---
title: "Dilution and concentration calculator — free, runs in your browser"
description: "C₁V₁ = C₂V₂, plus percentage, molarity and ppm conversions. Free, no sign-up, and nothing you enter leaves your browser."
url: https://atoneplace.net/tools/dilution-calculator/
site: "At One Place"
---

# Dilution and concentration calculator

C₁V₁ = C₂V₂, plus percentage, molarity and ppm conversions.

## How it works

Solves the dilution equation for whichever value is missing, and converts between percentage, molarity, ppm and mg/L.

The dilution equation works because the amount of solute does not change — only the volume it is spread through. Concentration times volume is that amount, so the product is the same on both sides.

One safety point that belongs on any page about this: always add acid to water, never water to acid. Dilution releases heat, and adding water to concentrated acid concentrates that heat in a small volume at the surface, which can boil and spatter acid. Adding acid to a larger volume of water spreads the heat through the bulk.

For dilute aqueous solutions, 1% by mass is about 10,000 ppm and 1 mg/L is about 1 ppm, because a litre of water weighs a kilogram. That approximation breaks down for concentrated solutions and for anything not water-based.

> This tool runs entirely in your browser. Nothing you enter is sent to a server, logged or stored, and the page keeps working with the network disconnected.

## Common questions

### What is the dilution formula?

C₁V₁ = C₂V₂. The amount of solute is unchanged, so concentration times volume is equal before and after.

### Do you add acid to water or water to acid?

Acid to water, always. Dilution is exothermic, and adding water to concentrated acid concentrates that heat at the surface where it can boil and spatter.

### How do percent and ppm relate?

For dilute aqueous solutions, 1% is roughly 10,000 ppm, since a litre of water weighs a kilogram. The approximation fails for concentrated or non-aqueous solutions.

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## Sources

- Calculated on this page — At One Place (/about/)