The Pool Surface Area Calculator calculates the water surface area of a swimming pool and the interior area of its floor and walls.
Pool Surface Area Calculator
Water surface area and interior (floor + walls) area of rectangular, round, oval and kidney-shaped swimming pools.
Water surface area is the shape’s top area (length × width for a rectangle, πd² ÷ 4 for a round pool). Interior area adds the walls, which equal the pool perimeter times the average depth. Choose a rectangular, round, oval or kidney-shaped pool and enter its size in feet or meters.
Formula
| Pool shape | Water surface area | Interior area (floor + walls) |
|---|---|---|
| Rectangular | A = L × W | A = LW + 2D(L + W) |
| Round | A = πd² ÷ 4 | A = πd² ÷ 4 + πdD |
| Oval | A = π × L × W ÷ 4 | A = πLW ÷ 4 + perimeter × D |
| Kidney | A ≈ 0.45 × (A + B) × L | — |
Where:
- L = length; W = width; d = diameter
- D = average depth = (shallow end + deep end) ÷ 2
- A, B (kidney) = widths at the wide and narrow ends
The oval wall length uses Ramanujan’s approximation for the perimeter of an ellipse.
How the Calculation Works
Step 1: Calculate the area of the pool’s outline at the waterline. This is the water surface area.
Step 2: Calculate the perimeter and multiply it by the average depth. This is the wall area.
Step 3: Add the floor (the same as the water surface area for a flat-sided pool) and the walls to get the interior area.
Variables Explained
| Variable | Meaning | Unit |
|---|---|---|
| L, W | Pool length and width | ft, m |
| d | Diameter of a round pool | ft, m |
| D | Average depth | ft, m |
| A | Area | ft², m², yd² |
Example Calculation
Rectangular pool
Given: 32 ft × 16 ft, average depth 5 ft
Water surface: 32 × 16 = 512 ft²
Walls: 2 × 5 × (32 + 16) = 480 ft²
Result: interior area = 512 + 480 = 992 ft²
Round above-ground pool
Given: diameter 24 ft, depth 4 ft
Water surface: 3.14159 × 24² ÷ 4 ≈ 452.39 ft²
Walls: 3.14159 × 24 × 4 ≈ 301.59 ft²
Result: interior area ≈ 753.98 ft²
Common Area Conversion Table
| Unit | Equivalent |
|---|---|
| 1 m² | 10.7639 ft² |
| 1 yd² | 9 ft² |
| 100 ft² | 9.29 m² |
Material Estimation Notes
Which area to use
- Water surface area: pool covers, solar covers, heater sizing and evaporation estimates.
- Interior area: pool paint, plaster, resurfacing, tile or liner quantities.
Paint or coating quantity depends on the product’s coverage rate, the surface condition and the number of coats — check the manufacturer’s data sheet and divide the interior area by its stated coverage.
Steps, benches and sloped floors
The formulas treat the floor as flat and the walls as vertical. Steps, benches and a sloping floor add some extra surface, so allow extra material for them.
Dimensions Explained
Average depth
For a pool with a shallow and deep end, add the two depths and divide by 2. A pool 3 ft deep at one end and 8 ft at the other has an average depth of 5.5 ft.
Kidney pools
Kidney-shaped pools vary, so the result uses a commonly used approximation. For an exact figure, measure the outline as coordinates and use the Irregular Shape Area Calculator.
Frequently Asked Questions
How do you calculate the surface area of a pool?
For the water surface, use the shape’s area: length × width for rectangles, π × radius² for round pools.
How do I calculate the square footage of a pool for resurfacing?
Add the floor area and the wall area (perimeter × average depth). The interior area output does this for you.
How do you find the surface area of a round pool?
A = π × (diameter ÷ 2)². A 24 ft round pool has about 452 ft² of water surface.
What size pool cover do I need?
Start from the water surface area and the pool’s outer dimensions; cover makers usually specify how much overlap to add.
How do you find the surface area of a kidney-shaped pool?
A widely used approximation is 0.45 × (wide-end width + narrow-end width) × length.