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 does “1:10” mean for a bleach dilution?

One part bleach in ten parts total: 1 part bleach plus 9 parts water. With 5.25%–6.15% household bleach that gives roughly 5,250–6,150 ppm available chlorine, the concentration CDC cites for large blood spills.

Is the CRCST exam going to ask me to calculate dilutions?

HSPA’s content outline includes chemical preparation following the manufacturer’s instructions for use, including dilution. Expect questions on reading the IFU, using the correct dilution and contact time, and why too much or too little chemical causes problems.

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 · CRCST 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.

“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.

Dilutions on the CRCST exam

HSPA’s CRCST content outline lists chemical preparation that follows the manufacturer’s instructions for use (IFU): the dilution, the right equipment, the expiration date and the correct cleaning agent. The same rule applies to detergents, enzymatic cleaners and disinfectants: measure, don’t guess, and respect the contact time. Try the Spaulding classification tool for which level of disinfection an item needs.

Test yourself: a CRCST-style question

A technician mixes a disinfectant at twice the dilution the manufacturer’s IFU specifies, “to be safe.” What is the most likely result?

Faster disinfection with no drawbacks
Chemical residue and possible damage to devices and surfaces
The contact time can be cut in half
The solution never needs to be changed

Show answer

B. Chemical residue and possible damage to devices and surfaces

Stronger is not better. Using more chemical than the IFU specifies can leave residue, damage instruments and surfaces, and expose staff to more fumes. Too little chemical, or too short a contact time, risks inadequate disinfection. Follow the IFU for dilution and contact time.

Questions like this come up in the Cleaning, Decontamination and Disinfection section of the CRCST exam. The 901 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 does “1:10” mean for a bleach dilution?: One part bleach in ten parts total: 1 part bleach plus 9 parts water. With 5.25%–6.15% household bleach that gives roughly 5,250–6,150 ppm available chlorine, the concentration CDC cites for large blood spills.
Is the CRCST exam going to ask me to calculate dilutions?: HSPA’s content outline includes chemical preparation following the manufacturer’s instructions for use, including dilution. Expect questions on reading the IFU, using the correct dilution and contact time, and why too much or too little chemical causes problems.
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 November 13, 2026. For education only. Always follow the product’s instructions for use and EPA label (dilution, contact time, safety), your facility’s policy and the SDS. Never mix bleach with ammonia or acids.