🧬 Peptide Reconstitution Calculator

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How to Use This Calculator

1. Enter the peptide vial size — This is the total amount of lyophilized peptide in the vial, measured in milligrams (mg). Common sizes are 2mg, 5mg, and 10mg.
2. Enter the amount of bacteriostatic water — Input how many milliliters (mL) of BAC water you'll add to reconstitute the peptide. Common volumes are 1mL, 2mL, or 3mL — more water means less concentrated solution.
3. Enter your target dose in micrograms (mcg) — Specify the dose you want per injection. The calculator converts between mg and mcg and calculates the exact volume to draw in your syringe.
4. Review the IU and mL per dose — The calculator shows exactly how many IU or mL to draw for your target dose. It also shows the total number of doses per vial so you know how long one vial will last at your protocol.

Tips and Best Practices

→ Use this as a starting point, not a diagnosis. Online calculators provide estimates based on population averages. Your individual results may vary — consult a healthcare professional for personalized medical advice.

→ Measure consistently. For the most accurate tracking, take measurements at the same time of day under the same conditions each time you use this calculator.

→ Track trends, not single data points. One measurement is a snapshot. Track results over weeks and months to see meaningful patterns and progress.

→ Combine with related tools. Use this alongside other health calculators on this site for a more complete picture of your fitness and wellness metrics.

See also: GLP-1 Titration Tracker · Deep Work Capacity Calculator · Pace Calculator · Intermittent Fasting Calculator · Exercise Calorie Burn

What Is a Peptide Reconstitution Calculator?

A peptide reconstitution calculator takes the size of your peptide vial (in mg), the volume of bacteriostatic water you plan to add (in mL), and the dose you want to draw (in mcg or mg) and returns exactly how many "units" to draw on a standard insulin syringe. The conversion sounds simple but combines three different units of measurement that are easy to confuse in real time at the kitchen counter — milligrams of peptide, milliliters of solution, and "units" on a U-100 insulin syringe (where 100 units equals 1 mL). Doing this math by hand under fatigue is the most common source of accidental dose errors, particularly when scaling protocols up or down.¹

This calculator runs entirely in your browser — your inputs are not sent to any server, and no account is required. It supports BPC-157, TB-500, semaglutide, tirzepatide, retatrutide, CJC-1295 (with and without DAC), Ipamorelin, Sermorelin, IGF-1 LR3, GHK-Cu, melanotan II, epithalon, and 20+ other commonly-discussed research and clinical peptides. The math is identical across compounds; what differs is the typical dose range and the standard reconstitution volume that produces a comfortable syringe-draw size for that dose.

The Math: How Reconstitution Calculations Work

The core formula is: units to draw = (desired dose in mcg ÷ peptide concentration in mcg/mL) × 100. The concentration depends entirely on your reconstitution choice — a 5 mg vial diluted in 2 mL of bacteriostatic water yields 2,500 mcg/mL. To draw a 250 mcg dose at that concentration, you need 0.1 mL, which on a U-100 insulin syringe is 10 units. Drawing the same 250 mcg dose from a vial reconstituted in 5 mL (1,000 mcg/mL) instead requires 0.25 mL, or 25 units — much easier to measure precisely on the syringe scale.²

This trade-off is the most important reconstitution decision: more water means lower concentration, larger draws, and easier precision; less water means higher concentration, smaller draws, and longer vial life when doses are infrequent. The calculator helps you visualize this trade-off by showing what your specific dose looks like at different dilution choices.

Common Reconstitution Volumes by Peptide

*Volumes shown are common starting points used in research and reported clinical practice. Your specific protocol should come from your prescriber.

