Peptide Calculator

The reverse reconstitution calculator. Enter your vial size and target dose — we'll tell you exactly how much bacteriostatic water to add and where to draw on your syringe.

Quick Start — Peptide Presets

Select a peptide to auto-fill common vial sizes and doses.

Reverse Reconstitution Calculator

Enter your vial size and target dose — we'll tell you exactly how much water to add and where to draw.

mg
$

Add BAC water

1.00mL

Draw to mark

5units

Concentration

5000mcg/mL

Doses per vial

20doses

0.5 mL Syringe (U-100)

010203040505u

5 units

(0.050 mL)

Disclaimer: This calculator is for educational purposes only. Always consult a qualified healthcare professional before reconstituting or administering any peptide. Verify all calculations independently. PepStack is not responsible for dosing decisions.

PepStack is for research and educational purposes only. This is not medical advice. Always consult a qualified healthcare provider before using any peptides. Dosing data is sourced from published research and community protocols — verify with your provider.

How the Reverse Reconstitution Calculator Works

Most peptide calculators ask the wrong question: “How much water did you add?” But if you haven't reconstituted yet, that's not helpful. You know your vial size and your target dose — you need to know how much water to add so that your dose is easy and accurate to draw.

The Problem with Odd Syringe Volumes

If you randomly add 2 mL to a 5 mg vial and need 250 mcg, the math says draw 5 units — clean. But add 1.5 mL and you get 3.33 units, which doesn't exist on any syringe. Our calculator finds the water volume that makes your dose land on a real tick mark.

Tick-Mark Snapping

Real insulin syringes have graduations at every 1 or 2 units depending on the size. A 0.5 mL syringe has marks at every 1 unit. A 1 mL syringe has marks at every 2 units. The calculator considers your syringe type and snaps to the closest real mark, then back-calculates the optimal water volume.

Choosing the Right Syringe

Smaller syringes are more accurate for small doses. If your dose is under 30 units, use a 0.3 mL syringe. Under 50 units, use a 0.5 mL. Only use a 1 mL syringe for larger doses. The visual syringe guide shows exactly where to draw for your calculated dose.

Common Peptide Reconstitution Examples

  • BPC-157 (5 mg vial, 250 mcg dose): Add 2 mL BAC water, draw 5 units on a 0.5 mL syringe. 20 doses per vial.
  • Semaglutide (5 mg vial, 0.25 mg dose): Add 2.5 mL BAC water, draw 5 units. 20 doses per vial.
  • Tirzepatide (10 mg vial, 2.5 mg dose): Add 2 mL BAC water, draw 10 units on a 0.5 mL syringe. 4 doses per vial.
  • Sermorelin (5 mg vial, 200 mcg dose): Add 2.5 mL BAC water, draw 10 units. 25 doses per vial.

Storing Reconstituted Peptides

After mixing, refrigerate at 2–8°C (36–46°F). Most peptides stay stable 3–4 weeks. Never freeze reconstituted solutions, and always use alcohol swabs and sterile technique when drawing doses.