Laboratory Protocols • February 14, 2026

Peptide Reconstitution Calculator: How to Calculate Concentration After Mixing

A step-by-step guide to calculating peptide concentration after reconstitution, with worked examples for common research peptides and unit conversion references.

Part of the PeptidesATX Research Hub

Why Accurate Peptide Calculations Matter

Precision in peptide research begins with accurate concentration calculations. When a lyophilized peptide is reconstituted with bacteriostatic water, the resulting solution must be at a known concentration to ensure reproducible experimental outcomes. Even small errors in calculation can compound across multiple administrations, leading to inconsistent data, wasted reagents, and compromised study integrity.

This peptide reconstitution calculator guide provides the formulas, unit conversions, and worked examples you need to accurately determine concentration after mixing. Whether you are working with BPC-157, Tirzepatide, CJC/Ipamorelin, or Tesamorelin, the same fundamental formula applies. All calculations described here are intended for laboratory research use only.

The Basic Formula: Concentration = Mass ÷ Volume

Every peptide concentration calculator relies on a single core formula:

Concentration (mg/mL) = Total Peptide Mass (mg) ÷ Volume of Solvent (mL)

This formula is universal. Regardless of the peptide, the supplier, or the reconstitution solvent, concentration is always determined by dividing the total mass of peptide by the total volume of liquid added. The mass is found on the vial label or the Certificate of Analysis (COA), and the volume is the amount of bacteriostatic water you add during reconstitution.

Once you have the concentration in mg/mL, you can convert to mcg/mL by multiplying by 1,000 (since 1 mg = 1,000 mcg). From there, determining the draw volume for a specific dose is straightforward: divide the desired dose by the concentration.

Volume to Draw (mL) = Desired Dose (mcg) ÷ Concentration (mcg/mL)

Understanding Units: mg, mcg, mL, IU, and Insulin Syringe Units

Before performing calculations, it is essential to understand the units involved in peptide research:

mg (milligrams): One thousandth of a gram. Peptide vials are typically labeled in mg (e.g., 5 mg, 10 mg).
mcg (micrograms): One thousandth of a milligram, or one millionth of a gram. Research doses are often expressed in mcg. 1 mg = 1,000 mcg.
mL (milliliters): A unit of volume. Reconstitution volumes are measured in mL.
IU (International Units): A measurement based on biological activity rather than mass. IU conversions are peptide-specific and defined by international standards. Not all peptides use IU.
Units on an insulin syringe: A U-100 insulin syringe reads in "units" where 100 units = 1 mL. Therefore, 1 unit = 0.01 mL. This is a volume measurement, not a dose measurement. Do not confuse syringe units with IU.

Keeping these distinctions clear is critical. The most common source of calculation errors in peptide research is confusing syringe units (a volume measure) with International Units (a biological potency measure).

Step-by-Step Calculation Examples

The following examples demonstrate how to apply the concentration formula to commonly used research peptides. Each example walks through the full process from reconstitution to determining draw volume for a specific research dose.

Example 1: BPC-157 5 mg Vial + 1 mL BAC Water

Given: A BPC-157 vial containing 5 mg of lyophilized peptide, reconstituted with 1 mL of bacteriostatic water.

Concentration: 5 mg ÷ 1 mL = 5 mg/mL (or 5,000 mcg/mL)
For a 250 mcg dose: 250 mcg ÷ 5,000 mcg/mL = 0.05 mL = 5 units on a U-100 insulin syringe
For a 500 mcg dose: 500 mcg ÷ 5,000 mcg/mL = 0.10 mL = 10 units on a U-100 insulin syringe

At this concentration, the vial contains enough peptide for twenty 250 mcg research doses or ten 500 mcg research doses.

Example 2: BPC-157 10 mg Vial + 2 mL BAC Water

Given: A BPC-157 vial containing 10 mg of lyophilized peptide, reconstituted with 2 mL of bacteriostatic water.

Concentration: 10 mg ÷ 2 mL = 5 mg/mL (or 5,000 mcg/mL)
For a 250 mcg dose: 250 mcg ÷ 5,000 mcg/mL = 0.05 mL = 5 units on a U-100 insulin syringe
For a 500 mcg dose: 500 mcg ÷ 5,000 mcg/mL = 0.10 mL = 10 units on a U-100 insulin syringe

Note that doubling both the mass and the volume produces the same concentration as Example 1 (5 mg/mL). The difference is total vial capacity: this vial provides forty 250 mcg research doses instead of twenty.

