Reconstituting a peptide sounds more complicated than it is. Once you understand three numbers — how much is on the vial, how much liquid you added, and how much you want to measure — the rest is just division.
The three numbers that matter
1. Vial amount. This is the total quantity printed on the vial label, usually in milligrams (mg) or micrograms (mcg).
2. Liquid added. This is how much bacteriostatic water (or other diluent) you mixed into the vial, measured in milliliters (mL). This is the number that determines concentration — the same vial mixed with more liquid becomes less concentrated, and vice versa.
3. Amount to measure. This is the amount you want the syringe to contain, and it’s what the calculator converts into a liquid volume and a syringe mark.
The formula
Concentration is simply the vial amount divided by the liquid volume:
vial amount ÷ liquid added = concentration (mg/mL)
Once you know the concentration, converting an amount you want to measure into a liquid volume is another division: your target amount divided by the concentration.
Why syringes complicate things
Most reconstitution math gets confusing not because the arithmetic is hard, but because vials are labeled in mg while syringes are marked in units — and the two don’t automatically line up. A standard insulin-style syringe uses a 1 mL, 100-unit scale, meaning 1 mL of liquid equals 100 units on the barrel. Once you’ve calculated the liquid volume you need, multiplying by 100 gives you the unit mark to draw to.
Try it yourself
Rather than doing this by hand, our peptide reconstitution calculator handles all three steps at once — enter your numbers and it shows the concentration, liquid volume, and syringe mark together, with the formula visible so you can check it.