SAFETY NOTICE: High-concentration hydrogen peroxide (35%+) is corrosive and can cause severe burns. Always wear gloves and eye protection. When mixing, add peroxide to water to prevent splashing.
How to Dilute Hydrogen Peroxide
Hydrogen peroxide (H2O2) is a versatile chemical used for everything from gardening and cleaning to industrial whitening. However, it is often sold in concentrated "food grade" forms (usually 35%) which are too strong for direct use. Diluting it correctly is essential for safety and effectiveness.
The Dilution Formula
This calculator uses the standard chemical dilution equation: C1 × V1 = C2 × V2
C1: Concentration of the starting (stock) solution.
V1: Volume of the starting solution needed.
C2: Desired final concentration.
V2: Desired final total volume.
Common Concentration Uses
Concentration
Common Application
0.5% – 1%
Plant foliar spray and root rot prevention.
3%
Standard household disinfectant and first aid.
6% – 12%
Hair bleaching and professional cleaning.
30% – 35%
Industrial use and "Food Grade" concentrate.
Step-by-Step Guide to Mixing
1. Identify your concentrations: Check the label of your bottle. Most food-grade H2O2 is 35%. Most household needs require 3%.
2. Calculate: Use the calculator above to find the exact volume of concentrate and distilled water needed.
3. Water First: To minimize the risk of a concentrated splash, it is best practice to measure out your water first and then slowly add the hydrogen peroxide into the water.
4. Storage: Store your diluted solution in a dark, opaque bottle. Light breaks down H2O2 into water and oxygen, causing it to lose its potency quickly.
Dilution Example
If you have 35% food-grade peroxide and you want to make 1000ml of a 3% solution:
(3% × 1000ml) / 35% = 85.7ml of peroxide.
1000ml – 85.7ml = 914.3ml of distilled water.
Mix the 85.7ml of concentrate into the 914.3ml of water.
function calculateH2O2() {
var c1 = parseFloat(document.getElementById('stockConc').value);
var c2 = parseFloat(document.getElementById('targetConc').value);
var v2 = parseFloat(document.getElementById('targetVol').value);
var unit = document.getElementById('volUnit').value;
var resultDiv = document.getElementById('hpResult');
var resultText = document.getElementById('resultText');
if (isNaN(c1) || isNaN(c2) || isNaN(v2) || c1 <= 0 || c2 <= 0 || v2 = c1) {
alert("Target concentration must be lower than the stock concentration.");
return;
}
// V1 = (C2 * V2) / C1
var v1 = (c2 * v2) / c1;
var waterNeeded = v2 – v1;
var v1Fixed = v1.toFixed(2);
var waterFixed = waterNeeded.toFixed(2);
resultText.innerHTML = "To make " + v2 + " " + unit + " of " + c2 + "% hydrogen peroxide from a " + c1 + "% stock solution, you need:" +
"• " + v1Fixed + " " + unit + " of Concentrated Peroxide" +
"• " + waterFixed + " " + unit + " of Distilled Water";
resultDiv.style.display = 'block';
}