Bleach Dilution Calculator

What this does

So you want to make a chlorine solution from ordinary bleach, for disinfecting, and you do not want to guess the amount. This works it out. You tell it how strong your bleach is, how strong you want the finished solution to be, and how much of it you want to make. It tells you how many millilitres of bleach to add to the water.

How to use it

1. Enter the strength of your bleach as a percentage of sodium hypochlorite. This is on the product label, often around 5 to 6 percent for household bleach.
2. Enter the chlorine concentration you want, in ppm, which is the same as milligrams per litre.
3. Enter the total volume you want to make, and choose litres, US gallons, or Imperial gallons. Then press Calculate.

The result tells you how much bleach to add to that volume of water, for example, "Add 20 millilitres of bleach product to 1 litre of water."

How it works

Bleach is concentrated sodium hypochlorite, and disinfecting solutions are much weaker, so the job is to add a small, measured amount of bleach to a larger amount of water. The calculator takes your three numbers, the strength of the bleach, the strength you are aiming for, and the volume, and works out the millilitres of bleach that will bring the finished solution to roughly your target. It runs entirely in your browser.

One honest point. The maths assumes your bleach is exactly as strong as the label says. In real life bleach gets weaker as it sits on a shelf, and products are labelled differently, so treat the result as a solid starting point rather than a guaranteed exact figure. For anything that really matters, see the safety section below.

Common chlorine strengths

To give you a sense of the targets people aim for, the CDC notes that diluted household bleach of at least 1000 ppm sodium hypochlorite can be used to disinfect surfaces, with the surface kept wet for a contact time of at least one minute and with good ventilation. Stronger solutions, around 5000 ppm, which is roughly a one part bleach to ten parts water dilution of ordinary 5 percent bleach, are used for heavier duty disinfection such as spills. For general surface disinfection, official guidance often gives target concentrations such as 1000 ppm, but the right strength depends on the job, the product, and the setting. Follow your product label and trusted health guidance for the specific use.

These are reference points, not instructions for your particular job. Always follow the directions on your product and any official guidance for what you are actually disinfecting.

Safety, please read this

The most important rule first. Never mix bleach with ammonia, with acids, or with other cleaning products, including many toilet and glass cleaners and vinegar. Doing so releases toxic chlorine and chloramine gas, which can be dangerous. Mix bleach with plain water only. If you ever smell a strong, sharp odour after mixing something, leave the area, get fresh air, and if you feel unwell contact your local poison control or emergency services.

Work somewhere well ventilated, and wear gloves and eye protection. Bleach is corrosive and can irritate or burn skin, eyes, and airways, and it can damage metals and some surfaces. Use cool water, since hot water breaks the chlorine down. Mix your solution fresh and use it within about a day, because it loses strength quickly, and remember that an old bottle of bleach is already weaker than its label. For anything critical, such as food preparation surfaces, healthcare settings, or anything to do with drinking water, do not rely on a calculator, confirm the actual strength with chlorine test strips and follow the official guidance from a health authority. Keep bleach and any solution well away from children and pets, label your containers clearly, and never drink it or use it on or in the body.

This tool is a calculation aid to help with the maths. It is not professional, medical, or safety advice. The responsibility for mixing and using bleach safely is yours, so follow your product's instructions and trusted official guidance.

Questions people ask

References

1. Centers for Disease Control and Prevention. Chemical Disinfectants, Guideline for Disinfection and Sterilization. https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/chemical-disinfectants.html
2. Stanford Environmental Health and Safety. Bleach Solutions (Sodium Hypochlorite). https://ehs.stanford.edu/manual/biosafety-manual/bleach-solutions-sodium-hypochlorite