# The Complete Peptide Reconstitution Calculator Guide

Source: https://www.trackpep.com/blog/peptide-reconstitution-calculator-guide

> Educational information only. Not medical advice, and not a dosing recommendation. TrackPep records what you enter and converts a dose you were prescribed into a syringe reading; it never decides a dose for you. Talk to a licensed clinician.

How to convert mg per vial and BAC water to syringe units, with worked examples for semaglutide and tirzepatide. Educational — not medical advice.

<Disclaimer />

If you've ever stared at a vial of lyophilized peptide and wondered how a number on a syringe maps back to milligrams, you're in the right place. This guide walks through every step, with worked examples for the most common GLP-1s and research peptides.

## What is reconstitution?

Reconstitution is the process of mixing a freeze-dried peptide with **bacteriostatic water (BAC water)** to produce an injectable solution at a known concentration. The peptide arrives dry; you add water; you draw a known volume; that volume contains a known dose. Simple in concept — easy to mis-math in practice.

## The only equation you need

**Concentration (mg/mL) = mg per vial ÷ mL of BAC water**

That's it. Everything else flows from this.

Once you know your concentration, picking a dose is just division:

**Dose volume (mL) = target dose (mg) ÷ concentration (mg/mL)**

And to map volume to syringe units:

- **U-100 syringe:** 1 mL = 100 units → multiply mL by 100
- **U-40 syringe:** 1 mL = 40 units → multiply mL by 40

## Worked example: semaglutide 5 mg vial, 2 mL BAC water

1. **Concentration** = 5 mg ÷ 2 mL = **2.5 mg/mL**
2. Target dose **0.25 mg**:
   - Volume = 0.25 ÷ 2.5 = **0.10 mL**
   - On a U-100 syringe = 0.10 × 100 = **10 units**
3. Target dose **0.50 mg**:
   - Volume = 0.50 ÷ 2.5 = **0.20 mL**
   - On a U-100 syringe = **20 units**

## Worked example: tirzepatide 10 mg vial, 1 mL BAC water

1. **Concentration** = 10 mg ÷ 1 mL = **10 mg/mL**
2. Target dose **2.5 mg** → 25 units U-100
3. Target dose **5 mg** → 50 units U-100

## Worked example: BPC-157 5 mg vial, 5 mL BAC water

1. **Concentration** = 1 mg/mL
2. Target dose **250 mcg (0.25 mg)** → 25 units U-100

<Callout>
mg = milligrams, mcg = micrograms (1000 mcg = 1 mg). Always convert to the same unit before dividing.
</Callout>

## Picking BAC water volume

Aim for a concentration where your typical dose lands between **10 and 50 units** on a U-100 syringe.

## U-100 vs U-40 syringes

Both are calibrated to milliliters underneath — the difference is the **scale on the barrel**. The TrackPep calculator takes the syringe type as an explicit input so it computes the right unit reading every time.

<Callout>
Always double-check the syringe scale before drawing. Reading a U-100 scale as if it were U-40 is one of the most common dosing errors.
</Callout>

## FAQ

<FAQ>
  <div>
    <dt>**Can I use regular sterile water?**</dt>
    <dd>Sterile water has no preservatives. Fine for single-use; multi-use vials require bacteriostatic water.</dd>
  </div>
  <div>
    <dt>**Does BAC water volume affect dose math?**</dt>
    <dd>No. The peptide mass doesn't change when you add water — only the concentration.</dd>
  </div>
</FAQ>

## Skip the math entirely

[The free TrackPep reconstitution calculator](/tools/reconstitution-calculator) does all of this in your browser, no signup.

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*Informational only. Always consult a licensed healthcare professional.*