requires more precise measurement and may exceed the peptide’s solubility limit
Lower concentration (more solvent): Easier to measure accurately, but requires larger injection volumes and the vial will be depleted faster

Vial Size	1 mL Added	2 mL Added	3 mL Added	5 mL Added
2 mg	2 mg/mL	1 mg/mL	0.67 mg/mL	0.4 mg/mL
5 mg	5 mg/mL	2.5 mg/mL	1.67 mg/mL	1 mg/mL
10 mg	10 mg/mL	5 mg/mL	3.33 mg/mL	2 mg/mL

Unit Conversions

Peptide doses are expressed in various units depending on the context. Being fluent in these conversions prevents errors.

Mass Conversions

From	To	Multiply By
Milligrams (mg)	Micrograms (mcg or ug)	1,000
Micrograms (mcg)	Milligrams (mg)	0.001
Grams (g)	Milligrams (mg)	1,000
Milligrams (mg)	Grams (g)	0.001

Key equivalences:

1 mg = 1,000 mcg
0.1 mg = 100 mcg
0.01 mg = 10 mcg
0.25 mg = 250 mcg

Volume Conversions

From	To	Multiply By
Milliliters (mL)	Units on insulin syringe (1 mL = 100 units)	100
Units on insulin syringe	Milliliters (mL)	0.01
Milliliters (mL)	Cubic centimeters (cc)	1 (they are equal)

International Units (IU)

Some peptides (particularly HGH and HCG) are measured in International Units rather than mass. The conversion between IU and mg is peptide-specific and depends on the biological assay used to define the unit.

Calculating Dose Volumes

Once your peptide is reconstituted, you need to calculate how much solution to draw for each dose.

The Formula

Volume to draw (mL) = Desired dose (mg) / Concentration (mg/mL)

Worked Example 2: BPC-157 Dosing

Concentration: 2.5 mg/mL (5 mg peptide in 2 mL BAC water)
Desired dose: 250 mcg (0.25 mg)

Volume = 0.25 mg / 2.5 mg/mL = 0.1 mL = 10 units on a 100-unit insulin syringe

Worked Example 3: Ipamorelin Dosing

Concentration: 2 mg/mL (5 mg peptide in 2.5 mL BAC water)
Desired dose: 200 mcg (0.2 mg)

Volume = 0.2 mg / 2 mg/mL = 0.1 mL = 10 units on a 100-unit insulin syringe

Worked Example 4: Higher Dose

Concentration: 5 mg/mL (10 mg peptide in 2 mL BAC water)
Desired dose: 1 mg

Volume = 1 mg / 5 mg/mL = 0.2 mL = 20 units on a 100-unit insulin syringe

Reading an Insulin Syringe

The standard 1 mL insulin syringe is divided into 100 units, where each unit equals 0.01 mL. Understanding this scale is critical for accurate dosing.

Scale Reference

Units on Syringe	Volume (mL)	Volume (cc)
5 units	0.05 mL	0.05 cc
10 units	0.10 mL	0.10 cc
15 units	0.15 mL	0.15 cc
20 units	0.20 mL	0.20 cc
25 units	0.25 mL	0.25 cc
50 units	0.50 mL	0.50 cc
100 units	1.00 mL	1.00 cc

Tips for Accurate Measurement

Read the syringe at eye level with the needle pointing upward
Align the flat edge of the plunger rubber stopper with the desired mark (not the curved edge)
Expel air bubbles before measuring the final volume
Draw slightly past the target line, then push back to it for precision

Adjusting for Peptide Content

As discussed in our purity testing guide, the labeled weight of a peptide vial includes counterions, residual moisture, and salts. The actual peptide content is typically 60-85% of the gross weight.

When to Adjust

For most research purposes, researchers use the labeled weight without adjustment, as the standard dosing references in the literature typically assume gross weight. However, for highly precise pharmacokinetic studies, you may want to adjust:

Actual peptide mass = Labeled weight x (Peptide content % / 100)

Worked Example 5: Peptide Content Adjustment

Vial labeled as 5 mg
COA states peptide content: 78%
Actual peptide = 5 mg x 0.78 = 3.9 mg
Reconstituted in 2 mL: Adjusted concentration = 3.9 mg / 2 mL = 1.95 mg/mL

Dilution Calculations

Sometimes a stock solution is too concentrated for accurate measurement, and you need to prepare a diluted working solution.

The Dilution Formula

C1 x V1 = C2 x V2

Where:

C1 = initial (stock) concentration
V1 = volume of stock solution needed
C2 = desired (final) concentration
V2 = desired final volume

Worked Example 6: Preparing a Diluted Working Solution

Stock concentration (C1): 5 mg/mL
Desired concentration (C2): 1 mg/mL
Desired final volume (V2): 1 mL

V1 = (C2 x V2) / C1 = (1 mg/mL x 1 mL) / 5 mg/mL = 0.2 mL

Take 0.2 mL of stock solution and add 0.8 mL of bacteriostatic water to obtain 1 mL at 1 mg/mL.

Allometric Scaling from Animal Models

When translating doses between species (e.g., from published rodent studies to other models), simple weight-based scaling (mg/kg) often underestimates or overestimates the appropriate dose. Allometric scaling uses body surface area (BSA) to account for metabolic differences between species.

The FDA BSA Conversion Method

The standard approach uses species-specific conversion factors (Km values):

Human Equivalent Dose (mg/kg) = Animal dose (mg/kg) x (Animal Km / Human Km)

Standard Km Values

Species	Average Weight (kg)	Km Factor
Mouse	0.02	3
Rat	0.15	6
Rabbit	1.8	12
Dog	10	20
Human	60	37

Worked Example 7: Mouse to Human Scaling

Published mouse dose: 10 mcg/kg
Mouse Km = 3
Human Km = 37

Human Equivalent Dose = 10 mcg/kg x (3 / 37) = 0.81 mcg/kg

A mouse dose of 10 mcg/kg scales to approximately 0.81 mcg/kg in a human-equivalent calculation. For a 70 kg human, this would be approximately 57 mcg total.

Quick Reference: Common Research Concentrations

Peptide	Typical Vial	Common Reconstitution	Concentration	Common Research Dose	Volume per Dose
BPC-157	5 mg	2 mL BAC water	2.5 mg/mL	250 mcg	0.1 mL (10 units)
Ipamorelin	5 mg	2.5 mL BAC water	2 mg/mL	200 mcg	0.1 mL (10 units)
TB-500	5 mg	1 mL BAC water	5 mg/mL	2.5 mg	0.5 mL (50 units)
Sermorelin	2 mg	2 mL BAC water	1 mg/mL	200 mcg	0.2 mL (20 units)

Summary

Peptide dosing calculations are straightforward arithmetic, but precision matters enormously. The essential skills are: calculating reconstitution concentrations, converting between mass units, determining dose volumes from concentrations, reading a syringe accurately, and understanding when and how to apply allometric scaling. By mastering these calculations and double-checking your math before every preparation, you ensure that the dose reaching the experimental system is exactly what you intended.