# Bleach Dilution Calculator URL: https://speedycalculator.com/calculators/chemistry/bleach-dilution/ Last updated: 2026-10-30 > The bleach dilution calculator tells you how much household bleach to add to water to reach a target chlorine level in ppm – for disinfecting surfaces, sanitising dishes or treating water – and gives the dilution ratio and the amount of water to add. ## Inputs - Bleach strength on the label (sodium hypochlorite) (%) - How to read the percentage - Bleach density (g/mL, g/cm³, kg/m³, kg/L, lb/ft³) — About 1.07–1.12 g/mL for household bleach; check the safety data sheet. - Target is expressed as - Target concentration (ppm (mg/L), % (g/100 mL), g/L) - Amount of diluted solution to make (L, mL, US gal, qt (US), cup (US), fl oz (US), tbsp (US), tsp (US), UK gal, m³) ## Results - Hypochlorite needed - Bleach to add - Water to add - Dilution ratio (parts water per 1 part bleach) - Final strength as available chlorine - Use ## Formula ``` Mass of NaOCl needed (mg) = target (mg/L) × final volume (L) · Bleach volume = mass ÷ (bleach % ÷ 100 × density × 1,000 mg/g) · Ratio = 1 : (V_final ÷ V_bleach − 1) ``` ## Explanation Household chlorine bleach is a water solution of sodium hypochlorite (NaOCl), usually 5–8.25% on the label in North America and 3–5% in many other countries. Used straight it is far stronger than needed and damages surfaces and skin, so it is always diluted to a target concentration expressed in parts per million (ppm, equal to mg per litre). Typical targets are about 50–200 ppm for sanitising food-contact surfaces and dishes, around 1,000 ppm for general disinfection, and around 5,000 ppm for heavy contamination. The arithmetic is a dilution: the mass of hypochlorite in the bleach you measure out must equal the mass in the finished solution. Because the label percentage is by mass, a precise answer uses the bleach density (about 1.07–1.12 g/mL); many guidelines simply treat the percentage as grams per 100 mL, which is within about 10%. You can also express the target as "available chlorine" (the Cl₂ equivalent used by some standards), which is 0.952 times the NaOCl figure. Always add bleach to cold water, never mix bleach with ammonia, vinegar or other cleaners, and make a fresh solution daily because hypochlorite slowly decomposes. ### How to use the Bleach Dilution Calculator - **Bleach strength on the label (sodium hypochlorite)** - **How to read the percentage** - **Bleach density** — About 1.07–1.12 g/mL for household bleach; check the safety data sheet. - **Target is expressed as** - **Target concentration** - **Amount of diluted solution to make** Results update as you type, every field has its own unit menu, and everything is calculated in your browser. ### How it works The calculator multiplies the target concentration by the final volume to get the milligrams of hypochlorite needed, divides by the hypochlorite content of the bleach (percent × density) to get the bleach volume, and subtracts that from the final volume to give the water to add and the dilution ratio. ### Worked example Make 1 US gallon (3.785 L) of 1,000 ppm disinfecting solution from 6% bleach (simple reading). Hypochlorite needed = 1,000 mg/L × 3.785 L = 3,785 mg. The bleach holds 6 g per 100 mL = 60,000 mg/L, so the bleach volume = 3,785 / 60,000 = 0.0631 L = 63.1 mL, about 4¼ tablespoons. Add it to 3.72 L of water; the ratio is about 1 : 59. With the exact reading (density 1.08 g/mL) the bleach holds 64,800 mg/L and you need 58.4 mL instead. ### Strength of common household recipes (6% bleach, simple reading) RecipeApproximate strength1/8 tsp per US gallon≈ 10 ppm (emergency drinking water)1 tbsp per US gallon≈ 233 ppm (sanitising)1/3 cup per US gallon≈ 1,220 ppm (disinfecting)4 tsp per US quart≈ 1,220 ppm (disinfecting)1 part bleach + 9 parts water (1:9)6,000 ppm (heavy contamination) ### Tips - Use the final volume of the solution, not the volume of