Get the dose exactly right.
A free peptide dosage calculator and reconstitution calculator. Enter your vial size and bacteriostatic water to get the precise concentration and how many units to draw on an insulin syringe, for semaglutide, tirzepatide, retatrutide, BPC-157, or any peptide. The same math built into the Peptide AI app, free to use here.
Already reconstituted? Enter your vial and water, then any dose, to see exactly how many insulin-syringe units to draw. This peptide dose calculator works for any compound: semaglutide, tirzepatide, retatrutide, BPC-157, ipamorelin and more.
Reconstituting two or more peptides in one vial? Enter each peptide's amount, the total BAC water, and how many units you'll inject to see the dose of each component.
Peptide doses are written in both milligrams (mg) and micrograms (mcg). 1 mg = 1000 mcg. Type in either box and the other updates.
A peptide's half-life is how long it takes for half of it to clear your bloodstream. Enter it in hours to see time to steady state, how much the peptide accumulates with repeated dosing, and a suggested dosing interval.
Ramp a GLP-1 dose up gradually to reduce side effects. Load a published schedule or build your own from a starting dose, target dose, and step size.
Insulin-syringe units assume a U-100 syringe (100 units = 1 ml, so 1 unit = 0.01 ml).
Educational tool only. Not medical advice. Verify every dose independently and consult a licensed provider.
How the peptide dosage & reconstitution calculator works
This free peptide dosage calculator and reconstitution calculator turns two numbers, your vial size and the amount of bacteriostatic water you add, into the answer that actually matters at the bench: how many units to draw on an insulin syringe. Reconstitution is simply the process of dissolving a lyophilized (freeze-dried) peptide powder into a liquid so it can be measured and injected. Add the water, and the calculator gives you the concentration in mcg/ml, the amount per 10 units and per 1 unit, and the exact draw for any target dose.
How to calculate peptide dosage
- Concentration (mcg/ml) = (vial size in mg × 1000) ÷ bacteriostatic water in ml.
- Volume for your dose (ml) = target dose in mcg ÷ concentration.
- Units to draw = volume in ml × 100 (on a standard U-100 insulin syringe).
Example: a 5 mg vial reconstituted with 2 ml of BAC water gives 2,500 mcg/ml. A 250 mcg dose is 0.1 ml, or 10 units. The peptide dose calculator above does this for you and updates live as you type.
What is bacteriostatic water?
Bacteriostatic water (BAC water) is sterile water containing 0.9% benzyl alcohol, which stops bacterial growth so a reconstituted vial stays usable for up to 28 days when refrigerated. It's the standard diluent for reconstituting peptides. More water makes a weaker solution that's easier to measure in small doses; less water makes a stronger, more concentrated solution.
Reconstitution & dosage for popular peptides
The same math applies to every compound. This tool doubles as a semaglutide reconstitution calculator, tirzepatide reconstitution calculator, and retatrutide reconstitution calculator, as well as a general peptide calculator for research peptides like BPC-157, TB-500, ipamorelin, and CJC-1295. Pick your vial size, set your water, and read the units to draw. For a blend or stack in a single vial, use the Blend / Stack tab to see the per-peptide dose.
Blend and stack dosing in one vial
Blended vials hold more than one peptide in the same powder, a 10 mg BPC-157 / TB-500 blend for example. The math is the same, but each compound owns a share of every draw. The Blend / Stack tab splits the vial by ratio and shows what each unit contains, so you know a single 20-unit draw delivers 250 mcg of BPC-157 and 250 mcg of TB-500 at the same time.
Converting mg to mcg (and back)
Peptide dosing mixes units constantly. Vials are labeled in milligrams, protocols are written in micrograms, and syringes read in units. The conversion is fixed: 1 mg = 1,000 mcg. The Converter tab handles both directions, so a 0.25 mg semaglutide dose reads as 250 mcg without mental math, and a 500 mcg BPC-157 dose reads as 0.5 mg.
Half-life and dosing frequency
A peptide's half-life is how long your body takes to clear half of it. Short half-life compounds like ipamorelin (roughly 2 hours) leave fast and are dosed daily or more often. Long half-life compounds like semaglutide (about 7 days) build toward a steady state over 4 to 5 half-lives. The Half-Life tab charts that build-up and shows how much remains between doses, which is why a weekly GLP-1 injection holds its level and a growth hormone secretagogue does not.
GLP-1 titration schedules
Semaglutide, tirzepatide, and retatrutide all start low and step up over weeks to limit nausea and GI side effects. A typical semaglutide ramp runs 0.25 mg weekly for 4 weeks, then 0.5 mg, then upward as tolerated. The Titration tab builds the week-by-week schedule for your compound and target dose, including the units to draw at every step.
Peptide calculator FAQ
It depends on concentration. With a 5 mg vial in 2 ml BAC water (2,500 mcg/ml), 250 mcg = 10 units. Enter your own numbers above for an exact figure.
There's no single right amount. 1 to 3 ml per vial is common. More water makes doses easier to measure precisely, and the calculator shows the resulting concentration for whatever volume you choose.
Generally up to 28 days refrigerated at 2 to 8 °C (36 to 46 °F) when mixed with bacteriostatic water. Never freeze a reconstituted vial, and discard if the solution is cloudy or has particles.
Yes. Toggle the dose input between mcg and mg. The calculator converts internally and always returns units and volume to draw.