Peptide Reconstitution Calculator
Convert any peptide dose to insulin-syringe units in one tap. Works for tirzepatide, semaglutide, retatrutide, BPC-157, CJC-1295, ipamorelin and any custom vial.
How reconstitution math works
Reconstitution turns a lyophilised (freeze-dried) peptide vial into an injectable solution. You add bacteriostatic water (BAC water) to the vial, which gives you a concentration in mg per mL. Your dose in mg divided by that concentration gives the volume to draw. On a U-100 insulin syringe, 1 mL equals 100 units, so units = (dose mg ÷ concentration mg/mL) × 100.
Choosing a BAC water volume
More diluent means easier-to-read draw lines but a larger injection volume. A 5 mg vial reconstituted with 2 mL gives 2.5 mg/mL, so a 0.5 mg dose is 20 units. The same vial with 1 mL gives 5 mg/mL and the same dose becomes 10 units. Pick a volume that puts your typical dose between 10 and 50 units on the syringe you own.
Syringe sizes: 0.3, 0.5 and 1.0 mL
A 0.3 mL (30-unit) syringe has the finest gradations and is best for small subcutaneous doses. A 0.5 mL (50-unit) syringe suits most GLP-1 and healing-peptide protocols. The 1.0 mL (100-unit) syringe is only needed for large volumes. The calculator previews the exact draw line on all three so you can confirm before you inject.
Common reconstitution mistakes
Injecting BAC water directly onto the powder instead of running it down the vial wall can denature the peptide. Shaking instead of gently swirling causes foaming and peptide loss. Reusing a vial past its stability window (typically 28–30 days refrigerated after reconstitution) reduces potency. Always label the vial with the reconstitution date and concentration.
Frequently asked questions
How do I convert mg to insulin units?
Divide your dose in mg by the vial concentration in mg/mL, then multiply by 100. Example: a 0.25 mg dose from a 2.5 mg/mL vial is 0.1 mL, which is 10 units on a U-100 syringe.
How much bacteriostatic water should I add?
Any volume works mathematically — choose the one that puts your usual dose between 10 and 50 units on your syringe. 1 mL and 2 mL are the most common choices for 5 mg and 10 mg vials.
Is the peptide calculator free?
Yes. The reconstitution calculator, dose tracker and peptide library are free, work in the browser, and need no account.
How long does a reconstituted vial last?
Most peptides stay stable roughly 28–30 days refrigerated at 2–8 °C after reconstitution with bacteriostatic water. Sterile water shortens that window considerably.