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Peptide Calculator: mg/mL, mL and U-100 Units
By Baris Bingor · Last updated
How do I calculate how many units to draw?
Divide the vial's mass by the water you add to get mg/mL, divide the amount by that to get mL, and multiply by 100 for units on a U-100 syringe. A 5 mg vial with 2 mL of bacteriostatic water is 2.5 mg/mL, so 250 mcg is 0.1 mL, or 10 units. The calculator below does it for any numbers you type.
Reconstitution calculator
Type your own numbers. They aren't sent anywhere: the math runs in your browser.
Type an amount to see the volume and the units.
Arithmetic only. Peptly does not suggest amounts: the amount is yours, from your protocol or the product's documentation. Not medical advice.
The formula
- Concentration (mg/mL) = peptide in the vial (mg) ÷ water added (mL).
- Volume to draw (mL) = amount (mg) ÷ concentration (mg/mL). 1 mg = 1,000 mcg.
- U-100 units = volume (mL) × 100. On a U-100 insulin syringe, 1 unit = 0.01 mL and 100 units = 1 mL.
Worked examples
- 5 mg vial, 2 mL water, 250 mcg: 5 mg ÷ 2 mL = 2.5 mg/mL. 250 mcg (0.25 mg) ÷ 2.5 mg/mL = 0.1 mL. 0.1 mL × 100 = 10 units on a U-100 syringe.
- 10 mg vial, 2 mL water, 500 mcg: 10 mg ÷ 2 mL = 5 mg/mL. 500 mcg (0.5 mg) ÷ 5 mg/mL = 0.1 mL. 0.1 mL × 100 = 10 units on a U-100 syringe.
- 5 mg vial, 3 mL water, 1 mg: 5 mg ÷ 3 mL = 1.667 mg/mL. 1 mg ÷ 1.667 mg/mL = 0.6 mL. 0.6 mL × 100 = 60 units on a U-100 syringe.
- 2 mg vial, 1 mL water, 100 mcg: 2 mg ÷ 1 mL = 2 mg/mL. 100 mcg (0.1 mg) ÷ 2 mg/mL = 0.05 mL. 0.05 mL × 100 = 5 units on a U-100 syringe.
| Water | mg/mL | 100 mcg | 250 mcg | 500 mcg | 1 mg | 2 mg |
|---|---|---|---|---|---|---|
| 1 mL | 5 | 2 | 5 | 10 | 20 | 40 |
| 2 mL | 2.5 | 4 | 10 | 20 | 40 | 80 |
| 3 mL | 1.667 | 6 | 15 | 30 | 60 | 120† |
| 5 mL | 1 | 10 | 25 | 50 | 100 | 200† |
| Water | mg/mL | 100 mcg | 250 mcg | 500 mcg | 1 mg | 2 mg |
|---|---|---|---|---|---|---|
| 1 mL | 10 | 1 | 2.5 | 5 | 10 | 20 |
| 2 mL | 5 | 2 | 5 | 10 | 20 | 40 |
| 3 mL | 3.333 | 3 | 7.5 | 15 | 30 | 60 |
| 5 mL | 2 | 5 | 12.5 | 25 | 50 | 100 |
Each cell is units on a U-100 syringe: amount ÷ (vial mg ÷ water mL) × 100. † More than one full 1 mL (100-unit) syringe. The amounts are columns of arithmetic, not suggestions; the amount is yours, from your protocol or the product's documentation. Not medical advice.
Keeping a log: the Peptly app
The calculator lives on this website. The Peptly app for iPhone and iPad is a separate tool, a private log: it keeps what you enter and never works out, converts or suggests an amount.
- Entries exactly as you type them — the amount, the site and a note, shown as you entered them.
- Today, with Log and Skip — see what is planned and mark each entry in one tap.
- Reminders on your own schedule — one is free; Peptly Pro adds unlimited reminders.
- Injection-site rotation — Peptly suggests the site you used longest ago, other than the last one.
- 23 peptides in the library, plus your own — plain-language profiles with no amounts, frequencies or regimens.
- Your log stays on your phone — no accounts, no cloud sync.
For per-peptide references see
- BPC-157 reconstitution math
- TB-500 reconstitution math
- Semaglutide reconstitution math
- Tirzepatide reconstitution math
- Ipamorelin reconstitution math
- BAC water calculator
- How to reconstitute peptides: step-by-step
Frequently asked questions
Is the Peptly peptide calculator free? +
Yes. The calculator on this page is free, runs in your browser and needs no account. It is a web tool only: the Peptly app for iPhone and iPad is a log and does not do this math.
What does the calculator actually compute? +
Given a vial mass (e.g. 5 mg), a bacteriostatic water volume (e.g. 2 ml), and a target dose (e.g. 250 mcg), it computes the concentration (2.5 mg/ml) and the exact units to draw on a U-100 insulin syringe (10 units). It also shows the draw mark on a visual syringe.
What does the Peptly app do? +
The Peptly app for iPhone and iPad is a private log and tracker, not a calculator. You log each entry with the amount you type, shown exactly as you typed it; Today shows what is planned, with Log and Skip; reminders follow your own schedules; and it suggests the injection site you used longest ago, other than the last one. Its library describes 23 peptides in plain language, with no amounts. No account; your log stays on your phone.
Does it work for semaglutide and tirzepatide? +
Yes. The calculator is arithmetic, so it works for semaglutide, tirzepatide, retatrutide and any other peptide in a vial: type the vial mass, the water added and the amount. The math is identical to research peptides; only the typical dose mass is different.
Which syringe scale does the calculator use? +
U-100, the most common in research: 100 units = 1 mL, so 1 unit = 0.01 mL. It also shows the volume in mL, which you can read on any scale.