Free Pool Calculators
Chemical dosing, volume, shock and water balance, with the same math Skimmer runs for you.
Quick pool check
Enter today's test. Don't know your gallons? Use the pool volume calculator.
- 1. Add 0.30000000000000004 gal of 12.5% liquid chlorineFree chlorine 1 is below the 2.3 ppm minimum for 30 ppm stabilizer. This brings it to 3.5.
- 2. Add 50 fl oz of muriatic acid (31.45%)pH 7.8 is high. This brings it to about 7.5.
Which pool calculator do I need?
Answer one or two questions, or pick by what the water looks like. 11 calculators, all free.
We'll fill it in on the calculator you pick. Don't know it? Choose the first option.
What are you trying to do?
| Goal | Calculator | You need | Typical chemical |
|---|---|---|---|
| Find my pool's gallons | Pool Volume Calculator | Shape, dimensions, depth | None |
| Dose every reading at once | Pool Chemical Calculator | Gallons and a full test | All of them, in order |
| Is my pool healthy? | Pool Health Check | Test results, equipment answers | Fix plan with doses |
| Raise chlorine or shock | Pool Chlorine Calculator | Gallons, FC, CYA | Liquid chlorine, cal-hypo, dichlor |
| Fix pH | Pool pH Calculator | Gallons, pH, alkalinity | Muriatic acid, soda ash |
| Fix alkalinity | Pool Alkalinity Calculator | Gallons, TA | Baking soda, muriatic acid |
| Fix calcium | Calcium Hardness Calculator | Gallons, CH, surface | Calcium chloride |
| Fix stabilizer | Cyanuric Acid Calculator | Gallons, CYA | Stabilizer |
| Fix salt | Pool Salt Calculator | Gallons, salt reading | Pool salt |
| Check water balance | Pool LSI Calculator | pH, temp, CH, TA, CYA | Whichever lever you pick |
| Budget for a pool | Pool Cost of Ownership Calculator | Yearly costs | None |
New to this? Read what pool chemicals do I actually need.
Balance your water
pH, alkalinity, calcium and stabilizer, one at a time or all at once.
Enter your volume and readings once, get every chemical dose in one in-order plan.
Muriatic acid, dry acid, soda ash or borax, adjusted for your alkalinity.
Baking soda or soda ash to raise TA, muriatic or dry acid to lower it.
Calcium chloride to raise CH, an honest drain-and-refill calculation to lower it.
How much stabilizer to add, the chlorine your CYA needs, or how much to drain.
Langelier Saturation Index corrected for CYA and salt, with doses to get balanced.
Sanitize and shock
Chlorine to hit your target, SLAM levels for a green pool, and salt for a chlorinator.
Size, fill and cost
Every dose starts with your gallons. Then see what the pool really costs.
Diagnose
Not sure what is wrong? Score the pool first, then fix in order.
Ideal pool chemistry ranges
The targets every calculator here doses toward. Full detail per reading in the pool chemistry guide and the printable cheat sheets.
| Reading | Target | Notes |
|---|---|---|
| Free chlorine (FC) | 1 to 3 ppm, or 7.5% of CYA minimum | See the FC by CYA chart below |
| Combined chlorine (CC) | 0 ppm (under 0.5) | Above 0.5, shock |
| pH | 7.4 to 7.6 | 7.2 to 7.8 acceptable |
| Total alkalinity (TA) | 80 to 120 ppm | 60 to 80 for salt pools |
| Calcium hardness (CH) | 200 to 400 ppm plaster | 150 to 250 vinyl and fiberglass |
| Cyanuric acid (CYA) | 30 to 50 ppm | 60 to 80 for salt pools |
| Salt | 2,700 to 3,400 ppm | Check your cell's label |
| LSI | -0.3 to +0.3 | Below -0.3 etches plaster, above +0.3 scales |
Free chlorine by CYA chart
Stabilizer sets how much chlorine you need. Hold FC at or above the minimum, aim for the target, and raise it to the SLAM level to clear algae with the chlorine and shock calculator.
| CYA (ppm) | Minimum FC | Target FC | SLAM / shock FC |
|---|---|---|---|
| 0 | 1 | 2 | 10 |
| 20 | 1.5 | 2.3 | 10 |
| 30 | 2.3 | 3.5 | 12 |
| 40 | 3 | 4.6 | 16 |
| 50 | 3.8 | 5.8 | 20 |
| 60 | 4.5 | 6.9 | 24 |
| 70 | 5.3 | 8.1 | 28 |
| 80 | 6 | 9.2 | 32 |
| 90 | 6.8 | 10.4 | 36 |
| 100 | 7.5 | 11.5 | 40 |
How these calculators work
Each calculator runs the same dosing formulas the Skimmer app uses, in your browser, with nothing sent to a server. Doses assume common retail products unless you pick another strength: 12.5% liquid chlorine, 31.45% muriatic acid, pure baking soda, soda ash and calcium chloride, and 99% stabilizer. pH doses scale with your alkalinity, and chlorine targets follow your stabilizer level. Real water varies, so add about three quarters of a big dose, circulate, retest and finish. The formulas, rounding and sources are written up on our methodology page, and the terms are defined in the pool glossary.
Pool calculator FAQ
Are these pool calculators free?
Yes. Every calculator is free, runs in your browser, and needs no sign-up or email.
Which pool calculator should I use first?
Start with the pool volume calculator if you don't know your gallons, since every dose depends on it. Then use the pool chemical calculator to get every dose from one test, or the picker above to go straight to one reading.
Do the calculators work in liters?
Yes. The volume, chemical, pH and alkalinity calculators switch between US units (gallons, pounds, ounces) and metric (liters, kilograms, grams), and remember your choice.
Why does stabilizer (CYA) change my chlorine target?
Cyanuric acid binds part of your free chlorine, so the more CYA in the water, the more chlorine you need to sanitize. A good rule is a minimum FC of 7.5% of CYA, a target near 11.5%, and 40% to SLAM a green pool.
How accurate are the drain-and-refill numbers?
They assume your fill water has none of the chemical you are lowering and that the drained water is fully replaced. Test your tap water and enter it where the calculator asks, and expect real results to land within a few ppm.
Can I save my pool and readings?
This page remembers your gallons in this browser. To keep every test, dose and reminder in one log, add your pool to the Skimmer app on iPhone.