How the peptide calculator works
Lyophilized (freeze-dried) peptides come as a powder measured in milligrams. Once a known volume of bacteriostatic water is added, the vial holds a solution with a specific concentration. From that point on, every amount of peptide corresponds to a volume of liquid, and every volume corresponds to a mark on a syringe. This peptide calculator converts between those three things.
- Enter the vial size in mg. This is the total amount printed on the vial label.
- Enter the BAC water you added in mL. The calculator divides the two to get the concentration.
- Enter the dose to convert, in mcg or mg. This comes from your own records or prescription. The calculator converts it to a draw volume and shows where that falls on a U-100 syringe.
Everything runs in your browser. Nothing you type is uploaded, there is no signup, and results update as you type.
The peptide reconstitution formula
There is no hidden logic. The whole tool is three lines of arithmetic, and the “Show the math” panel prints them with your own numbers.
1. Concentration
2. Draw volume
If the amount is in micrograms, it is divided by 1,000 first to convert it to milligrams.
3. Syringe units
A U-100 insulin syringe has 100 unit marks per millilitre, so one unit is 0.01 mL.
Worked example of the math
The numbers below are arbitrary and chosen only because they divide cleanly. They illustrate the formula and are not a suggested amount for anything.
- Vial size: 5 mg. Water added: 2 mL.
- Concentration: 5 ÷ 2 = 2.5 mg/mL (2,500 mcg/mL, or 25 mcg per unit mark).
- Amount entered: 250 mcg, which is 250 ÷ 1,000 = 0.25 mg.
- Volume: 0.25 ÷ 2.5 = 0.1 mL.
- Syringe units: 0.1 × 100 = 10 units on a U-100 syringe.
Press “Try example numbers” in the calculator above to see the same values on the syringe illustration.
Insulin syringe types: U-100, U-50 and U-40
The “U” number describes how a syringe’s scale is printed. Reading a result against the wrong scale changes the volume, so it is worth knowing which one is in your hand.
| Syringe | Marks per mL | 1 unit equals | Typical barrels |
|---|---|---|---|
| U-100 | 100 units | 0.01 mL | 0.3 mL (30 units), 0.5 mL (50 units), 1 mL (100 units) |
| “U-50” | 100 units | 0.01 mL | Common shorthand for the 0.5 mL, 50-unit U-100 syringe |
| U-40 | 40 units | 0.025 mL | 1 mL (40 units), mostly veterinary |
U-100 is the standard insulin syringe and the scale this calculator displays. The 0.3 mL, 0.5 mL and 1 mL versions all use the same unit size. A smaller barrel simply spreads the marks further apart, which makes small volumes easier to read.
“U-50” is usually shorthand for a 0.5 mL U-100 syringe that holds 50 units. Its unit marks mean exactly the same volume as on any other U-100 syringe, so you can select “0.5 mL” in the calculator.
U-40 syringes are genuinely different. They have only 40 marks per mL, so one U-40 unit is 0.025 mL, which is 2.5 times the volume of a U-100 unit. To express a volume on a U-40 scale, multiply the mL figure by 40 instead of 100. Always check the scale printed on the barrel.
Unit conversions: mcg, mg and mL
- 1 mg = 1,000 mcg. 0.5 mg is 500 mcg, and 250 mcg is 0.25 mg.
- 1 mL = 100 units on a U-100 syringe. 0.1 mL is 10 units, and 0.05 mL is 5 units.
- mg and mL are not interchangeable. Milligrams measure an amount of powder. Millilitres measure a volume of liquid. The concentration is what links them.
- Syringe units are not IU. The International Units on some product labels measure biological activity and are specific to each substance. They cannot be converted here.
Common arithmetic slips this helps you catch
- mcg entered as mg. This shifts the result by 1,000×. The calculator flags any amount larger than the whole vial.
- Units read as mL. 10 units is 0.1 mL, not 10 mL. Both figures are shown side by side.
- The wrong syringe scale. A result in U-100 units does not apply to a U-40 barrel.
- Reusing an old concentration. A new vial size or a different water volume means a new concentration. Recalculate for each vial.
- A volume too large for the barrel. The calculator tells you when a result exceeds the syringe size you selected.
Want the concentration stored with each vial so you never retype it? The free Peptrack app saves it alongside your vial inventory and dose log.
What this calculator does not do
This is a math tool, and it is important to be clear about where it stops.
- It does not recommend, suggest or verify any dose, schedule or protocol.
- It does not know what is in your vial, and it has no information about you.
- It does not decide how much water to add. If the instructions from your pharmacy, manufacturer or healthcare provider give a volume, use that one. To see how different volumes would read on a syringe, compare them in the BAC water calculator.
- It does not provide medical advice, diagnosis or treatment.
Results are for research, informational and record-keeping reference only. Always confirm measurements with a licensed healthcare provider or pharmacist. See the full disclaimer.
Looking for a different angle on the same math? Try the reconstitution calculator, the BAC water calculator or the peptide dosage calculator, or head back to the Peptrack homepage.
