Free Tool · Updated 2026

Peptide Calculator

Standard reconstitution · Custom draw (reverse mode) · No other calculator has this

2,500
mcg / mL
10.0
Units to Draw
0.100
mL to Draw
20
Doses / Vial

Why Custom Draw Matters

Every other peptide calculator asks: "how much water did you add?" Then it tells you how many units to draw. That works — but only if you don't care which syringe mark you land on.

In practice, most users have a preferred draw point. 10 units on a U-100 syringe is easy to read accurately. 7 units is harder. 13 units is annoying. The Custom Draw calculator flips the logic: tell it the units you want to draw, and it tells you how much BAC water to add to hit that mark exactly. No other peptide calculator does this.

Example — BPC-157, 5mg vial, 250mcg dose

Standard mode: Add 2mL BAC water → draw 10 units. Clean, works well.

Custom Draw: You want exactly 20 units per dose for easier reading. Enter: 5mg · 250mcg · 20 units. Result: add 4mL BAC water. Concentration adjusts, dose stays correct, you get the syringe mark you want.

Small vials, low doses — where this really shines

Running 100mcg of a high-potency peptide from a 2mg vial? Standard mode might give you 4 units — barely a mark on the syringe. Custom Draw lets you set 10 units and work backwards to the right water volume. Precision where it matters most.

The Standard Calculations

Concentration (mcg/mL)

Peptide mg × 1,000 ÷ BAC water mL. This is the foundation. A 5mg vial with 2mL BAC water = 2,500 mcg/mL. Every other calculation depends on it.

Draw Volume

Target dose ÷ concentration. At 2,500 mcg/mL, a 250mcg dose = 0.100mL. On a U-100 syringe: 10 units.

Doses Per Vial

Total peptide in mcg ÷ dose size. A 5mg vial at 250mcg/dose = 20 doses. Track this in Protocol — you'll get a low-stock alert before running out.

BAC Water vs Sterile Water

Bacteriostatic water (0.9% benzyl alcohol) preserves your reconstituted peptide for 4+ weeks refrigerated. Sterile water has no preservative — use within 24–48 hours. For any multi-dose protocol, BAC water is the correct choice.

Take the Calculator With You

Protocol's mobile calculator includes both Standard and Custom Draw modes, saves your vial parameters, and logs every dose. Free on iOS and Android.

Download on the App Store Get it on Google Play

No account · On-device only · iOS + Android

Frequently Asked Questions

How much BAC water should I add?
Use Custom Draw mode to answer this precisely. Enter your vial size, target dose, and the syringe units you want to draw — the calculator tells you exactly how much BAC water to add. For a starting point without Custom Draw: 2mL per 5mg vial gives 2,500 mcg/mL, which puts a 250mcg dose at 10 units on a U-100 syringe.
What is Custom Draw mode?
Custom Draw is a reverse calculator: instead of "I added X water, what do I draw?" it answers "I want to draw Y units, how much water do I add?" Enter your peptide amount, target dose, and preferred draw units — it calculates the exact BAC water volume needed and confirms the dose is correct. No other peptide calculator has this.
What syringe should I use?
A U-100 insulin syringe (100 units per mL) is standard for peptide injections. The calculator defaults to 100 units/mL. If you use a U-40 syringe (40 units/mL), change the syringe field accordingly.
Can I track my reconstitutions in an app?
Yes. Protocol (iOS + Android) includes this calculator with both modes, saves vial parameters, tracks remaining doses, and logs each injection to your protocol automatically. Free to download.

Step-by-step guide: How to Reconstitute Peptides →

Common mistakes: Reconstitution FAQ →

Mobile calculator: free peptide calculator →

Also see: best peptide tracker app → · peptide calculator guide →