Peptide calculator: dosage and reconstitution

Work out the concentration, then the volume, then the units. Concentration in mcg per mL is the vial mass in mg × 1,000 ÷ the millilitres of water added. Volume is your dose in mcg ÷ that concentration. On a U-100 syringe, units = millilitres × 100. Example: a 5 mg vial with 2 mL of bacteriostatic water is 2,500 mcg per mL, so 250 mcg is 0.1 mL, which is 10 units. The calculator above does all three steps and shows the fill on the syringe.

There is no single correct amount - the water volume is a measuring choice, not part of the dose. More water lowers the concentration, so the same dose takes up more units on the syringe. For a 250 mcg dose from a 5 mg vial: 1 mL of water makes it 5 units, 2 mL makes it 10 units, 3 mL makes it 15 units. More units are easier to measure accurately, but the draw has to fit in your syringe barrel. The number of doses in the vial is the same whichever you choose.

U-100 means 100 units per millilitre, so 1 unit is 0.01 mL and 10 units is 0.1 mL. Almost all insulin syringes are U-100. The 0.3 mL, 0.5 mL and 1 mL barrels hold 30, 50 and 100 units - those are capacities, and every one of them is still marked at 100 units per mL.

Divide the peptide in the vial by the dose, in the same unit. A 5 mg vial is 5,000 mcg, so at 250 mcg per dose it holds 20 doses; a 10 mg vial at 500 mcg per dose also holds 20. The water you add does not change this - it changes only how much volume each dose takes up.

Multiply by 1,000: 1 mg is 1,000 mcg, so a 5 mg vial holds 5,000 mcg and a 0.25 mg dose is 250 mcg. Vials are usually labelled in mg and research-compound doses are usually quoted in mcg, which is why a slip between the two is a 1,000× error. The calculator takes the vial in mg and the dose in mcg so the conversion is done for you.

There is no such thing as a U-50 syringe scale. The U-number means units per millilitre, so U-100 is 100 units per mL. What people call a "U-50" is a 0.5 mL syringe that holds 50 units - and it is still marked at 100 units per mL. Insulin syringes are sold in 0.3 mL, 0.5 mL and 1 mL barrels, and essentially all of them are U-100. If a calculator treats U-50 as 50 units per mL it will tell you to draw half the volume you intended.

No. The number of doses in a vial depends only on how much peptide is in it and how large each dose is. Adding more water dilutes the solution, so you draw a larger volume for the same dose - the dose count is unchanged. More water can still be useful: it spreads a small dose across more syringe units, which makes it easier to measure accurately.

Multiply by the syringe scale. On a U-100 syringe, units = millilitres × 100, so 0.1 mL is 10 units. On a U-40 syringe, units = millilitres × 40, so 0.1 mL is 4 units. The barrel size does not affect this conversion - it only limits how much fits in one draw.

Sterile water containing benzyl alcohol as a preservative, which allows a vial to be entered more than once. It is typically 0.9% benzyl alcohol, though 1.1% products also exist. It is labelled not for use in neonates. It is not the same as sterile water for injection, which contains no preservative.

No. It performs arithmetic on numbers you enter - concentration, volume, and syringe units. It does not know what compound you have, whether any dose is appropriate for you, or whether you should be using it at all. Many compounds discussed on this site are sold for laboratory research use only and are not approved for human use.

All three. A peptide dosage, dosing, mixing or reconstitution calculator is the same arithmetic under different names. This tool covers concentration after mixing, the volume to draw for a dose, syringe units and doses per vial. The peptide reconstitution calculator at /peptide-reconstitution-calculator/ runs the same tool with a guide to choosing a water volume, and the calculators for specific peptides on this page open it with an example vial preloaded.

It will do unit conversion on any numbers you type, and there are dedicated tirzepatide, semaglutide and retatrutide calculator pages below. For prescription GLP-1 medicines, follow the labelled product and your prescriber. FDA has warned about unapproved GLP-1 products and dosing errors.