What is the reverse BAC calculator?

The reverse mode answers the question 'how much bacteriostatic water should I add so each dose lands on a clean tick mark?' You enter the vial size, the dose you want, and the units you'd like to draw. It tells you the exact mL of BAC water to mix in.

How do I calculate units to draw on an insulin syringe?

Concentration (mg/mL) = vial mg ÷ BAC water mL. Volume (mL) = dose (mg) ÷ concentration. Units on a U-100 syringe = volume × 100. Our calculator handles all of this and lets you pick U-100, U-50, U-40, or a 1 mL tuberculin syringe.

Which syringe should I use for peptide injections?

U-100 insulin syringes are by far the most common for subcutaneous peptide use because they read in 100 units per mL with very fine markings. U-40 and U-50 syringes are used in some veterinary or specialty contexts. Always match the syringe markings to what your calculator outputs.

Can I use this for GLP-1s like semaglutide and tirzepatide?

Yes, for compounded vial product. Brand pen products (Ozempic®, Wegovy®, Mounjaro®, Zepbound®) use a fixed concentration; for those see our GLP-1 dose escalator. For a compounded multi-dose vial of semaglutide or tirzepatide, this calculator gives you the units per dose.

How accurate is this calculator?

The math is exact for the inputs you provide. Real-world variability comes from vial overfill (most vials contain 5–15% extra solvent), syringe dead-space, and operator technique. Always verify the math yourself and consult a licensed physician.

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Peptide Reconstitution Calculator

Forward mode: how many units to draw. Reverse mode: how much bacteriostatic water to add. Works with U-100, U-50, U-40, and 1 mL syringes.

✨Prefilled for Mazdutide. View Mazdutide's profile

Reconstitution Calculator

Vial quantity

Total amount of peptide in the vial.

Bacteriostatic water added

Volume of BAC water you'll mix into the vial.

Desired dose

mcg

Syringe type

Draw to this mark

120units

= 1.2 mL on a U-100 syringe

Concentration2.5 mg/mL

Per unit25 mcg

Doses in vial1.7 doses

Syringe preview100.0 / 100 units

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Frequently asked questions

Educational use only

This calculator is provided for research and educational purposes. Outputs are derived from the values you enter. Always verify your math and consult a licensed physician before acting on any result.

Reconstitution Calculator

Frequently asked questions

What is the reverse BAC calculator?+

How do I calculate units to draw on an insulin syringe?+

Which syringe should I use for peptide injections?+

Can I use this for GLP-1s like semaglutide and tirzepatide?+

How accurate is this calculator?+

Educational use only