# Antibiotic Working Concentration (C₁V₁ = C₂V₂)

Compute the antibiotic stock volume for a target working concentration with C₁V₁ = C₂V₂, supporting mg/mL, µg/mL, g/L, ng/mL and × fold notation.

> Canonical page: https://elysiatools.com/en/tools/antibiotic-concentration

- **Category:** Health

- **Keywords:** antibiotic working concentration, c1v1 c2v2, dilution calculator, antibiotic stock, mg/ml to ug/ml, ampicillin, kanamycin, media supplement, working solution, lab calculator, microbiology, sterile dilution

## Overview

Calculate the antibiotic stock volume needed to reach a target working concentration with the C₁V₁ = C₂V₂ formula. Enter stock and working concentrations in mg/mL, µg/mL, g/L, ng/mL or × fold units plus the final medium volume to receive the stock volume in mL and µL, the remaining medium volume, and the dilution factor.

## Inputs

- **Stock concentration** (number): Concentration of the stock solution (e.g. ampicillin 100 mg/mL).
- **Stock concentration unit** (select)
- **Working concentration** (number): Desired final concentration in the medium (e.g. 50 µg/mL).
- **Working concentration unit** (select)
- **Final (working) solution volume** (number): Total volume of medium + stock to prepare.
- **Final volume unit** (select)
- **Decimal places** (number)

## When to use

- When adding ampicillin, kanamycin or another antibiotic stock to LB or similar culture medium.
- When converting a concentrated stock (mg/mL or 1000×) into a µg/mL or 1× working solution.
- When you need the exact pipette volume and remaining medium volume for a given final volume.

## How it works

- Enter the stock concentration and choose its unit (mg/mL, µg/mL, g/L, ng/mL or × fold).
- Enter the desired working concentration with its unit and the total final volume in µL, mL or L.
- The tool converts units, applies C₁V₁ = C₂V₂ and returns the stock volume (mL and µL), medium volume to add and dilution factor.

## Use cases

- Prepare 100 mL LB-ampicillin at 50 µg/mL from a 100 mg/mL stock.
- Dilute a 1000× antibiotic stock to 1× in 500 mL of medium.
- Calculate the stock volume needed for kanamycin or chloramphenicol selection plates.

## Frequently asked questions

### What formula does the calculator use?

It uses C₁V₁ = C₂V₂ so that stock volume V₁ equals working concentration times final volume divided by stock concentration.

### Which concentration units are supported?

mg/mL, µg/mL, g/L, ng/mL and × (fold concentration) for both stock and working values.

### Can stock and working concentrations use different units?

Yes. Units are converted automatically, so a 100 mg/mL stock can be paired with a 50 µg/mL working concentration.

### What volume units can I enter?

Final volume accepts µL, mL or L. Results always report stock volume in both mL and µL.

### What typical working concentrations are used?

Common values include ampicillin 50–100 µg/mL and kanamycin 25–50 µg/mL; follow your own protocol.

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