# How to Reconstitute Peptides: The Math

Reconstituting a peptide means dissolving the powder in a measured volume of liquid, usually bacteriostatic water. The math is one division: amount in the vial ÷ liquid added gives the concentration, and every volume follows from it.

Canonical: https://bestpeptidecalculator.app/guides/how-to-reconstitute-peptides
Last reviewed: 2026-11-08

## What reconstitution means

Lyophilized (freeze-dried) peptides come as powder. Adding a known volume of liquid turns them into a solution with a known concentration, so an amount can be measured as a volume.

The liquid doesn’t change the amount in the vial: a 10 mg vial holds 10 mg whether you add 1 mL or 5 mL.

## The math

`concentration = amount in the vial ÷ liquid added`

`volume = amount you choose ÷ concentration`

`U-100 units = volume (mL) × 100`

## Worked examples

| Vial | Liquid | Concentration | Amount | Volume | U-100 units |
| --- | --- | --- | --- | --- | --- |
| 5 mg | 2 mL | 2.5 mg/mL | 250 mcg | 0.10 mL | 10 |
| 10 mg | 2 mL | 5 mg/mL | 500 mcg | 0.10 mL | 10 |
| 10 mg | 3 mL | 3.333 mg/mL | 500 mcg | 0.15 mL | 15 |
| 2 mg | 1 mL | 2 mg/mL | 100 mcg | 0.05 mL | 5 |

Put any row into the [reconstitution calculator](https://bestpeptidecalculator.app/reconstitution-calculator) to see the same numbers and the nearest syringe marking.

## Choosing the liquid volume

The volume is a measuring choice. More liquid means each amount takes more volume, which is easier to read on a syringe but needs more liquid per portion. Less liquid concentrates it. There is a full explanation in [how much bacteriostatic water to add](https://bestpeptidecalculator.app/guides/how-much-bac-water).

## Handling and storage

> This guide covers the arithmetic only. For handling, sterile technique and storage, follow the product’s own documentation and your research protocol.

## Frequently asked questions

### What does it mean to reconstitute a peptide?

To dissolve its powder in a measured volume of liquid, giving a solution with a known concentration.

### How do you calculate peptide reconstitution?

Divide the vial amount by the liquid volume for the concentration, then divide your amount by the concentration for the volume.

### How long does a peptide last after reconstitution?

That depends on the compound and its supplier’s stability data, so no single figure applies. Check the product’s documentation.

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