Use this calculator to work out the concentration of a reconstituted research peptide and the exact volume to draw to reach a target amount. Enter the peptide mass in the vial, the volume of bacteriostatic water added, and your target dose.
New to reconstitution? Read the full how to reconstitute peptides guide, then browse research peptides and bacteriostatic water.
Concentration: 2500 mcg/ml
Draw to reach 250 mcg: 0.100 ml (10 units on a U-100 syringe)
Reconstitution concentration is governed by a single relationship: concentration (mg/ml) equals the peptide mass in the vial (mg) divided by the volume of bacteriostatic water you add (ml). The freeze-dried peptide mass never changes — only the water volume sets how concentrated the resulting solution is. Once you know the concentration, the volume needed to reach a target amount is that target (mg) divided by the concentration (mg/ml), which the calculator converts into millilitres and unit markings for a standard insulin-style syringe.
Suppose a vial contains 10mg of peptide and you add 2ml of bacteriostatic water. The concentration is 10 ÷ 2 = 5mg/ml. To measure a 0.5mg target you would draw 0.5 ÷ 5 = 0.1ml, which is 10 units on a 100-unit (1ml) syringe. Adding 1ml of water instead would give 10mg/ml, halving the volume drawn for the same target — useful when you need finer measurements but harder to draw accurately at very small volumes.
There is no single correct water volume — it is a trade-off. Larger volumes produce a more dilute solution that is easier to measure precisely in small fractions, while smaller volumes concentrate the peptide and reduce the liquid handled. Most researchers pick a volume that keeps typical measured amounts within an easily readable range on their syringe. For the full sterile procedure, see our how to reconstitute peptides guide and the compound-specific retatrutide & tirzepatide reconstitution walkthrough.
Reconstitution arithmetic assumes the full stated peptide mass dissolves into the added water and that the powder itself adds negligible volume, which is a reasonable approximation for the small masses involved. Always verify the peptide mass against the batch Certificate of Analysis, use sterile technique, and store reconstituted solution per our storage guidelines. This tool is a calculation aid for laboratory research handling only and is not dosing or administration guidance.
Research Use Only: Not for human consumption. Strictly for in-vitro research and laboratory use.
