Bleach Dilution Calculator
Calculate the exact amount of bleach needed for any desired chlorine concentration.
Supports 6 concentration units, 21 volume units, and full bidirectional solving.
Updated September 1, 2026
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What is bleach dilution?
Household bleach is a concentrated sodium hypochlorite solution — typically 5–8.25% available chlorine by weight. Pouring it straight from the bottle is almost never the right move. Whether you are sanitizing food-contact surfaces, disinfecting flood-damaged areas, or maintaining a swimming pool, the chlorine concentration must fall within a specific range to work effectively without causing damage or safety hazards.
This calculator determines the exact volume of bleach you need to mix with water to reach a target chlorine concentration — and it works in both directions. Enter any three known values and the fourth is solved automatically.
The tool supports six concentration units (mg/L, ppm, g/L, and more) and over twenty volume units per field, so you can work in whichever units your recipe, protocol, or local guidelines specify without converting by hand.
How to use this calculator
The calculator connects four quantities. You supply any three and the fourth is derived through the built-in solver.
Enter your bleach concentration
Check the label on your bleach bottle. Typical household bleach is 5.25%–8.25% sodium hypochlorite. Enter this as a percentage — no unit conversion needed.
Set the target chlorine concentration
Enter the desired concentration in the units your guidelines use. For water disinfection, the mg/L (equivalent to ppm) unit is standard. For surface sanitizing, ppm is common.
Enter the desired total volume
How much diluted solution do you need? Enter the volume and pick the matching unit — liters, gallons, cups, or any of the 21 supported volume units.
Read the required bleach volume
The Required bleach volume field shows the answer instantly, with full unit support. The result appears in blue to indicate it was auto-calculated.
Worked example — household disinfection
You have a bottle of 5.25% household bleach and need to prepare 10 L of disinfecting solution at 2 mg/L available chlorine to sanitize a flooded basement.
You need just 0.4 mL of 5.25% bleach mixed into water to reach a total volume of 10 L — a remarkably small amount, which is exactly why accurate calculation matters. Over-dosing bleach wastes product and can leave irritating residues; under-dosing fails to disinfect.
Formula and variables
The calculator uses two linked equations that describe the dilution relationship between bleach concentration, target concentration, solution volume, and required bleach volume.
Combined formula
Variable definitions
What does the 0.105 factor mean?
The constant combines two physical conversions into a single number. It accounts for the density of commercial sodium hypochlorite solution (approximately 1.05 g/mL) and the percentage-to-fraction conversion needed when bleach concentration is expressed as a weight percent. This simplification assumes the bleach product density is close to the typical commercial value; industrial-grade or aged bleach may differ slightly.
Bidirectional solving
The calculator can derive any one unknown from the other three inputs. In practice, the most common direction is solving for , but you can also enter a known bleach volume and the solver will compute the bleach concentration, target concentration, or solution volume that would be required. Fields shown in blue are auto-calculated results.
Common scenarios
Drinking water disinfection
The WHO recommends 0.2–0.5 mg/L free chlorine for household water treatment. For a 20 L storage container using 5.25% bleach:
Swimming pool shock treatment
Pool shock typically requires 10–30 mg/L chlorine depending on the severity. For a 50,000 L pool at 20 mg/L using 8.25% pool-grade bleach:
≈ 12.7 L of 8.25% bleach for the entire pool.
Food-contact surface sanitizing
FDA guidelines recommend 50–200 ppm chlorine for food-contact surfaces. For 1 L of 100 ppm solution using 5.25% bleach:
2 mL of bleach per liter of sanitizing solution.
Tips and best practices
Read the bleach label first
The concentration on bleach bottles is the sodium hypochlorite weight percent — not available chlorine in the chemical sense, though they are numerically identical for standard bleach. Old or improperly stored bleach can lose strength; the label value is the best starting estimate.
mg/L and ppm are equivalent here
For dilute aqueous solutions, 1 mg/L is numerically equal to 1 ppm. The calculator treats them as the same unit internally, so you can switch between them freely.
Bleach degrades over time
Sodium hypochlorite breaks down when exposed to heat, light, and air. Unopened bleach retains most of its strength for about 6–12 months; once opened, use it within 3–6 months for best accuracy. If your bleach is older, the actual concentration may be lower than the label states.
Don't mix bleach with other chemicals
Never mix bleach with ammonia, acids, or other cleaners — this produces toxic gases. Use only clean water for dilution. The calculator assumes water as the sole diluent.
Frequently asked questions
What concentration of bleach should I use?
It depends on the application. For drinking water disinfection, 0.2–0.5 mg/L (ppm) free chlorine is typical. For surface sanitizing, 50–200 ppm is common. Pool shock treatments use 10–30 ppm. Always follow local guidelines or your organization's standard operating procedures.
Can I reverse the calculation — enter the bleach volume and find the concentration?
Yes. The calculator supports bidirectional solving. Enter the bleach volume, target concentration, and desired volume, and it will compute the bleach concentration needed — or enter bleach volume, concentration, and target concentration to solve for the solution volume.
Why does the result change when I switch volume units?
The underlying calculation is always done in consistent base units (mL for bleach volume, L for solution volume). Switching the display unit changes only how the result is shown — the actual amount of bleach required stays the same. For example, 0.4 mL = 0.0004 L — the calculator simply converts between them.
Limitations
•Concentration range. Bleach concentration is limited to 0–30%. Values above this are outside the range of typical commercial products and may not produce reliable results with this formula.
•Density approximation. The factor assumes a bleach solution density of approximately 1.05 g/mL. Industrial, aged, or high-concentration bleach may differ, leading to small errors in the calculated volume.
•Temperature effects not modeled. Chlorine loss and solution density both vary with temperature. The calculator does not apply thermal corrections.
•Not a substitute for testing. For critical disinfection applications (medical, food safety, public water systems), always verify the actual chlorine concentration with a test strip or colorimetric kit after dilution.
Related: Try our Molarity Calculator → for solution concentration problems, or the PPM Calculator → to convert between concentration units.