Pool Volume & Chemical Calculator
Enter your pool's shape and depths and get the volume in gallons, liters, and cubic feet — then the doses that follow from it: cal-hypo or trichlor to hit your free-chlorine target, soda ash or muriatic acid for pH, and baking soda for alkalinity. Works in feet or meters, with a to-scale plan and side view.
Private by design. Your pool dimensions, test readings, and every dose calculation stay in your browser — nothing is uploaded to a server.
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Standard pool dosing chart (per 10,000 gallons)
Every dose below comes from one identity: 1 ppm means 1 pound of active ingredient per 1,000,000 pounds of water, and a US gallon of water weighs about 8.345 lb. Divide by the product's strength and you have the pounds of product. These are the constants the calculator scales to your volume.
| Chemical | What it changes | Dose per 10,000 gallons | Watch out for |
|---|---|---|---|
| Cal-hypo, 65% | Free chlorine +1 ppm | 2 oz (0.13 lb) | Adds calcium hardness; pre-dissolve in a bucket to avoid bleaching a vinyl liner |
| Trichlor, 90% | Free chlorine +1 ppm | 1.5 oz (0.09 lb) | Adds cyanuric acid and is acidic — CYA creeps up over a season |
| Soda ash (sodium carbonate) | pH +0.2 | 6 oz | Can cloud the water briefly; also nudges alkalinity up |
| Muriatic acid, 31.45% | pH −0.4 | 1 qt (32 fl oz) | Pour slowly into deep water with the pump running; never mix with chlorine |
| Baking soda (sodium bicarbonate) | Total alkalinity +10 ppm | 1.5 lb | Raises pH a little as well — retest both before dosing again |
- Target ranges for a residential pool: free chlorine 1–3 ppm, pH 7.4–7.6, total alkalinity 80–120 ppm, and cyanuric acid 30–50 ppm in an outdoor pool. Fix alkalinity before chasing pH — alkalinity is what makes pH stay put.
- pH doses assume alkalinity near 100 ppm. A pool at 200 ppm alkalinity resists pH changes and needs noticeably more acid; a pool at 40 ppm swings on almost nothing, which is the real problem to fix.
How to calculate pool volume in gallons
- Pick the shape. Rectangle, round, oval, or kidney/freeform. Round pools ask for a diameter; the others ask for length and width at the widest points.
- Measure both depths. Enter the water depth at the shallow end and at the deep end. For a flat-bottom above-ground pool, leave the deep end blank — the calculator treats it as flat.
- Read the volume. You get US gallons, liters, cubic feet or cubic meters, water surface area, average depth, and the pump flow needed for an eight-hour turnover.
- Dose the water. Enter your test-kit readings for free chlorine, pH, and total alkalinity next to your targets. The tool converts your volume into pounds, ounces, and fluid ounces of each chemical.
Frequently Asked Questions
- How do you calculate pool volume in gallons?
- Surface area × average depth gives cubic feet; one cubic foot holds 7.48 US gallons. A 32 × 16 ft rectangle averaging 5.5 ft deep is 2,816 ft³, or about 21,000 gallons. Average depth is simply (shallow + deep) ÷ 2 for a constant-slope floor.
- How accurate is the kidney/freeform estimate?
- It multiplies the length × width bounding box by 0.75, the rule of thumb pool techs use for freeform shapes. Expect ±10% — fine for chemical dosing, but measure carefully if you are buying a liner or a heater.
- How much cal-hypo raises chlorine by 1 ppm?
- About 2 oz of 65% cal-hypo per 10,000 gallons. That comes straight from the definition of ppm: 1 ppm × 10,000 gal × 8.345 lb/gal ÷ 1,000,000 = 0.128 lb of pure chlorine, divided by 0.65 available chlorine.
- Should I use cal-hypo or trichlor?
- Cal-hypo is unstabilized and raises calcium hardness; trichlor is stabilized, acidic, and adds cyanuric acid with every dose. Trichlor is convenient in a floater or feeder, but if your CYA is already above 50 ppm, switch to cal-hypo or liquid chlorine so the chlorine stays effective.
- Why does the tool tell me to add half the dose first?
- pH and alkalinity responses depend on your current alkalinity, temperature, and fill water, so any chart is a starting point. Add roughly half, run the pump for a full turnover, then retest — overshooting pH downward is much harder to undo than sneaking up on it.
- Is anything uploaded?
- No. Every calculation and both diagrams render entirely in your browser — your pool dimensions and test readings never leave the page.
Use Cases
- Size a chlorine or shock dose from your actual pool volume
- Work out how much baking soda a low-alkalinity pool needs
- Estimate gallons for a new above-ground or freeform pool
- Check whether your pump moves enough GPM for an eight-hour turnover
- Convert a metric pool plan into US gallons for chemical labels