Enter your water volume and bleach concentration — get the exact dose in ml and fluid ounces for safe drinking water treatment, tank disinfection, or surface sanitation.
Select use type, enter volume and bleach strength to get exact dosage
Safety first: Never mix bleach with ammonia, vinegar, or other cleaners. Use only unscented household bleach (sodium hypochlorite) for drinking water treatment. Always ventilate the area.
What are you treating?
Enter your measurements
Water Volume
Bleach Strength
Common bleach concentrations
⚠ Please enter a valid water volume (greater than zero) and bleach concentration (0.1%–20%).
WaterTankCalculator.com — Bleach Dosage Results
Your Results
Bleach to Add
—
millilitres (ml)
Fluid Ounces
— fl oz
Drops (20 drops/ml)
— drops
Teaspoons
— tsp
Chlorine Dose
— mg/L
Water Volume
— L
Use Type
—
Bleach Dose Visualisation
📖 How To Use
How to Use This Calculator
Getting the correct bleach dose takes under a minute:
Select your use type
Choose "Drinking Water" for potable water treatment, "Tank Disinfection" for cleaning storage tanks, or "Surface Sanitation" for disinfecting food-contact surfaces. Each use case requires a different chlorine concentration.
Enter your water volume
Enter the total volume of water you need to treat. Use litres, US gallons, UK gallons, millilitres, or cubic metres — select the unit that matches your container or tank label.
Enter your bleach concentration
Check the label on your bleach bottle. Most US household bleach today is 6% or 8.25% sodium hypochlorite; older or budget bottles may be 5.25%. Use the quick-set buttons for common strengths.
Read your result
The calculator shows the exact bleach volume to add in ml, fluid ounces, drops, and teaspoons. For small volumes, use drops for precision; for large tanks, use ml.
Mix and wait
Add the measured bleach to the water and stir. For drinking water, wait at least 30 minutes. The water should have a slight chlorine smell; if it doesn't, EPA advises repeating the dose and waiting another 15 minutes.
Important: If water is cloudy, let it settle and filter it through a clean cloth or coffee filter first, then tick "cloudy" in the calculator to double the dose. Always verify with a chlorine test strip if treating water for vulnerable people.
📐 The Formula
Bleach to Water Ratio Formula
The dosage is calculated from the required chlorine concentration and your bleach's sodium hypochlorite content:
For drinking water, the calculator uses 6.5 mg/L, which matches the US EPA emergency table: 8 drops of 6% bleach or 6 drops of 8.25% bleach per gallon. It then works out the bleach volume from your bottle's strength.
Target Chlorine Doses by Use
Use Type
Target Free Chlorine
Source
Contact Time
Drinking Water (clear)
6.5 mg/L (ppm)
US EPA emergency guidance
30 min
Drinking Water (cloudy or cold)
13 mg/L (ppm)
US EPA emergency guidance (double dose)
30 min
Tank Disinfection
50 mg/L (ppm)
Common tank shock practice — drain before use
12–24 hr
Surface Sanitation
200 mg/L (ppm)
Food-contact sanitizing level
Per product label
Common Bleach Quick Reference
Use / Volume
5.25% Bleach
6% Bleach
8.25% Bleach
Drinking: 1 L
0.12 ml
0.11 ml
0.08 ml
Drinking: 1 US gal
0.47 ml
0.41 ml
0.30 ml
Drinking: 20 L
2.5 ml
2.2 ml
1.6 ml
Drinking: 100 L
12.4 ml
10.8 ml
7.9 ml
Tank: 1,000 L
952 ml
833 ml
606 ml
Tank: 5,000 L
4,762 ml
4,167 ml
3,030 ml
💡 Use Cases
When to Disinfect Water with Bleach
🚨
Emergency / Disaster
Floods, pipe failures, and boil-water advisories can contaminate tap water. Chlorination is the fastest reliable method when clean water access is interrupted.
🛢️
New or Cleaned Tanks
Before first use and after any repair or cleaning, storage tanks must be disinfected. Biofilm and bacteria establish within 24 hours in untreated water.
🏕️
Off-Grid & Camping
River, rainwater, and borehole water may carry pathogens. Bleach treatment is lightweight, cheap, and effective against bacteria and most viruses.
🌿
Agricultural Irrigation
Livestock water troughs and irrigation systems require periodic disinfection to prevent bacterial contamination that can affect animal health and crop safety.
What Bleach Does (and Doesn't) Kill
Sodium hypochlorite at the recommended doses is effective against bacteria (E. coli, Salmonella, Vibrio cholerae), most viruses (including hepatitis A, norovirus), and many protozoan cysts. It is not effective against Cryptosporidium without extended contact times at very high doses — for water suspected of Cryptosporidium contamination, use a 1-micron filter or boiling instead.
❓ FAQ
Frequently Asked Questions
What is the bleach to water ratio for drinking water?
For clear water, the US EPA recommends 8 drops of 6% bleach or 6 drops of 8.25% bleach per US gallon, which is about 2 drops per litre. Double it for cloudy, coloured or very cold water. Stir, wait 30 minutes, and check for a slight chlorine smell before drinking.
Can I use any bleach for water treatment?
Only use unscented sodium hypochlorite bleach with no added thickeners or surfactants. Scented bleach, gel bleach, or bleach marketed for laundry with added fragrances should never be used for drinking water. Always check the label — it must list sodium hypochlorite as the only active ingredient.
How much bleach do I need to disinfect a 1,000 litre water tank?
For tank disinfection (50 mg/L target), using 5.25% bleach: approximately 952 ml (just under 1 litre) of bleach per 1,000 litres of water. Fill the tank, add the bleach, circulate if possible, and leave for 12–24 hours. Then drain, rinse, and refill with fresh water.
How do I know if I've added too much bleach?
Over-chlorinated water has a strong, sharp chlorine smell and may cause throat irritation. The treated water is still safe — just aerate it by pouring between containers repeatedly or letting it stand uncovered for several hours. The excess chlorine will dissipate. Use a chlorine test strip to confirm the level has dropped to under 4 mg/L before drinking.
Does bleach expire? Does old bleach still work?
Yes. Sodium hypochlorite degrades over time — and can lose a noticeable share of its strength within a year, faster in heat. Bleach more than a year old should not be used for water treatment unless the concentration can be verified. Store bleach in a cool, dark place and replace annually for emergency preparedness kits.
How long does chlorinated water stay safe?
Properly chlorinated water stored in a sealed, clean container in a cool location remains safe for up to 6 months. If stored in a container that has been opened or exposed to sunlight, residual chlorine dissipates faster — retest or re-treat every 3 months. Use our Safe Water Storage Duration Calculator for precise estimates.
What is the difference between chlorine dosage for drinking water vs. tank disinfection?
Emergency drinking water treatment uses about 6.5 mg/L (the EPA drop table), low enough to drink after 30 minutes. Tank disinfection uses 50 mg/L — about 8 times higher — to kill bacteria embedded in biofilm on tank walls. This is a shock treatment: the water must be drained after disinfection and is not drinkable at tank disinfection concentrations.
Is there a calculator for chlorine dosage specifically?
Yes — our dedicated Chlorine Dosage Calculator allows custom mg/L target inputs for precise water treatment applications, including pool treatment and industrial water systems. The bleach-to-water calculator you're using now is designed for household and emergency use with preset doses based on EPA guidance.
✅ Sources & Review
Sources and review
The doses and steps on this page come from these references:
Reviewed by John Mac, PE, Water Systems Specialist
Texas-licensed Professional Engineer with 13+ years in residential water storage and 180+ tank projects. John writes and reviews every calculator on this site.
