Bleach Dilution Calculator
Work out how to dilute bleach to a target strength for safe cleaning and disinfection. Enter the starting bleach concentration, the volume of bleach you plan to use, and the total final volume, and this calculator gives the final concentration, the water to add, and the dilution ratio.
Formula
C1V1 = C2V2, where C1 = initial concentration, V1 = initial volume, C2 = final concentration, V2 = final volume
- The dilution rule C1V1 = C2V2 says the amount of active chlorine stays the same; only the total volume (and so the concentration) changes.
- Final concentration C2 = (C1 × V1) ÷ V2 — the starting strength times the bleach volume, divided by the total volume.
- Water to add is simply the final volume minus the bleach volume you started with.
- Household bleach is usually about 5.25% sodium hypochlorite; check your label, as concentrations vary.
- For safety, always add bleach to water, never water to bleach, and never mix bleach with ammonia or acids.
100 mL of 5.25% bleach into 1 L
Inputs
- Initial bleach concentration (%): 5.25 %
- Bleach volume to use: 100 mL
- Total final volume: 1000 mL
Diluting 100 mL of 5.25% bleach up to 1000 mL gives (5.25 × 100) ÷ 1000 = 0.525% — a roughly 1:10 solution suitable for disinfecting surfaces. Add 900 mL of water.
Frequently asked questions
How do I dilute bleach correctly?
Use C1V1 = C2V2: multiply the starting concentration by the bleach volume, then divide by the total final volume to find the diluted strength. The water to add is the final volume minus the bleach volume.
What is a 1:10 bleach solution?
It is one part bleach to nine parts water (10 parts total), commonly used for disinfecting after spills of blood or bodily fluids.
What concentration is household bleach?
Most household bleach is around 5.25% sodium hypochlorite, though concentrated versions can be 6–8.25%. Always check the label.
Why add bleach to water and not the reverse?
Adding bleach to water reduces splashing and the concentration of fumes, which is safer for your skin, eyes, and lungs.
How long does diluted bleach stay effective?
Diluted bleach loses potency quickly — prepare it fresh, ideally within 24 hours of use, and store it away from light and heat.