Example 3: Tirzepatide 10 mg Vial + 1 mL BAC Water

Given: A Tirzepatide vial containing 10 mg of lyophilized peptide, reconstituted with 1 mL of bacteriostatic water.

Concentration: 10 mg ÷ 1 mL = 10 mg/mL (or 10,000 mcg/mL)
For a 2,500 mcg (2.5 mg) dose: 2,500 mcg ÷ 10,000 mcg/mL = 0.25 mL = 25 units on a U-100 insulin syringe
For a 5,000 mcg (5 mg) dose: 5,000 mcg ÷ 10,000 mcg/mL = 0.50 mL = 50 units on a U-100 insulin syringe

With a 10 mg/mL concentration, this is a relatively concentrated solution. Researchers should use appropriately graduated syringes for accurate measurement at these volumes.

Example 4: CJC/Ipamorelin Blend + 2 mL BAC Water

Given: A CJC-1295/Ipamorelin blend vial containing 5 mg of each peptide (10 mg total blend), reconstituted with 2 mL of bacteriostatic water.

Total blend concentration: 10 mg ÷ 2 mL = 5 mg/mL total (2.5 mg/mL of each peptide)
Per-peptide concentration: 5 mg ÷ 2 mL = 2,500 mcg/mL of each peptide
For a 300 mcg dose of each peptide (600 mcg blend): 300 mcg ÷ 2,500 mcg/mL = 0.12 mL = 12 units on a U-100 insulin syringe

With blended peptides, it is important to track the per-peptide concentration rather than only the total. Since both peptides are drawn together in a single volume, the draw volume corresponds to the dose of each individual component.

Example 5: Tesamorelin 10 mg + 2 mL BAC Water

Given: A Tesamorelin vial containing 10 mg of lyophilized peptide, reconstituted with 2 mL of bacteriostatic water.

Concentration: 10 mg ÷ 2 mL = 5 mg/mL (or 5,000 mcg/mL)
For a 1,000 mcg (1 mg) dose: 1,000 mcg ÷ 5,000 mcg/mL = 0.20 mL = 20 units on a U-100 insulin syringe
For a 2,000 mcg (2 mg) dose: 2,000 mcg ÷ 5,000 mcg/mL = 0.40 mL = 40 units on a U-100 insulin syringe

This concentration allows for straightforward dose measurement with standard insulin syringes, making it a practical reconstitution volume for Tesamorelin research protocols.

Reading an Insulin Syringe: U-100 Scale and Converting Units to mL

Most peptide researchers use U-100 insulin syringes to measure and transfer reconstituted solutions. Understanding the scale is essential for accurate dosing:

U-100 means: The syringe is calibrated for 100 units per 1 mL
1 unit = 0.01 mL (one hundredth of a milliliter)
10 units = 0.10 mL
50 units = 0.50 mL
100 units = 1.00 mL

To convert a calculated mL volume to syringe units, simply multiply by 100. Conversely, to convert syringe units to mL, divide by 100. The conversion formula is:

Syringe Units = Volume in mL x 100

Common insulin syringes come in three sizes: 0.3 mL (30 units), 0.5 mL (50 units), and 1.0 mL (100 units). Choosing the smallest syringe that accommodates your draw volume provides the best accuracy. For example, if your calculated volume is 0.05 mL (5 units), a 0.3 mL syringe with its finer graduation marks will yield a more precise measurement than a 1.0 mL syringe.

Remember: the "units" on an insulin syringe are strictly a volume measurement. They do not represent International Units (IU) or any dose quantity. The actual dose depends entirely on the concentration of your reconstituted solution.

