Peptide reconstitution calculator
By Tessaro Pty Ltd, the maker of Pepti · Reviewed
Enter what is on your vial, how much water you added, and the dose you already have. The calculator converts that into a draw volume, U-100 syringe units, and how many doses the vial holds. It works the same for BPC-157, semaglutide, tirzepatide, or any lyophilised peptide.
This free calculator works out the exact volume to draw and the U-100 syringe units for your peptide — straight from your vial size, the amount of water you mixed in, and the dose you already have.
It is a free web tool, not part of the Pepti app, and it never suggests a dose: you tell it the dose you already have, and it does the arithmetic. For the working explained step by step, read how to work out what to draw.
Fill in all three values to see your draw.
What the calculator is doing
Concentration (mg/mL) = vial strength (mg) ÷ water added (mL) Volume to draw (mL) = your dose (mg) ÷ concentration (mg/mL) Syringe units = volume (mL) × 100 (U-100 syringe) Doses per vial = water added (mL) ÷ volume per dose (mL)
Most insulin syringes sold for at-home use are U-100, marked 0 to 100 units. If your syringe is marked in units and reaches 100, the units figure applies. If it is marked in millilitres only, read the mL figure directly. The full working is on the reconstitution guide.
A worked example
Illustrative conversion only — not a dose. A 10 mg vial with 2 mL of bacteriostatic water added gives 5 mg/mL. A 0.5 mg target means 0.5 ÷ 5 = 0.1 mL. 0.1 mL × 100 = 10 units on a U-100 syringe. 2 mL of water, drawing 0.1 mL per dose, gives 20 doses.
The mistake almost everyone makes
If you change how much water you add, every unit number you had memorised is wrong. The vial has not changed — the concentration has. Run the numbers again from the top whenever your water volume changes, and write the new figure on the vial.
Common questions
How do you calculate peptide reconstitution?
Three lines. Concentration is the amount in the vial divided by the volume of water you added. The volume to draw is the figure you already have divided by that concentration. Syringe units on a U-100 syringe are the draw volume multiplied by 100. The calculator above does all three from the numbers you enter; the figure itself comes from whoever directs your use.
How many mL of bacteriostatic water do you mix with a peptide?
There is no single volume, and this page does not give one. The water sets the concentration, not the amount of peptide: more water means a lower concentration and a larger draw for the same figure. The volume is chosen with the syringe you use in mind, with whoever directs your use, and then entered here. Our page on bacteriostatic water for a 5 mg vial explains the method in full.
This tool converts values you already have. It does not recommend, suggest, or calculate any dose.
To keep the record once the arithmetic is done, the Pepti peptide tracker records your protocol, injection sites and logs, with each vial’s lot and dates; the app itself does not do this calculation. For how it fits a full routine, see the peptide tracking app guide.
Not medical advice. Pepti is a record-keeping tool, not a medical device.
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