Peptide reconstitution calculator
Milligrams in the vial, millilitres of water, the dose you want — and it shows how many units to draw on your syringe. Free, no sign-up, and nothing you type leaves your browser.
Watch: reconstitution, explained
The full step-by-step guide: mg, mL, units and the syringe. The video loads from YouTube only when you press play.
How the maths works
Three steps, the same ones the Dr.Peptide app uses. The worked example is the calculator's default: a 10 mg vial, 2 mL of water, a 250 mcg dose and a U-100 syringe.
1 · Concentration
Peptide ÷ water. 10 mg ÷ 2 mL = 5 mg/mL, which is 5,000 mcg in every millilitre.
2 · Volume
Dose ÷ concentration. 250 mcg is 0.25 mg; 0.25 mg ÷ 5 mg/mL = 0.05 mL.
3 · Units
Volume × syringe scale. 0.05 mL × 100 units/mL = 5 units on a U-100 syringe — or 2 units on a U-40.
Questions
What is the difference between U-100 and U-40 syringes?
The number is how many unit markings span one millilitre. On a U-100 syringe 100 units is 1 mL, so 10 units is 0.1 mL. On a U-40, 40 units is 1 mL, so 10 units is 0.25 mL. Reading one scale as the other changes the volume by a factor of 2.5 — check the label on the packet.
Why does the barrel size matter?
It sets the most you can draw at once. A 0.3 mL U-100 barrel stops at 30 units, so a 40-unit draw won't fit. The calculator flags that so you can pick a bigger barrel, change the preparation or split the draw.
Can I convert IU to mg?
Only with a factor for that specific compound. An international unit measures biological activity, not mass, so there's no single IU-to-mg conversion. The calculator asks for the factor instead of guessing one.
How much bacteriostatic water should I add?
Aim for about 10 units per dose — a 2- or 3-unit draw is hard to measure accurately on the markings. The calculator works out the water for you and offers a one-tap “Use” button. The formula: water (mL) = vial (mg) × 10 ÷ syringe scale ÷ dose (mg). A 10 mg vial and a 250 mcg dose on a U-100 syringe needs 4 mL. Follow your prescriber's or the product's instructions where they say otherwise.
What does blend mode do?
For a vial that already contains more than one compound, enter how many milligrams of each it holds, the water you added and the units you draw. It shows how much of each compound that draw contains.
Is anything I type stored or sent anywhere?
No. The maths runs in this page in your browser. There's no form submission, no account and nothing saved.