Pool Chlorine Calculator: How Much Chlorine Do You Need to Add?

Need to figure out how much chlorine or bleach to add to your swimming pool to clean it and balance your water chemistry? You can follow the steps below and use my pool chlorine calculator that I built to figure it out in just a minute or two. Below, I go over all the chlorine measurements you need and correct calculations no matter what chlorine type you use. Let’s get started.

Here are the steps you need to take:

Test Your Pool Water

First, you need to test your swimming pool water with a testing kit to figure out your current free chlorine level. Free chlorine is the amount of water in your pool that is available for disinfecting. This is different than the combined chlorine and total chlorine levels. I go over all the differences in my article linked above. If you need help testing your pool water or need a test kit, I linked my research above as well.

For your backyard pool, free chlorine should be around 2-4 ppm (parts per million), ideally nestled around 3 ppm. For commercial pools, 3-5 ppm is fine.

Do you have your reading? If so, let’s move on.

Measure Your Pool Volume

Next, you need to measure how many gallons of water are in your pool. You can use my calculator below to figure that out. And you can check out my dedicated volume calculator page for more information on the math behind it.


Done with that? Let’s move on.

Select Your Type of Chlorine

There are several types of chlorine you can add to your pool as a sanitizer. You can also add bleach. In my calculator below, you’ll select the type of chlorine you have. If you’re adding bleach or cal-hypo, I also included a field for the concentration percentage, which affects how much you should add.

I am working on a big article comparing the different types of chlorine you can use. I’ll link that here once it is complete. I also have several guides on specific chlorine types, which I linked below.

Calculate How Much to Add

Alright, now it’s time to put everything together and calculate how much chlorine or bleach you need. In the calculator below, select your chemical of choice, approximate pool volume, current free chlorine level, and desired free chlorine level. Also, be sure to fill out the concentration percentage field if you’re using bleach or cal-hypo.

If your chlorine level is too low, the final value will be the amount of that chemical you need to add, measured in ounces (oz).

If your chlorine level is too high, the final value will be zero. Your chlorine level should naturally drop over time, so it’s best to do nothing. If it’s dangerously high, though, you should drain some pool water and replace it with fresh water to dilute the chlorine concentration.


You should be all set now. For more of my maintenance research, head to my articles on how to maintain a pool and swimming pool chemicals 101.

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