How do you convert bleach percentage to ppm?

Multiply the sodium hypochlorite percentage by 10,000. Household bleach at 5.25%–6.15% contains about 52,500–61,500 ppm available chlorine; a 1:10 dilution gives about 5,250–6,150 ppm, and 1:100 about 525–615 ppm.

What bleach concentration kills C. diff spores?

CDC’s disinfection guideline notes that regular bleach at 5,000 ppm available chlorine can inactivate C. difficile spores in 10 minutes or less. In practice, use an EPA-registered sporicidal product (EPA List K) and follow its label for dilution and contact time.

How long does diluted bleach last?

CDC notes that diluted hypochlorite in tap water, stored at room temperature in closed opaque plastic containers, can lose up to 40%–50% of its available chlorine over a month. Prepare dilutions fresh, or follow your facility’s and the product’s instructions.

Free tool · CIC® exam topic

Bleach dilution calculator

Enter your bleach strength, the target concentration and the volume you need. The calculator gives the amount of bleach and water, and the ratio.

Result

Bleach: 83.3 mL
Water: 916.7 mL
Mixing ratio: 1 part bleach + 11 parts water
Final dilution: 1:12
Stock concentration: 60,000 ppm

How the calculation works

Stock ppm = bleach % × 10,000 (6% bleach ≈ 60,000 ppm available chlorine).
Bleach needed = target ppm × final volume ÷ stock ppm.
Water = final volume − bleach.

Example: 5,000 ppm from 6% bleach, 1,000 mL total: 5,000 × 1,000 ÷ 60,000 = 83.3 mL of bleach plus 916.7mL of water (1 part bleach + 11 parts water).

What CDC’s disinfection guideline says

Household bleach (5.25%–6.15% sodium hypochlorite) contains 52,500–61,500 ppm available chlorine.
Small blood spills: a 1:100 dilution of 5.25%–6.15% bleach (about 525–615 ppm).
Large blood spills: a 1:10 (final concentration) solution of household bleach.
C. difficile: regular bleach at 5,000 ppm available chlorine can inactivate C. difficile spores in 10 minutes or less.

“1:10” means one part bleach in ten parts total (1 part bleach + 9 parts water). Many hospitals now use ready-to-use EPA-registered products instead of mixing bleach; if you do mix it, label the container with the concentration and date.

Test yourself: a CIC-style question

What is the minimum concentration of sodium hypochlorite (bleach) commonly recommended for environmental disinfection during C. difficile outbreaks?

0.05% (500 ppm)
0.1% (1,000 ppm)
0.5% (5,000 ppm)
5.25% (52,500 ppm)

Show answer

C. 0.5% (5,000 ppm)

A 1:10 dilution of household bleach gives roughly 5,000 ppm (0.5%) available chlorine, the concentration shown to inactivate C. difficile spores. Alcohol and quaternary ammonium compounds are not sporicidal.

Questions like this come up in the Environment of Care domain of the CIC® exam. The 654 questions in the app each come with a written explanation.

FAQ

How do you convert bleach percentage to ppm?: Multiply the sodium hypochlorite percentage by 10,000. Household bleach at 5.25%–6.15% contains about 52,500–61,500 ppm available chlorine; a 1:10 dilution gives about 5,250–6,150 ppm, and 1:100 about 525–615 ppm.
What bleach concentration kills C. diff spores?: CDC’s disinfection guideline notes that regular bleach at 5,000 ppm available chlorine can inactivate C. difficile spores in 10 minutes or less. In practice, use an EPA-registered sporicidal product (EPA List K) and follow its label for dilution and contact time.
How long does diluted bleach last?: CDC notes that diluted hypochlorite in tap water, stored at room temperature in closed opaque plastic containers, can lose up to 40%–50% of its available chlorine over a month. Prepare dilutions fresh, or follow your facility’s and the product’s instructions.

Sources

Checked against CDC on October 21, 2026. For education only. Always follow the EPA-registered product label (dilution, contact time, safety) and your facility’s policy. Never mix bleach with ammonia or acids.