Common Calculation Mistakes

Accuracy in peptide concentration calculations requires attention to detail. The following mistakes are frequently encountered in laboratory settings:

Confusing mg and mcg: Forgetting to convert between milligrams and micrograms leads to 1,000-fold errors. Always confirm your units before calculating. 1 mg = 1,000 mcg.
Confusing syringe units with IU: Insulin syringe units measure volume (1 unit = 0.01 mL), not biological potency. Drawing "5 units" from a syringe does not mean 5 IU of peptide.
Using the wrong vial mass: Always refer to the Certificate of Analysis for the actual peptide content. Some vials may contain overfill, and the labeled mass should be verified against COA documentation.
Not accounting for dead volume: Syringes and needles retain a small amount of solution (dead volume). For precise work, researchers should account for this or use low dead-volume syringes.
Rounding too aggressively: Carry calculations to at least two decimal places before rounding the final draw volume. Premature rounding accumulates error across multiple doses.
Assuming all vials have the same concentration: Different vial sizes and reconstitution volumes produce different concentrations. Recalculate for each vial individually rather than relying on memory from previous preparations.

Dilution for Lower Concentrations

In some research protocols, a lower concentration may be desirable for easier measurement of small doses. Dilution is achieved simply by adding more bacteriostatic water during reconstitution. The total peptide mass remains the same; only the concentration changes.

For example, consider a 5 mg BPC-157 vial:

1 mL BAC water: 5 mg ÷ 1 mL = 5,000 mcg/mL (higher concentration, smaller draw volumes)
2 mL BAC water: 5 mg ÷ 2 mL = 2,500 mcg/mL (moderate concentration)
5 mL BAC water: 5 mg ÷ 5 mL = 1,000 mcg/mL (lower concentration, larger draw volumes)

Choosing a dilution volume is a balance between measurement precision and practicality. A higher concentration requires smaller draw volumes (harder to measure precisely), while a lower concentration requires larger draw volumes (easier to measure but depletes the vial faster per draw). Researchers should select the reconstitution volume that allows accurate measurement with their available syringes while maintaining a practical number of doses per vial.

For detailed reconstitution procedures, including aseptic technique and solvent handling, see our complete guide on how to reconstitute peptides. For information on maintaining peptide stability after mixing, refer to our article on how to store reconstituted peptides.

Frequently Asked Questions

How do you calculate peptide concentration after reconstitution?

To calculate peptide concentration after reconstitution, divide the total mass of lyophilized peptide (in mg or mcg) by the volume of solvent added (in mL). For example, a 5 mg vial reconstituted with 1 mL of bacteriostatic water yields a concentration of 5 mg/mL, or 5,000 mcg/mL. This formula (Concentration = Mass / Volume) applies universally regardless of peptide type.

How do you convert mcg to mL on an insulin syringe?

First, determine the concentration of your reconstituted solution (mcg/mL). Then divide the desired dose in mcg by the concentration in mcg/mL to get the volume in mL. To convert mL to insulin syringe units on a U-100 syringe, multiply the mL value by 100. For example, if your concentration is 5,000 mcg/mL and you need 250 mcg, that equals 0.05 mL, which is 5 units on a U-100 insulin syringe.

Does adding more bacteriostatic water change the total amount of peptide?

No. Adding more bacteriostatic water changes the concentration (mcg per mL) but does not change the total amount of peptide in the vial. A 5 mg vial still contains 5 mg of peptide regardless of whether it is reconstituted with 1 mL or 2 mL of solvent. More solvent simply means a lower concentration per unit volume, requiring a larger draw volume for the same dose.

What is the best volume of bacteriostatic water to use for reconstitution?

The optimal volume of bacteriostatic water depends on the desired concentration and the precision of your measuring instruments. Common reconstitution volumes range from 1 mL to 3 mL. Using less solvent yields a higher concentration (smaller draw volumes), while using more solvent yields a lower concentration (easier to measure precise doses). Researchers should choose a volume that allows accurate measurement with their available syringes.

Can you use a peptide reconstitution calculator for any peptide?

Yes. The Concentration = Mass / Volume formula is universal and applies to any lyophilized peptide, including BPC-157, Tirzepatide, CJC/Ipamorelin, Tesamorelin, and others. The only variables are the total mass of peptide in the vial and the volume of bacteriostatic water used for reconstitution. Always verify the labeled mass on your Certificate of Analysis before performing calculations.

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Disclaimer: All compounds referenced in this article are intended for laboratory research use only. They are not approved for human or veterinary use. This content is provided for educational and informational purposes and does not constitute medical advice.

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