What this calculator does
Household and commercial bleach is sold as a percentage concentration of sodium hypochlorite, but sanitising and disinfecting guidelines are almost always given as a target concentration in parts per million (ppm) of free available chlorine. Converting between the two, and working out how much stock bleach to add to a given volume of water, is the same dilution equation used throughout chemistry: C₁V₁ = C₂V₂.
Bleach concentration varies by product and by country, and even the "same" product is often reformulated over time, so the stock percentage on the label matters more than any rule of thumb. This calculator converts that percentage to ppm (roughly 10,000 ppm per 1% sodium hypochlorite, treating the dilute solution as having a density close to water) and solves directly for the volumes needed.
The formula
Convert the stock bleach percentage to ppm by multiplying by 10,000. Multiply the target concentration by the final volume wanted to get the total "chlorine units" needed, then divide by the stock concentration in ppm to get the volume of bleach required; the rest of the final volume is water.
| Term | Meaning |
|---|---|
| Stock concentration | The percentage of sodium hypochlorite on the bleach bottle label, converted to ppm. |
| Target concentration | The free-chlorine strength wanted in the final solution, in ppm, as specified by a sanitising or disinfecting guideline. |
| Dilution ratio | The volume of bleach needed per unit volume of water, expressed as 1 part bleach to however many parts water. |
The inputs explained
| Field | What to enter |
|---|---|
| Stock bleach concentration (%) | The percentage of sodium hypochlorite shown on the bleach product label; this varies by brand and region, so check the actual bottle rather than assuming a standard figure. |
| Target concentration (ppm) | The target free-chlorine concentration for the intended use, taken from the relevant sanitising or disinfecting guideline. |
| Final solution volume wanted (mL) | The total volume of diluted solution you want to end up with. |
When to use it
Mixing a food-contact sanitising solution
Food safety guidelines commonly specify a target in the low hundreds of ppm for sanitising surfaces that touch food, well below the concentration used for general disinfection.
Mixing a disinfecting solution
Disinfecting against more resistant pathogens typically calls for a higher target concentration, in the low thousands of ppm, than routine sanitising.
Working with different bleach strengths
Bleach sold for laundry, cleaning or commercial/industrial use often has a different stock percentage; recalculating with the actual label strength avoids under- or over-diluting compared with a recipe written for a different product.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How much bleach is needed for different target strengths
A standard 8.25% stock, diluted to a range of target concentrations.
| Target concentration | Bleach needed | Dilution ratio (bleach : water) |
|---|---|---|
| 50 ppm | 0.61 mL | 1 : 1,649.0 |
| 100 ppm | 1.21 mL | 1 : 824.0 |
| 200 ppm | 2.42 mL | 1 : 411.5 |
| 500 ppm | 6.06 mL | 1 : 164.0 |
| 1000 ppm | 12.12 mL | 1 : 81.5 |
| 3000 ppm | 36.36 mL | 1 : 26.5 |
How much bleach is needed at different stock strengths
A fixed 200 ppm target, sourced from a range of stock bleach percentages.
| Stock bleach concentration | Bleach needed | Stock concentration |
|---|---|---|
| 5% | 4.00 mL | 50,000 ppm |
| 6% | 3.33 mL | 60,000 ppm |
| 8.25% | 2.42 mL | 82,500 ppm |
| 10% | 2.00 mL | 100,000 ppm |
| 12.5% | 1.60 mL | 125,000 ppm |
Questions
Why does the calculator convert bleach percentage to ppm using 10,000?
A 1% concentration by weight is, for a dilute aqueous solution with a density close to that of water, approximately 10,000 mg per litre, and ppm for a dilute aqueous solution is essentially mg per litre. This is an approximation that is standard practice for household bleach dilution, not an exact chemical conversion.
What target concentration should I use?
That depends entirely on the guideline governing the specific use, whether food-contact sanitising, general disinfection, or another purpose, and varies by jurisdiction and application. This calculator only performs the dilution arithmetic once a target ppm has been decided.
What if my stock bleach concentration is not on the label?
Check the product's safety data sheet, which lists the sodium hypochlorite percentage, since formulations vary between products and can change over time even for the same brand name.
What happens if the target concentration is higher than the stock?
The calculator flags this, since it is impossible to dilute a solution to a strength higher than its starting concentration; a stronger stock bleach or undiluted product would be needed instead.
For the underlying dilution formula in a general laboratory context, see the solution dilution calculator. For step-wise dilutions instead of a single mixing step, see the serial dilution calculator.