Bleach Dilution Calculator — C₁V₁ = C₂V₂
Enter your stock bleach concentration, the target working concentration and the total volume you need to prepare — get the exact millilitres of bleach and water to measure out.
%
%
L
Measure this volume of stock bleach; fill to total volume with water
- 1
Apply C₁V₁ = C₂V₂ → V₁ = C₂ × V₂ / C₁
0.5% × 1 L ÷ 5% = 0.1 LThe amount of active ingredient is conserved during dilution. - 2
Convert litres to millilitres
0.1 × 1 000 = 100
How does this calculator work?
Use V_bleach = (C_target × V_total) / C_stock to calculate how much stock bleach to add. Example: 5% household bleach diluted to 0.5% in 1 L = 100 mL bleach + 900 mL water. Always add bleach to water; never mix with ammonia or acidic cleaners; discard the prepared solution after 24 hours.
Formula
How this is calculated
The dilution equation C₁V₁ = C₂V₂ states that the amount of active ingredient is conserved during dilution. Multiplying stock concentration C₁ (%) by the volume of stock added V₁ equals the target concentration C₂ times the final volume V₂. Rearranging gives V₁ = C₂ × V₂ / C₁. The water to add is simply V₂ − V₁. For dilute solutions (< 10%) the density is close to water, so volume-percent approximations introduce negligible error.
Household bleach is sold at roughly 3–6% sodium hypochlorite (NaOCl); industrial or pool bleach runs 10–15%. Common target concentrations by use-case: 0.5% (5 000 ppm) for general surface disinfection per WHO guidance; 0.1% (1 000 ppm) for routine hard surfaces; 1% (10 000 ppm) for blood spills or heavily contaminated areas; 0.01–0.05% (100–500 ppm) for food-contact surfaces. All these are mass-percent values — multiply by 10 000 to convert to ppm.
Always add bleach to water (not water to bleach) to minimise splashing, and use cold or room-temperature water — hot water accelerates NaOCl decomposition. Freshly prepared solutions are most effective; discard and prepare new solution after 24 hours. Never mix bleach with ammonia or acidic cleaners.
Frequently asked questions
1% = 10 000 ppm (parts per million) for dilute aqueous solutions near water density. So 0.5% NaOCl = 5 000 ppm, the WHO recommendation for surface disinfection. Divide ppm by 10 000 to get percent; multiply percent by 10 000 to get ppm.
Yes — NaOCl degrades at roughly 0.5–1% of its concentration per day at room temperature, faster in heat or sunlight. A bottle stored for six months may have lost 20–50% of its original strength. For critical applications, test stored bleach with a pool test strip and adjust the calculation accordingly.
No — never mix bleach with ammonia (forms toxic chloramine gas), with acidic cleaners such as vinegar or toilet-bowl cleaners (releases chlorine gas), or with other disinfectants. Always dilute bleach with plain cold water only, and use in a well-ventilated area.
Also known as
TG we-Calculate Editorial Team. (2026). Bleach Dilution Calculator — C₁V₁ = C₂V₂ [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/bleach-dilution-calculator
TG we-Calculate Editorial Team. "Bleach Dilution Calculator — C₁V₁ = C₂V₂." TG we-Calculate. 2026. https://we-calculate.com/calculator/bleach-dilution-calculator.
TG we-Calculate Editorial Team, "Bleach Dilution Calculator — C₁V₁ = C₂V₂," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/bleach-dilution-calculator
@misc{wecalculate_bleach_dilution_calculator, title = {Bleach Dilution Calculator — C₁V₁ = C₂V₂}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/bleach-dilution-calculator}}, year = {2026}, note = {TG we-Calculate} }
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