Knowing how many gallons your pool holds is the first step to getting chemistry right, sizing a pump or heater, and estimating the cost of a refill. Enter the shape and a few measurements and the calculator works out surface area, average depth, gallons, liters, and the weight of the water, updating as you type. Switch between feet and meters at any time and your numbers are converted in place.
Keeping fish instead of swimmers? The aquarium volume calculator handles tank shapes with glass and substrate deductions. For backyard projects, the pond liner calculator sizes a liner, and the unit converter covers any other gallon, liter, or cubic-foot conversion. For the water sitting in the plumbing, the pipe volume calculator works out volume and weight by pipe diameter and length.
Frequently asked questions
How do I calculate how many gallons are in my pool?
Multiply the surface area by the average depth to get cubic feet, then multiply by 7.48 — the number of US gallons in one cubic foot. For a rectangle that is length × width × average depth × 7.48; for a round pool it is 3.14 × radius² × depth × 7.48. A 32 × 16 ft pool that goes from 3.5 ft to 8 ft deep averages 5.75 ft, which is 2,944 cubic feet or about 22,000 gallons. In meters, cubic meters × 1,000 gives liters directly.
How do I get the average depth of a pool with a deep end?
Add the shallow-end depth and the deep-end depth and divide by two. That assumes the floor slopes evenly, which is close enough for most plaster and vinyl pools. If your pool has a long flat shallow section and a short hopper-shaped deep end, the true average is a little lower — split it into two sections, or measure depth every few feet along the length and average those readings. Measure to the actual water line rather than the top of the coping, which is usually 4–6 inches higher.
What formula is used for kidney-shaped and freeform pools?
Kidney pools use the pool-industry rule of thumb: 0.45 × length × (A + B) × average depth, where A and B are the widths of the two rounded ends measured at their widest. That 0.45 factor comes from pool-supply and chemical-dosing guides and gets most kidney shapes within about 5–10 %. For truly freeform pools, break the outline into rectangles and circles, work out each area, and add them — or use the L-shape option for pools that are two rectangles joined together.
Is an oval above-ground pool an ellipse?
Usually not. Most above-ground 'oval' pools are really a rectangle with a half-circle on each end, which holds more water than a true ellipse of the same length and width. Choose 'Oval, straight sides' for those. Pick 'Oval (ellipse)' only for in-ground pools with a genuinely egg-shaped outline. For a 15 × 30 ft pool at 4 ft, the straight-sided version holds about 12,000 gallons versus about 10,600 for a true ellipse — a big difference when you are dosing chemicals.
Why does the pool volume matter for chemicals and pumps?
Every chemical dose on a label is written per 10,000 gallons, so a 20 % error in volume means a 20 % error in chlorine, pH, or salt. Volume also sizes the pump: to turn the water over in 8 hours, divide the gallons by 480 to get the gallons per minute the pump must actually deliver. The dosing helper here does the straight ppm math, but chlorine demand, sunlight, and stabilizer all change the real result, so follow the product label and retest after adding anything.