How to calculate the square footage of a pool
Pool square footage is the surface area of the water seen from directly above, and the formula depends entirely on the pool's shape. A rectangular pool is the easiest: measure the length and width in feet at the waterline and multiply them. A 32 ft by 16 ft pool works out to 512 square feet. Always measure the actual water edge rather than the coping or the deck, because those add area that a cover or liner should not include.
Round pools use the area of a circle: π times the radius squared. The radius is half the diameter, so a 24 ft round pool has a 12 ft radius, and 3.1416 × 12 × 12 gives about 452 square feet. Because the radius is squared, the surface area climbs quickly as the pool gets wider — a 27 ft round pool jumps to roughly 573 square feet. The calculator above handles both the rectangle and circle math, so you only enter dimensions.
Measuring oval, kidney, and irregular pools
Freeform pools rarely fit one clean formula, so the reliable approach is to break them into simple pieces. An oval pool is a center rectangle with a semicircle on each end; measure the straight middle section as a rectangle, then treat the two rounded ends together as one full circle whose diameter is the pool's width. Add those areas for a close estimate. A kidney pool can be approximated as two overlapping circles or as a rectangle with curved ends measured the same way.
For any irregular shape, sketch the pool from above and divide it into rectangles and half-circles you can measure individually. Because these are approximations, round up rather than down when the result feeds a cover or liner order. If you are also finishing the area around the water, measure the concrete deck as its own surface so the two figures stay separate.
Surface area versus the deck and patio
The pool's square footage is only the water surface. The deck, coping, and patio that surround it are separate areas, and mixing them together will oversize a cover or inflate a resurfacing quote. Measure the surrounding hardscape on its own, then combine the numbers only when you genuinely need the total footprint of the pool area.
Once you know the surface area, turning it into a budget is straightforward: multiply the square footage by the price per square foot for your liner, plaster, or cover. The cost calculator does that step for you, so you can compare quotes from resurfacing and liner installers with confidence.