Bleach Dilution Calculator
Bleach only works well when it is diluted correctly. Too weak and it may not kill germs. Too strong and it wastes bleach, harms surfaces and gives off more fumes without doing a better job. Choose the job, enter how much water you are using, and the calculator gives the amount of regular household bleach to add. It uses the ratios published by the CDC and the USDA.
Never mix bleach with ammonia, vinegar, rubbing alcohol or any other cleaner. Mixing can release gases that are dangerous to breathe. Dilute it with plain water only.
Bleach-to-water ratios
| Job | Bleach per gallon of water | Per quart (32 fl oz) | Contact time |
|---|---|---|---|
| Disinfecting household surfaces (CDC) | 1/3 cup (about 5 tbsp) | 4 tsp | Keep visibly wet for at least 1 minute |
| Sanitizing cutting boards and food-contact surfaces (USDA) | 1 tbsp | 3/4 tsp | Let stand several minutes, rinse, air-dry |
| Norovirus cleanup: vomit, diarrhea (CDC) | 5 to 25 tbsp (1/3 cup to about 1 1/2 cups) | 1 1/4 to 6 1/4 tbsp | At least 5 minutes |
| Mouse or rat droppings and urine (CDC) | 1 1/2 cups (1 part bleach to 9 parts water) | 6 tbsp | Soak 5 minutes; don’t sweep or vacuum |
These ratios are for regular, unscented household bleach that contains 5% to 9% sodium hypochlorite. The percentage is printed on the label. The CDC advises not to use a product if the percentage is outside that range or not listed. If your bottle gives its own dilution directions, follow the label. Scented, gel and “splash-less” bleaches are usually not meant for disinfecting or for surfaces that touch food, so check before you use them.
How to disinfect with bleach, step by step
- Clean first. Wash off dirt, grease and food with soap or detergent and water. Bleach works poorly on dirty surfaces.
- Mix in a ventilated room. Add the bleach to room-temperature water, not hot water. Wear gloves, and consider eye protection if you are mixing a large batch.
- Apply and wait. Wipe or spray the solution on and leave the surface wet for the contact time in the table. Don’t wipe it off right away.
- Rinse food-contact surfaces with clean water, then let them air-dry or pat them dry with clean paper towels.
- Make a fresh batch every day. Diluted bleach loses strength, and the CDC says it is no longer effective after about 24 hours.
- Label spray bottles and store them away from children and pets.
For rodent droppings, the CDC’s advice is to air out the space first, wear gloves and spray rather than sweep or vacuum, which can put virus particles into the air. Our guide to getting rid of mice covers the full cleanup.
Bleach can discolor fabrics and damage natural stone such as marble, some metals and many finishes. For cutting boards specifically, see how to clean a cutting board.
Common questions
How much bleach per gallon of water to disinfect?
The CDC says 1/3 cup (5 tablespoons) of regular household bleach per gallon of room-temperature water, or 4 teaspoons per quart.
How much bleach goes in a spray bottle?
For disinfecting: 4 teaspoons in a 32-ounce bottle, 3 teaspoons in a 24-ounce bottle and 2 teaspoons in a 16-ounce bottle, topped up with water. Label the bottle and mix a fresh one each day.
Is a stronger mix better?
Not for everyday disinfecting. At the right contact time, the CDC ratio is enough. Extra bleach mainly adds fumes and wear on surfaces. The stronger end of the range is meant for norovirus cleanup.
Should I use bleach on mold?
The EPA does not recommend chlorine bleach as a routine way to clean up mold. Detergent and water plus fixing the moisture problem matter more. Use our mold cleanup calculator to check whether a patch is small enough to handle yourself.