Pool chlorine calculator
Enter your pool size and your free chlorine now. The calculator suggests a target from your CYA (the part most chlorine calculators skip) and tells you exactly how much to pour.
- Raise free chlorine 10 ppm
- ~107 fl oz liquid (12.5%) (3.3 qt; 3.2 L), ~19 oz cal-hypo (70%) (539 g), or ~22 oz dichlor (62%) (624 g)
- Raise alkalinity (TA) 10 ppm
- ~1.5 lb baking soda (680 g)
- Raise calcium (CH) 10 ppm
- ~1.2 lb calcium chloride (77% flake) (544 g)
- Raise stabilizer (CYA) 10 ppm
- ~13 oz cyanuric acid (369 g)
- Lower pH 8.0 → 7.6 (at TA 100)
- ~10 fl oz muriatic acid (1.3 cups; 296 mL), or ~0.9 lb dry acid (408 g)
Ballpark for a 10,000-gallon pool. Enter your size and levels below for your exact dose.
Example numbers are filled in so you can see an answer. Type your own over them.
Don't know your gallons? Work it out here →
Exact geometry at 7.48 gal/ft³. Kidney shapes, diving hoppers and salt/turnover figures live in the full Pool Volume Calculator.
How much chlorine raises 1 ppm
Multiply by the ppm you need. These come from the same functions the calculator uses.
| Product | 10,000 gal (37,854 L) | 15,000 gal (56,781 L) | 20,000 gal (75,708 L) | 25,000 gal (94,635 L) | 30,000 gal (113,562 L) |
|---|---|---|---|---|---|
| 12.5% liquid chlorine | 10.7 fl oz (1.3 cups; 316 mL) | 16.0 fl oz (2 cups; 473 mL) | 21.3 fl oz (2.7 cups; 630 mL) | 26.7 fl oz (3.3 cups; 790 mL) | 32.0 fl oz (1 qt; 946 mL) |
| 10% liquid chlorine | 13.3 fl oz (1.7 cups; 393 mL) | 20.0 fl oz (2.5 cups; 591 mL) | 26.7 fl oz (3.3 cups; 790 mL) | 33.3 fl oz (1 qt; 985 mL) | 40.0 fl oz (1.3 qt; 1.2 L) |
| 6% household bleach | 22.2 fl oz (2.8 cups; 657 mL) | 33.3 fl oz (1 qt; 985 mL) | 44.4 fl oz (1.4 qt; 1.3 L) | 55.5 fl oz (1.7 qt; 1.6 L) | 66.7 fl oz (2.1 qt; 2.0 L) |
| 70% cal-hypo | 1.9 oz (54 g) | 2.9 oz (82 g) | 3.8 oz (108 g) | 4.8 oz (136 g) | 5.7 oz (162 g) |
| 62% dichlor (anhydrous) | 2.2 oz (62 g) | 3.2 oz (91 g) | 4.3 oz (122 g) | 5.4 oz (153 g) | 6.5 oz (184 g) |
| trichlor tabs (~90%) | 1.5 oz (43 g) | 2.2 oz (62 g) | 3.0 oz (85 g) | 3.7 oz (105 g) | 4.5 oz (128 g) |
Your target depends on your CYA
CYA (stabilizer) protects chlorine from sunlight, and it also holds most of it in reserve. The more CYA you run, the more free chlorine it takes to do the same job. That is why this calculator asks for CYA and a fixed "3 ppm" answer is wrong for most outdoor pools.
| CYA | Minimum FC | Target FC | Shock (SLAM) |
|---|---|---|---|
| 30 | 2 | 4–6 | 12 |
| 40 | 3 | 5–7 | 16 |
| 50 | 4 | 6–8 | 20 |
| 60 | 5 | 7–9 | 24 |
| 70 | 5 | 8–10 | 28 |
| 80 | 6 | 9–11 | 31 |
| 90 | 7 | 10–12 | 35 |
| 100 | 8 | 11–13 | 39 |
More on why: how chlorine and CYA work together.
What each chlorine adds besides chlorine
- Liquid chlorine and bleach: about 1.7 ppm of salt per 1 ppm of chlorine, and nothing else that builds up.
- Cal-hypo: about 0.8 ppm of calcium hardness per 1 ppm. Fine now and then; a problem as a habit on plaster or a salt cell.
- Dichlor: about 0.9 ppm of CYA per 1 ppm. Useful to build CYA in a new pool, a trap once CYA is where you want it.
- Trichlor tablets: about 0.6 ppm of CYA per 1 ppm, and they lower pH. Convenient, and the usual reason CYA creeps up all summer.
The full comparison, with cost: which chlorine to use.
How to add it
- Pour liquid chlorine slowly in front of a return jet with the pump running.
- Never mix chlorine with acid or with another chlorine product. Add one at a time.
- Retest after the water has circulated for about 30 minutes.
- Add chlorine in the evening if you can: the sun burns off unstabilized chlorine fast.
Doses are dimensional (label strength and gallons), with liquid chlorine at Trouble Free Pool's 12 ppm per gallon of 12.5% per 10,000 gallons. Targets are Trouble Free Pool's FC/CYA chart. Estimates; confirm with your test kit.
FAQ
How much chlorine do I add to my pool?
It depends on three numbers: your pool's gallons, how far you need to raise free chlorine, and the strength of what you pour. In 10,000 gallons, 10.7 fl oz (1.3 cups; 316 mL) of 12.5% liquid chlorine raises free chlorine about 1 ppm. The calculator above does the arithmetic for your pool and your product.
What should my free chlorine be?
There is no single right number: it depends on your CYA (stabilizer). At CYA 30 the target is 4–6 ppm; at CYA 50 it is 6–8; at CYA 80 it is 9–11. Enter your CYA and the calculator suggests a target from the same chart. A flat "3 ppm" is too low for most outdoor pools.
Is liquid chlorine the same as bleach?
Chemically, yes: both are sodium hypochlorite. Pool liquid chlorine is usually 10% or 12.5%, household bleach 6% or 8.25%. Use plain, unscented bleach only. Pick your strength in the calculator, or type the percentage on your jug.
Which chlorine is best for a pool?
Liquid chlorine adds nothing but chlorine and a little salt. Cal-hypo adds about 0.8 ppm of calcium for every 1 ppm of chlorine, dichlor about 0.9 ppm of CYA, and trichlor tablets about 0.6 ppm of CYA. Calcium and CYA only leave by draining, so the "cheap" granular options can cost you a partial drain later.
How many chlorine tablets do I need?
Choose "Trichlor tabs" in the calculator and it converts the dose into 3-inch (8 oz) and 1-inch tablets. Tablets dissolve over days in a feeder or floater, so that is the chlorine they deliver in total, not an instant rise, and every tablet also adds CYA.
When should I shock instead?
When you have algae, cloudy water, or combined chlorine above 0.5 ppm. That calls for the shock (SLAM) level for your CYA, which is several times the normal target. Use the shock calculator for that.