Bleach dilution calculator explained
Household bleach needs to be diluted to reach the chlorine strength recommended for labs, food facilities, or healthcare spaces. This calculator uses the relationship and a 1.05 g/mL density for typical 5-6% sodium hypochlorite to tell you how much concentrate to add for any target ppm and final volume.
Use it when writing SOPs, mixing mop buckets, or preparing daily spray bottles so every batch lands in the safe but effective range outlined by public health agencies.
How the conversion works
Bleach dilutions follow mass balance:
where is the stock bleach strength (w/w % NaOCl), is the volume of concentrated bleach to add, is the desired free chlorine concentration (often in mg/L or ppm), and is the final solution volume. The calculator converts to mg/mL using the 1.05 g/mL density so all terms share the same basis before solving for .
Units and conversions
| Quantity | Units | Notes |
|---|---|---|
| Stock bleach strength | % NaOCl | Most household bleach is 5.25-6.15%; check the label. |
| Target concentration | mg/L (ppm) | 1000 ppm = 0.1% available chlorine. |
| Final volume | L or mL | Enter the total amount you plan to mix. |
| Stock volume | mL | Calculator reports how much bleach to measure. |
Convert gallons to liters by multiplying by 3.785 and ounces to milliliters by multiplying by 29.57 if needed.
Worked examples
- 1000 ppm disinfectant for benches
Stock bleach: 6.0% NaOCl. Need at .
Measure 70 mL of bleach, add water until total volume reaches 4 L, and mix gently.
- Sanitizing 250 gallon storage tank
Target in using 5.25% bleach.
Split the 9.0 L concentrate into several additions around the tank for even mixing.
Tips and pitfalls
- Always add bleach to water, not the other way around, to limit splashes.
- Mix fresh solutions daily; hypochlorite decomposes in light and heat.
- Wear gloves and eye protection when handling concentrated bleach, even for small batches.
- Verify the bleach label concentration annually because formulations drift with supply changes.