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Bleach Disinfectant Dilution Calculator

How much bleach and water to mix for cleaning in an outbreak: 1,000 ppm for surfaces, toilets and the sick room, and 10,000 ppm for blood spills, the two strengths NHS infection-control guidance uses.

From the guide Pandemic & Outbreak Survival: cleaning & disinfection →

What are you mixing?

Use
On the label as sodium hypochlorite or available chlorine. UK bleach is usually about 3–5%.
A spray bottle is usually 500 ml; a bucket 5–10 L.
Mix –

Bleach (yellow) in water

Leave it wet for

Spoons

⚠️ Safety

  • Never mix bleach with other cleaners, especially acids (toilet cleaners, limescale removers, vinegar) or ammonia: it releases toxic chlorine gas. Don't pour it straight onto urine.
  • Use cold water, add the bleach to the water, wear rubber or nitrile gloves, and open a window.
  • Clean first with detergent and water: bleach doesn't work well on dirty surfaces.
  • Make a fresh mix every day in a labelled container, out of reach of children. Diluted bleach loses strength within a day.
  • Plain (thin) bleach mixes more evenly than thick bleach. Rinse food surfaces with clean water afterwards. Bleach corrodes metal and fades fabric.

Which strength for what

JobStrengthHow
Door handles, light switches, taps, phones, worktops in an outbreak1,000 ppmAfter cleaning; leave wet at least 5 minutes, then rinse food surfaces
Toilets and the sick room's bathroom1,000 ppmClean, then disinfect at least daily
Vomit or diarrhoea, once cleaned up1,000 ppmSoak it up with paper towels or cat litter first, then clean, then disinfect
Blood spills10,000 ppmCover with paper towels soaked in the solution; leave at least 3 minutes
Laundry with vomit or faeces–Wash separately at 60 °C

Strengths from the NHS England National Infection Prevention and Control Manual. There is no official UK household dilution; these mixes are calculated from those strengths (bleach % × 10,000 = ppm). Hospitals use chlorine tablets or granules, which are more reliable if you can get them. Alcohol hand gel doesn't kill norovirus: wash hands with soap and water.

Water treatment calculatorBleach drops to make drinking water safe. Room ventilation calculatorAir changes for the sick room. Setting up a sick roomFrom the Pandemic guide.