Peptide calculator.
A peptide reconstitution and dosage calculator for research vials. Enter the mg in the vial, the bacteriostatic water you add, and any amount — it returns the concentration in mg/mL and the volume in U-100 syringe units. Arithmetic only: it never suggests how much to use.
Peptide calculator
U-100 SCALE · 100 UNITS = 1 MLHow to calculate peptide concentration.
3 STEPSReconstitution and dosage math is one division and one multiplication from the mg of material, the mL of diluent and the amount you draw:
- Concentration (mg/mL) = peptide mg in vial ÷ bacteriostatic water mL
- Volume (mL) = amount in mg ÷ concentration
- Syringe units = volume × 100, since 1 unit on a U-100 scale = 0.01 mL
The markings on a U-100 syringe are units of volume, not IU. International units (IU) measure biological activity and do not convert to mL without a substance-specific factor, so they are not used here. The calculator accepts amounts in mg or mcg.
A worked example.
A 5 mg vial reconstituted with 2 mL of diluent gives a concentration of 2.5 mg/mL. An amount of 0.5 mg is then 0.5 ÷ 2.5 = 0.2 mL, which is 20 units on a U-100 scale, and the vial holds 5 ÷ 0.5 = 10 portions of that size. The figures are an arithmetic example only.
Peptide dosage: converting mg to syringe units.
To turn a dosage in mg or mcg into a draw, divide it by the reconstituted concentration for the volume in mL, then multiply by 100 for U-100 units. The same 0.5 mg amount is a different number of units at every concentration, so a dosage calculation is only valid for one reconstitution. This page converts an amount you enter; it does not set the amount.
Converting syringe units back to mg.
A U-100 insulin syringe holds 100 units in 1 mL, so 1 unit = 0.01 mL. Converting units to mg requires the reconstituted concentration. A 10-unit draw from a 5 mg vial reconstituted in 1 mL of BAC water (5 mg/mL) holds 0.5 mg; the same 10 units from a 2.5 mg/mL vial holds 0.25 mg. Recalculate whenever the reconstitution volume changes: units alone say nothing about mass.
How much bacteriostatic water to add.
Bacteriostatic water contains 0.9% benzyl alcohol as a preservative, which prevents bacterial growth across multiple draws from the same vial. Sterile (non-bacteriostatic) water is single-use and not appropriate for repeated draws from one vial. More diluent lowers the concentration and makes each draw larger and easier to measure; enter the volume above to see the resulting mg/mL.
Storage after reconstitution.
Most peptides are stable for 14–30 days at refrigerator temperature (2–8°C) post-reconstitution, protected from light. Longer storage requires freezing in single-use aliquots to avoid freeze-thaw cycles. Compound-specific stability data varies — see our reconstitution guide for detail.
Common questions.
FAQHow does a peptide calculator work?
A peptide calculator turns three numbers into a draw volume: the mg of peptide in the vial, the mL of bacteriostatic water added, and the amount you want to draw. It divides mg by mL for the concentration, divides your amount by that concentration for the volume in mL, then multiplies by 100 for U-100 syringe units. It is arithmetic; it does not decide the amount for you.
How do I calculate peptide concentration in mg/mL?
Divide the mg of peptide in the vial by the mL of bacteriostatic water you reconstitute it with. A 5 mg vial in 2 mL of water is 2.5 mg/mL.
How many units is a dose on a U-100 syringe?
Divide the amount by the concentration to get the volume in mL, then multiply by 100. On a U-100 scale 1 unit = 0.01 mL, so 0.2 mL is 20 units. Units measure volume, not mass, so recalculate whenever the reconstitution volume changes.
How much bacteriostatic water should a vial be reconstituted with?
Any volume works arithmetically; more water gives a lower concentration and a larger, easier-to-measure draw. Enter the mg and the water volume above to see the resulting mg/mL. Bacteriostatic water carries 0.9% benzyl alcohol and suits multi-draw vials; sterile water is single-use.
What is the difference between mg and mcg in the calculator?
1 mg = 1000 mcg. The calculator accepts either and converts mcg to mg before working out the volume, so the result is the same whichever unit you enter.