Worked Example: BPC-157

You have a 5 mg vial of BPC-157, and you plan to add 2 mL of bacteriostatic water. Your protocol calls for 250 mcg twice daily. Step by step:

1. Calculate concentration: 5 mg ÷ 2 mL = 2.5 mg/mL = 2,500 mcg/mL.
2. Convert dose to volume: 250 mcg ÷ 2,500 mcg/mL = 0.10 mL per injection.
3. Convert to insulin-syringe units: 0.10 mL × 100 units/mL = 10 units per injection.
4. Calculate doses per vial: 5,000 mcg ÷ 250 mcg = 20 doses (10 days at twice daily).

If your protocol later changed to 500 mcg twice daily, the math becomes: 500 mcg ÷ 2,500 mcg/mL = 0.20 mL = 20 units. Same vial, same concentration, twice the draw. The calculator updates this on the fly so you don't have to redo the arithmetic each time you adjust a protocol.

Why Bacteriostatic Water?

Bacteriostatic water (BAC water) contains 0.9% benzyl alcohol, a preservative that suppresses bacterial growth in a multi-puncture-use vial. Sterile water for injection has no preservative — the vial is sterile when manufactured, but once punctured, contamination risk rises with every additional draw. For a peptide vial that will be punctured 20+ times over 2–4 weeks, BAC water is the standard choice and the one most published research stability data is based on. A reconstituted vial with BAC water is typically stable for 25–30 days refrigerated; with sterile water, the same vial should be discarded within 24–48 hours of first puncture even if mathematically more doses remain.³

Benzyl alcohol toxicity has been documented in neonates at sustained high doses, which is why BAC water is contraindicated in newborns. For adult research-peptide protocols at typical doses, the daily benzyl alcohol exposure is far below any concerning threshold — a 1 mL injection from a BAC-water-reconstituted vial contains roughly 9 mg of benzyl alcohol, well below the cumulative limits seen in neonatal IV scenarios.

How to Add Water to a Lyophilized Vial

Technique matters here. Mishandled reconstitution is one of the more common ways to physically damage a peptide before it ever reaches the injection site. The standard procedure:

1. Wipe both vial septa (BAC water and lyophilized peptide) with an alcohol prep pad. Let dry 10 seconds.
2. Draw your planned water volume into a sterile syringe — typically a 3 mL syringe with a 22-gauge needle for transfers, NOT your insulin syringe.
3. Insert the needle into the peptide vial at an angle, with the vial held nearly horizontal so the water runs down the inner glass wall.
4. Inject slowly — over 5–10 seconds — letting the water trickle onto the powder rather than blasting it directly. Forceful injection can shear peptide chains.
5. Withdraw the needle. Do NOT shake. Gently roll or swirl the vial between your palms for 30–60 seconds until the powder fully dissolves. Some peptides take a few minutes; if visible particles remain after 5 minutes, gently invert the vial a few times.
6. Inspect. The solution should be clear and colorless (with rare exceptions like GHK-Cu, which is blue). Cloudiness, particles, or an unusual color means the vial should not be used.

Common Reconstitution Mistakes

Confusing mg with mcg. 1 mg = 1,000 mcg. A 250 mcg dose is one thousand times smaller than a 250 mg dose. Misreading a protocol can produce a 1,000× error in either direction. Always verify the unit symbol before drawing.

Using a U-40 syringe instead of U-100. Standard insulin syringes are U-100, where 100 units = 1 mL. U-40 syringes (used for some veterinary insulin) read differently — the same drawn volume corresponds to a different "unit" number. Verify that "U-100" is printed on your syringe before using.

Shaking the vial during reconstitution. Vigorous agitation produces foaming and shears peptide chains. Roll or gently swirl instead — full dissolution takes 30–60 seconds for most peptides, longer for some.

Reconstituting at too high a concentration for typical doses. If your protocol calls for 100 mcg doses and you reconstitute a 5 mg vial in 1 mL, your draw is 2 units — hard to measure precisely on the syringe scale. Diluting in 5 mL instead gives 10-unit draws, much easier to reproduce accurately.

Forgetting to factor reconstitution into dose math. The vial label says "5 mg" but you're injecting from a solution. Always work from concentration (mcg/mL) when computing volume, never from the raw vial size.