How this chlorination calculator works
This calculator estimates how much chlorine product you need to raise free chlorine from your current level to your target level. It works for both liquid chlorine (bleach/sodium hypochlorite) and granular products (such as calcium hypochlorite), based on the product strength you enter.
The math behind it is straightforward: 1 ppm is 1 mg/L. Once we know your water volume in liters and your desired ppm increase, we compute the amount of available chlorine needed, then convert that into product quantity using the concentration (%).
Step-by-step usage
1) Enter pool or tank volume
Type your water volume and choose gallons or liters. If you only have rough dimensions, estimate volume first (length × width × average depth × conversion factor).
2) Add current and target free chlorine
Use a recent water test reading for current free chlorine (FC). Then enter your desired FC level. If target is less than or equal to current, no chlorine addition is needed.
3) Choose product type and strength
- Liquid chlorine: usually 5% to 12.5% sodium hypochlorite
- Granular chlorine: often 65% to 73% available chlorine
Always use the label’s available chlorine percentage when possible.
4) Review the dosage output
The tool returns practical dosing units:
- Liquid: mL, liters, fluid ounces, cups
- Granular: grams, ounces, pounds
Example calculation
Suppose you have a 15,000 gallon pool at 1.0 ppm FC, and you want to reach 3.0 ppm using 10% liquid chlorine.
- Required increase: 2.0 ppm
- Calculated available chlorine mass based on water volume
- Converted to product amount using 10% strength
The calculator gives an estimated liquid dose in multiple units so you can measure quickly.
Best practices for chlorination
- Test water before and after dosing.
- Add chemicals gradually and circulate water thoroughly.
- Never mix chlorine products directly together.
- Store chlorine in a cool, dry, ventilated area away from acids.
- Wear gloves and eye protection when handling concentrated products.
Important notes
This chlorination calculator gives a practical estimate, not a substitute for local regulations, manufacturer instructions, or professional water treatment guidance. Real-world demand can vary due to sunlight, bather load, organics, pH, and stabilizer (CYA).
If your chlorine is dropping unusually fast, test and balance pH, alkalinity, and cyanuric acid before repeatedly adding more sanitizer.