What this calculator does
The Pool Chlorine Dosage Calculator tells you how much chlorine product to add to your swimming pool to raise the free chlorine concentration from its current level to your target level. It works for any liquid or granular chlorine product as long as you know its available (active) chlorine percentage.
How to use it
Enter your pool's volume in gallons, the current free chlorine reading (from a test kit, in ppm), your desired target ppm (typically 1–3 ppm for residential pools), and the available chlorine percentage printed on your product label. The calculator returns the dose in fluid ounces, with cups and quarts shown for convenience.
The formula explained
The constant 0.0000834 converts a one-ppm change across one gallon into ounces of pure (100% available) chlorine. Multiplying by gallons and by the ppm increase gives the pure-chlorine demand; dividing by the product's available fraction scales that up to the actual amount of your specific product. In short: $$\text{oz} = \dfrac{(\text{target}_{ppm} - \text{current}_{ppm}) \times \text{gallons} \times 0.0000834}{\%_{available}/100}$$.
Worked example
For a 15,000-gallon pool currently at 1 ppm, raising to 3 ppm using 10% liquid chlorine: \(\Delta\text{PPM} = 2\), so $$\text{oz} = \frac{(2 \times 15{,}000 \times 0.0000834)}{0.10} = \frac{2.502}{0.10} = 25.02 \text{ fluid ounces}$$ — about 3.1 cups.
FAQ
What target ppm should I use? Most pools are kept between 1 and 3 ppm of free chlorine. Raise it higher only for shock treatment.
My product is granular — does this still work? Yes, but the result is a volume estimate (fluid ounces). For granular products, weigh by label dose for best accuracy; the ounce figure here is a useful approximation.
Why did it return zero? If your target is at or below the current level, no chlorine is needed, so the calculator returns 0.
