Peptide Dose Calculator
How many units is your dose? Enter the dose in mg or mcg, your vial amount, and the bacteriostatic water you added — this free peptide dose calculator converts it into the exact units to draw on a U-100 or U-40 insulin syringe, with the concentration and doses-per-vial worked out too.
100 units per mL — pick the syringe you have.
Draw to
BAC water
on a U-100 insulin syringe
Drag the syringe to set your dose, or type the values above.
Enter your vial amount and dose, then type the bacteriostatic water or drag the syringe to see the exact units to draw.
Never do this math twice.
The Pep AI app remembers your vials and doses, shows an interactive syringe you draw to, counts down the doses left in each vial, and reminds you when it's time. Free on iOS and Android.
How the dose calculator works
A dose in mg or mcg has to become a line on a syringe. That takes three conversions, and the calculator does all of them from your numbers:
1. Concentration
Vial amount ÷ water added. A 5 mg vial with 2 mL of water is 2.5 mg/mL.
2. Volume per dose
Your dose ÷ concentration. A 1 mg dose at 2.5 mg/mL is 0.4 mL.
3. Units to draw
Volume per dose × 100 for a U-100 syringe (or × 40 for a U-40). 0.4 mL on a U-100 syringe is 40 units.
Worked example
You have a 5 mg vial, you want a 1 mg dose, and you add 2 mL of bacteriostatic water. Concentration is 5 ÷ 2 = 2.5 mg/mL. Volume per dose is 1 ÷ 2.5 = 0.4 mL. On a U-100 syringe that's 0.4 × 100 = 40 units, and the vial holds 5 doses.
mg, mcg, and units — what's actually being converted
The confusion behind almost every dosing mistake is that mg and mcg measure mass, while syringe units measure volume. There is no fixed answer to "how many units is 1 mg" — it depends entirely on how concentrated your vial is after reconstitution. The same 1 mg dose might be 10 units in one vial and 40 in another.
That's why this calculator asks for the vial amount and the water you added, not just the dose. Those two numbers set the concentration (mg/mL); the dose divided by the concentration gives the volume; and the volume times the syringe scale (100 units per mL on a U-100) gives the units to draw.
Also worth knowing: 1 mg equals 1,000 mcg. Compounds dosed in micrograms — BPC-157 is the classic case — are where unit mix-ups hurt most, so the calculator has an mg/mcg toggle on both the vial and the dose field.
Frequently asked questions
This calculator is provided for informational and educational purposes only and is not medical advice. Always confirm dosing with a qualified healthcare professional and double-check your own measurements before administering anything.