Peptide Calculator

How much diluent should you add?

There is no single correct volume. The diluent (for example, bacteriostatic water) does not change how much peptide is in the vial; it only sets the concentration of the solution. A larger diluent volume gives a lower concentration, so each aliquot needs a larger pipette volume, which is easier to measure precisely. A smaller diluent volume gives a more concentrated solution and smaller pipette volumes, where small measuring errors matter more.

A practical approach is to choose the diluent volume that puts your target aliquot mass at a pipette volume your equipment measures accurately. The “Compare diluent volumes” table in the result panel shows 0.5 to 3 mL side by side.

The formulas

1. Concentration (mg/mL) = vial mass (mg) ÷ diluent volume (mL)
2. Pipette volume (mL) = target aliquot mass (mg) ÷ concentration (mg/mL)
3. Pipette volume (µL) = pipette volume (mL) × 1,000
4. Full aliquots per vial = vial mass (mg) ÷ target aliquot mass (mg)

1 mg equals 1,000 mcg, so divide mcg by 1,000 before using the formulas. The calculator assumes the diluent volume equals the final solution volume; the dissolved solid adds a small volume that it ignores.

Worked example

A 10 mg vial reconstituted with 2 mL of diluent gives 10 ÷ 2 = 5 mg/mL. A 1 mg aliquot needs 1 ÷ 5 = 0.2 mL, which is 200 µL. The vial yields 10 ÷ 1 = 10 aliquots of that mass.

Quick reference: peptide mass in 100 µL

This table shows how much peptide 100 µL (0.1 mL) of solution contains for common vial masses and diluent volumes.

Materials

Reconstitution Solution comes as a box of two 10 mL vials. For peptide formats and lot reports, see Retatrutide vials (10–50 mg) or the full catalog. For storing sealed vials, read the peptide storage guide.