Peptide Calculator

Reconstitution Calculator

The Formulas

All reconstitution maths reduces to three relationships. Once concentration is known, everything else follows from it.

The single most common source of confusion is that concentration is not a property of the peptide — it is a property of how much solvent was added. The same vial reconstituted with 1 mL or 3 mL produces concentrations that differ threefold, and every downstream number changes with it.

Worked Example

Take a 5 mg vial reconstituted with 2 mL of bacteriostatic water, and suppose you want to express 250 mcg as a volume.

1. Concentration: 5 mg ÷ 2 mL = 2.5 mg/mL, which is 2,500 mcg/mL.
2. Volume: 250 mcg ÷ 2,500 mcg/mL = 0.1 mL.
3. Syringe units: 0.1 mL × 100 = 10 units on a U-100 syringe.
4. Vial content: 5 mg = 5,000 mcg, so the vial holds 20 such amounts.

Now change one input. Reconstitute the same 5 mg vial with 1 mL instead: concentration becomes 5,000 mcg/mL, the same 250 mcg occupies 0.05 mL, and it reads as 5 units rather than 10. The peptide amount is identical; only the arithmetic changed.

Insulin Syringe Units

Insulin syringes are graduated in units rather than millilitres, which is why unit conversion causes errors. A U-100 syringe is calibrated so that 100 units corresponds to 1 mL — the marking derives from insulin at 100 units per mL, not from any property of peptides.

So 100 units = 1 mL, 50 units = 0.5 mL, 10 units = 0.1 mL. U-40 and U-50 syringes use different calibrations and are not interchangeable with U-100 markings. Reading a volume off the wrong syringe scale is a straightforward way to be off by a factor of two or more.

Important Context

This calculator answers an arithmetic question, not a research or medical one. It cannot tell you whether a given amount is supported by evidence for any compound, and it has no knowledge of what you enter.

For most research peptides there is no established human protocol at all. Amounts reported in the literature come from specific study models, routes, and durations, and do not transfer across compounds or to human use. Peptidelogy presents dosage strictly as literature context — see peptide side effects and safety for how evidence quality varies by compound, and what are peptides for background.

Concentration accuracy also assumes the vial contains what its label states. Material outside regulated supply chains may vary in identity, purity, and actual content, in which case the arithmetic is precise but the inputs are not.

Frequently Asked Questions

What does a peptide calculator do?

It converts between mass, volume, and concentration. Given the amount of peptide in a vial and the volume of solvent added, it computes the resulting concentration, then expresses a chosen amount as a liquid volume and as units on a U-100 insulin syringe. It is unit arithmetic, not a dosing recommendation.

How do you calculate peptide reconstitution?

Concentration equals the peptide mass in the vial divided by the volume of solvent added. For a 5 mg vial reconstituted with 2 mL, the concentration is 2.5 mg/mL, or 2,500 mcg/mL. To express a given amount as a volume, divide that amount by the concentration.

How many units is 250 mcg on an insulin syringe?

It depends entirely on the concentration. A U-100 insulin syringe is marked so that 100 units equals 1 mL. At 2,500 mcg/mL, 250 mcg occupies 0.1 mL, which reads as 10 units. Change the solvent volume and the same 250 mcg reads as a different number of units.

What is bacteriostatic water used for in reconstitution?

Bacteriostatic water is sterile water containing a preservative, typically 0.9% benzyl alcohol, which inhibits bacterial growth and so allows multi-use over a period. Sterile water without preservative is used in single-use contexts. Which is appropriate depends on the material and setting, and this page does not advise on that choice.

Does the calculator tell me how much to take?

No. It has no view on whether any amount is appropriate. Reported amounts in research literature vary by compound, model, route, and study design, and most research peptides have no established human protocol. Peptidelogy presents dosage strictly as literature context.