Tool
Peptide reconstitution calculator
Also called a peptide dosage, dosing, or mixing calculator. Enter vial mass, diluent, and dose - get concentration, draw volume, and syringe units. Arithmetic only.
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Your vial
Printed on the vial. There is no standard size - enter what yours says.
This changes how much you draw - never how many doses the vial holds.
100 units per mL. 1 unit = 0.01 mL. This is what almost every insulin syringe sold is, in every barrel size.
Capacity only. A 1 mL U-100 syringe holds 100 units - the scale decides that, not the barrel.
Draw this much
= 0.1 mL on a 1 mL U-100 syringe
- Concentration
- 2,500 mcg/mL
- Exact volume
- 0.1 mL
- Dose you actually get
- 250 mcg
- Doses per vial(unaffected by water volume)
- 20
Results update in the address bar, so you can copy the link to save or share a calculation. Nothing is stored, and there is no account.
How the maths works
Reconstitution is one division and one multiplication. The whole thing is worth understanding, because a calculator you don't understand is a calculator you can't sanity-check.
1. Concentration
Divide the peptide mass by the water you added. A 5 mg vial with 2 mL of bacteriostatic water gives 2.5 mg per mL. Because doses are usually quoted in micrograms, it is easier to think in mcg: 5 mg is 5,000 mcg, so that vial is 2,500 mcg per mL.
2. Volume to draw
Divide the dose you want by the concentration. For 250 mcg from a 2,500 mcg/mL solution: 250 ÷ 2,500 = 0.1 mL.
3. Units on the syringe
This is where people come unstuck. Insulin syringes are not marked in millilitres, they are marked inunits - and the U-number tells you how many units fit in a millilitre. A U-100 syringe has 100 units per mL, so multiply millilitres by 100. That 0.1 mL is 10 units.
4. Doses per vial
Divide the total peptide by the dose size. Note what is not in that sentence: the water. A 5 mg vial at 250 mcg per dose contains 20 doses whether you reconstitute it with 1 mL or 5 mL. Water changes the volume you draw, never the number of doses. Any tool implying otherwise is wrong about arithmetic.
Common questions
What is a U-50 syringe?
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.
Does adding more bacteriostatic water make a vial last longer?
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.
How do I convert millilitres to units on an insulin syringe?
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.
What is bacteriostatic water?
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.
Is this calculator medical advice?
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.
Is this a peptide dosage calculator and mixing calculator too?
Yes. Dosage, dosing, mixing, and reconstitution calculators are the same arithmetic under different search names. This tool covers concentration after mixing, draw volume for a dose, and syringe units.
Can I use this for tirzepatide or other GLP-1 products?
It will do unit conversion on any numbers you type. For prescription GLP-1 medicines, follow the labelled product and your prescriber. FDA has warned about unapproved GLP-1 products and dosing errors.