How the pool surface area calculator works
Water surface is the flat top of the pool. Interior surface adds the floor and the four walls, which is what a painter or plaster crew charges against.
Solar heating panels are sized as a share of water surface, usually 50 to 100 percent, so this number decides how many panels go on the roof.
The formula, step by step
Interior Area = Surface Area + (Perimeter x Average Depth)
- Find the water surface area from the pool shape.
- Find the perimeter of the pool.
- Multiply perimeter by average depth to get wall area.
- Add wall area to surface area for the total interior finish area.
Worked example
A 16 by 32 foot rectangle with an average depth of 5 feet.
Water surface = 512 square feet. Perimeter = 96 feet.
Wall area = 96 x 5 = 480 square feet. Interior total = 512 + 480 = 992 square feet of finish.
Watch it done
This short video walks through the same job in real life, so you can match what you see on screen to what you do at the pool.
Tips before you start
Covers are cut to the water surface plus an overlap. Add 2 feet to each side for an above ground cover and check the manufacturer chart before ordering.
One gallon of pool paint covers roughly 200 to 250 square feet in a single coat. Two coats on a 992 square foot interior means about 8 to 10 gallons.
Pool Surface Area Calculator FAQs
How do I calculate the surface area of a pool?
Multiply length by width for a rectangle. For a round pool, use 3.14 times the radius squared. The result is in square feet.
Is surface area the same as square footage?
Yes. Pool square footage almost always means the water surface, unless a paint or plaster quote says interior surface.
What size solar cover do I need?
Buy a cover that matches the water surface and trim it to fit. A cover slightly larger than the pool works better than one that comes up short.
Why does surface area affect heating?
Almost all heat loss happens at the water surface through evaporation. Double the surface and you roughly double the heat you have to replace.