How to use the pool chemical dose calculator
- Enter the pool volume and choose gallons or liters. If you are unsure of the volume, the pool volume calculator will work it out from the size and depth.
- Choose whether you know the change wanted in ppm, or the current and target readings, and enter the numbers.
- Choose the product type, liquid or dry, and enter the available chlorine percent from the label. The example 12.5% is a label value you should replace with your own.
- Read the amount to add in fluid ounces and milliliters for a liquid, or ounces, grams and pounds for a dry product. The steps show every conversion.
Formula
Active chlorine in grams = liters x ppm change / 1,000
Liquid product in liters = grams / (percent x 10), with percent by volume
Dry product in grams = grams / (percent / 100), with percent by weight
1 ppm is 1 milligram per liter. A liquid labeled 12.5% by volume holds 125 grams of available chlorine in each liter. One US gallon is 3.785411784 liters, one US fluid ounce is 29.5735295625 milliliters and one ounce is 28.349523125 grams.
Raising 10,000 gallons by 1 ppm
10,000 US gallons is 37,854.11784 liters. Raising it by 1 ppm needs 37,854.11784 x 1 / 1,000 = 37.85 grams of available chlorine. A liquid at 12.5% by volume holds 125 grams per liter, so you need 37.85 / 125 = 0.3028 liters, which is 302.8 milliliters or 10.24 US fluid ounces.
With a dry product at 65% available chlorine by weight, the same change needs 37.85 / 0.65 = 58.2 grams, which is 2.05 ounces by weight or 0.128 pounds.
Reading a product label
Chlorine products state the share of available chlorine in different ways. Liquid bleach style products are often given as a trade percent, which this tool treats as grams of available chlorine per 100 milliliters. Some labels give a percent by weight instead. A liquid that is denser than water holds more chlorine in each liter than the same percent by volume, so the dose by volume would be smaller than shown here.
If you are unsure, check the label for grams per liter or the density of the product. Dry products such as calcium hypochlorite or dichlor are given by weight, so the dry setting applies. Stabilized products add other chemicals to the water, which this tool does not track.
Safety and testing
This tool does arithmetic only. It cannot know your water chemistry, your test kit's accuracy or how fast sun and swimmers use chlorine up. Test the water, add less than the full dose if in doubt, wait for the water to circulate, and test again.
Follow the directions and safety warnings printed on your product. Never mix chemicals together, keep them away from children and pets, and add product to water rather than water to product. For other volume and unit work, see the unit converter and the volume calculator.
Assumptions and limits
- One part per million is one milligram per liter. The result is for water only and ignores other chemicals already in the pool.
- Liquid strength is read as percent by volume. Dry strength is read as percent by weight.
- The pool volume you enter is accurate. A wrong volume gives a wrong dose in the same proportion.
- The tool does not account for chlorine loss, stabilizer or any other chemical balance such as pH.
Frequently asked questions
How much liquid chlorine raises a pool by 1 ppm?
In 10,000 US gallons, 1 ppm needs about 10.24 fluid ounces of a 12.5% liquid. The amount scales with pool size and the change you want, and shrinks as the product gets stronger.
Why does a stronger product need less?
Because it holds more available chlorine in each ounce. Doubling the percent halves the amount needed for the same ppm change.
What does ppm mean for a pool?
Parts per million. In water, 1 ppm equals 1 milligram of the substance in each liter, so a pool at 3 ppm free chlorine has 3 milligrams in every liter.
Can I use this for something other than chlorine?
The arithmetic is the same for any product that changes a concentration in ppm, if you enter its percent of active ingredient. The safety notes and label directions for that product still apply.