How the bleach water purification calculator works
The US Environmental Protection Agency's emergency guidance gives a set number of drops per gallon depending on the bleach's strength. Cloudy, colored or very cold water gets a double dose.
8.25% bleach: 6 drops per gallon (12 if cloudy)
Drops = drops per gallon × gallons · 1 tsp ≈ 96 drops
Let cloudy water settle and filter it through a clean cloth or coffee filter first. Stir after adding bleach and let it stand for at least 30 minutes. Use regular unscented bleach that lists sodium hypochlorite as the active ingredient; scented, color-safe and splash-less products are not suitable. Bleach does not remove chemical contamination and is less effective against some parasites such as Cryptosporidium, which is why boiling for one minute (three minutes above 6,500 ft) remains the preferred method.
Worked example
To treat a 5-gallon container of clear water with 8.25% bleach, add 6 × 5 = 30 drops, about a third of a teaspoon. Stir, wait 30 minutes and check for a faint chlorine smell. If the water were cloudy, you would use 60 drops.
Frequently asked questions
How much bleach do I add to a gallon of water?
8 drops of 6% bleach or 6 drops of 8.25% bleach for clear water, double for cloudy water, per EPA guidance.
How long should treated water sit?
At least 30 minutes before drinking.
Can I use scented bleach?
No. Use only plain, unscented bleach with sodium hypochlorite.
Is boiling better than bleach?
Boiling for one minute is the most reliable way to kill pathogens; bleach is a backup when boiling is not possible.
Updated October 2026. Results are estimates for education, not financial or medical advice. All math runs in your browser; nothing you type is sent anywhere.