Free tool
Peptide reconstitution calculatorVial size and bacteriostatic water into insulin-syringe units
Enter what's in the vial, how much bacteriostatic water you added, and the dose you want. You get the number of units to draw to — and the arithmetic behind it, so you can check it yourself. Nothing to download, no account, nothing sent anywhere.
That's 0.1 ml at a concentration of 2.5 mg/ml — about 20 doses per vial.
The arithmetic
5 mg ÷ 2 ml = 2.5 mg/ml0.25 mg ÷ 2.5 mg/ml = 0.1 ml0.1 ml × 100 units/ml = 10 unitsFor educational and research purposes only. This calculator does unit arithmetic on the numbers you type — it does not recommend a dose, does not know your circumstances, and is not medical advice. Consult a healthcare provider before starting any peptide regimen, and verify anything here against current medical and regulatory sources.
The method
Three divisions, in order.
Concentration
Peptide in the vial ÷ bacteriostatic water added. A 5mg vial with 2ml of water is 2.5mg per ml. This is a property of how you mixed it, not of your dose.
Volume
Target dose ÷ concentration. A 250mcg dose is 0.25mg, and 0.25mg ÷ 2.5mg/ml is 0.1ml. Watch the units here — mcg to mg is where most mistakes happen.
Syringe units
Volume × units per ml. A U-100 insulin syringe is 100 units per ml, so 0.1ml is 10 units. That is the mark you draw to.
FAQ
Straight answers.
How do I calculate peptide reconstitution?
You need three numbers: the peptide in the vial (say 5mg), the bacteriostatic water you add (say 2ml), and your target dose (say 250mcg). Divide the peptide by the water to get the concentration — 5mg ÷ 2ml = 2.5mg/ml. Divide the dose by that concentration to get the volume — 0.25mg ÷ 2.5mg/ml = 0.1ml. On a U-100 insulin syringe, 1ml is 100 units, so 0.1ml is 10 units. Ten units is what you draw to.
How much bacteriostatic water should I add to a 5mg vial?
There is no single correct amount — the water volume sets the concentration, not the dose. More water means a larger, easier-to-measure volume per dose; less water means a smaller one. 1ml to 3ml is the common range for a 5mg vial. Pick the amount that puts your usual dose at a comfortable mark on the syringe: with a 5mg vial and a 250mcg dose, 2ml puts you at 10 units, which is easy to read.
What does U-100 mean on an insulin syringe?
U-100 means the barrel is graduated for insulin at 100 units per millilitre, so 100 units = 1ml, 50 units = 0.5ml, and 10 units = 0.1ml. That conversion is a property of the syringe and holds regardless of what is in it. U-40 syringes, mostly veterinary, are 40 units per millilitre — using one by mistake gives a very different volume for the same unit count.
Does the calculator work for BPC-157, TB-500, and semaglutide?
Yes. The arithmetic is the same for any lyophilised peptide, because it only depends on the milligrams in the vial, the millilitres of water added, and your target dose. The compound name does not enter the calculation.
Is my dose too small to measure?
If the result comes out under about half a unit, there is no mark on the barrel to draw to accurately. Reconstituting the same vial with more bacteriostatic water lowers the concentration, which makes the volume for the same dose larger and measurable.
Is this medical advice?
No. This calculator performs unit arithmetic on numbers you supply. It does not recommend a dose, does not know your circumstances, and is not a substitute for a healthcare provider. It is provided for educational and research purposes only.
Want this on your phone, with your protocol attached?
Peptide Vault has the same calculator built in — free, alongside a 203-compound reference library and dose logging that stays on your device. Free to download.
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