Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Calculate rectangular or circular pool volume in gallons from your dimensions.
Knowing your pool's true volume in gallons matters for chemical dosing, heater sizing, and fill planning -- this calculator supports both common residential pool shapes (rectangular and circular) and converts cubic feet to gallons using the standard conversion factor.
Choose your pool's shape, then enter its dimensions (length and width for rectangular, or diameter for circular) and its average depth -- pools with a shallow and deep end should use the average of the two, not either extreme.
Rectangular: Volume (cu ft) = Length × Width × Avg Depth
Circular: Volume (cu ft) = π × Radius² × Avg Depth
Gallons = Volume (cu ft) × 7.48
Once you know your gallons, the Pool Water Calculator estimates fill time and water cost, and chemical dosing instructions (chlorine, pH adjusters) are almost always specified per thousand gallons of pool volume.
The calculator is only as good as the three or four numbers you feed it. Measure length and width along the water line rather than the outer edge of the coping or deck, because the coping stones and tile band are not part of the water body. For a circular pool, measure the diameter straight across the center at the water line, not along the curved wall. Depth should be measured from the water surface, not from the top of the pool wall, since most pools are filled to roughly the middle of the skimmer opening, several inches below the rim.
A pool with a flat floor is easy: the average depth is simply the water depth. A pool that slopes evenly from shallow to deep can use the mean of the two end depths. If the bottom has a long flat shallow section and then a steep drop to the deep end, a plain two-number average can be off, and it is better to split the pool into sections and calculate each on its own.
Example with hypothetical numbers: a rectangular pool 32 ft long and 16 ft wide. The first 12 ft is flat at 3.5 ft deep, and the remaining 20 ft slopes from 3.5 ft to 8 ft, which averages 5.75 ft. Section one: 12 x 16 x 3.5 = 672 cu ft. Section two: 20 x 16 x 5.75 = 1,840 cu ft. Total 2,512 cu ft, or about 18,790 gallons. A single average of 5.75 ft over the whole pool would have overstated it at roughly 22,000 gallons.
Treat the gallon figure as an estimate with a margin of error of several percent. That is fine for chemical dosing, where product labels usually give a range, and for sizing a pump or filter by turnover time. If you are ordering a pool cover or liner, rely on the manufacturer's dimensions instead. If you have any doubt, a reliable check is to note the reading on your water meter before and after a fill, which gives a real measured volume.
The calculation assumes vertical walls and a bottom that can be described by a single average depth. Steps, benches, tanning ledges, and rounded corners all shift the true volume slightly, usually making the real figure a little lower than the rectangle formula suggests.
Use the average of the two depths (for example, a pool going from 3ft to 8ft has roughly a 5.5ft average depth) rather than either extreme, since the sloped bottom means the true volume is closer to the average than the maximum.
It's the standard, precise conversion factor between cubic feet and US gallons, used throughout pool, aquarium, and general liquid-volume calculations.
Measure the water body itself at the water line. Coping, tile, and deck edges are outside the water, so including them makes the estimate too high.
Only roughly. The tool models a perfect rectangle or circle. For an irregular shape, split it into simple sections, calculate each, and add them together, or use a meter-based fill measurement.
No. Steps, benches, and ledges displace water, so the true volume can be a little lower than the estimate.
The tool expects feet and returns US gallons. Convert meters to feet first, since one meter is about 3.28 feet.