solvent added, for molarity. - For dilutions, C₁V₁ = C₂V₂ only holds when both concentrations use the same unit. - Add acid to water, never water to acid. - Everything is calculated in your browser. ### Common mistakes to avoid - Mixing w/w, w/v and v/v percentages. - Forgetting that pH is logarithmic – one unit is a tenfold change in [H⁺]. - Using pKa where Ka is asked for (or the other way round). ### Inputs explained FieldWhat to enterBleach strength on the label (sodium hypochlorite)In %How to read the percentageChoose one: Simple: % = grams per 100 mL (common guidance), Exact: % by mass, use the bleach densityBleach densityUnits: g/mL, g/cm³, kg/m³, kg/L, lb/ft³. About 1.07–1.12 g/mL for household bleach; check the safety data sheet.Target is expressed asChoose one: ppm of sodium hypochlorite, ppm of available chlorine (Cl₂)Target concentrationUnits: ppm (mg/L), % (g/100 mL), g/LAmount of diluted solution to makeUnits: L, mL, US gal, qt (US), cup (US), fl oz (US) … ### What each result means - **Bleach to add** = [Hypochlorite needed]÷[Hypochlorite in the bleach] - **Water to add** = [Amount of diluted solution to make] - [Bleach to add] - **Dilution ratio (parts water per 1 part bleach)** = [Amount of diluted solution to make]÷[Bleach to add] - 1 - **Final strength as available chlorine** = [Hypochlorite needed]÷[Amount of diluted solution to make]×70.906÷74.442 ## Worked example Inputs — Bleach strength on the label (sodium hypochlorite): 6 %; How to read the percentage: Simple: % = grams per 100 mL (common guidance); Target is expressed as: ppm of sodium hypochlorite; Target concentration: 1,000 ppm (mg/L); Amount of diluted solution to make: 1 L. Results — Hypochlorite needed = 1,000 mg NaOCl; **Bleach to add = 16.6667 mL**; Water to add = 0.9833 L; Dilution ratio (parts water per 1 part bleach) = 59; Final strength as available chlorine = 952 ppm; Use = Disinfecting strength (hard surfaces, bathrooms). ## Key terms - **Sodium hypochlorite**: NaOCl, the active ingredient of chlorine bleach. - **ppm**: Parts per million; for water solutions 1 ppm ≈ 1 mg/L. - **Available chlorine**: Hypochlorite content expressed as an equivalent mass of chlorine gas, Cl₂. - **Dilution ratio**: Parts of water added per part of bleach, written 1 : x. ## FAQ **How much bleach per gallon of water for disinfecting?** Common guidance for 5.25–8.25% bleach is 5 tablespoons (1/3 cup) per gallon, or 4 teaspoons per quart. With 6% bleach that gives roughly 1,200 ppm sodium hypochlorite. **What does ppm mean for bleach?** Parts per million by mass, which for water solutions is the same as milligrams per litre. 1,000 ppm = 0.1% = 1 g per litre. **How much bleach to sanitise dishes?** About 1 tablespoon of 6% bleach per gallon of water gives roughly 230 ppm; many food-safety codes ask for 50–200 ppm with a contact time of at least one minute. **How do I disinfect drinking water with bleach in an emergency?** US EPA guidance for 6% unscented bleach is about 1/8 teaspoon (8 drops) per gallon of clear water, about 10 ppm, then wait 30 minutes. Use double for cloudy water. **Why does my bleach strength matter?** Concentrated (8.25%) bleach needs about 27% less product than 6% bleach for the same ppm; older bleach loses strength, so use a fresh bottle. **What is available chlorine?** The oxidising power expressed as the mass of Cl₂ it is equivalent to. One mole of NaOCl (74.44 g) equals one mole of Cl₂ (70.91 g), so available chlorine = 0.952 × NaOCl. **How long does diluted bleach last?** Diluted solutions lose strength within a day, faster in sunlight and warmth – mix a fresh batch each day. ## Sources - [US EPA – Emergency disinfection of drinking water](https://www.epa.gov/ground-water-and-drinking-water/emergency-disinfection-drinking-water) - [PubChem – National Library of Medicine](https://pubchem.ncbi.nlm.nih.gov/) - [OpenStax – Chemistry 2e](https://openstax.org/details/books/chemistry-2e)