Square Footage of Pool Calculator
Last updated 15 October 2026
Enter your pool outline and dimensions to get its water-surface area.
Your result will appear here
Enter your measurements, then choose Calculate.
Combine this surface area with water depth to find the volume.
Still unknown or unconfirmed
Formula, sources and blank printable worksheet
AREA-1: rectangle L×W; circle πD²/4; true ellipse πLW/4. Add measured non-overlapping sections.
Calculation version 1.0 uses historical engineering references for arithmetic, not current residential law.
- Sta-Rite Engineering and Design Manual, second edition, 2003, printed pp. 2, 27, 29, 36-40, 44 https://www.pentair.com/content/dam/extranet/nam/pentair-pool/residential/manuals/training/Sta-Rite%20Engineering%20and%20Design%20Manual.pdf
- NIST Handbook 44, Appendix C: US gallon and length units https://www.nist.gov/system/files/documents/2019/11/19/00-20-hb44-final11152019pdf.pdf
| Quantity / unit | Reading | Source and date |
|---|---|---|
| Water outline | ________________ | ________________ |
| Length unit | ________________ | ________________ |
| Waterline length | ________________ | ________________ |
| Waterline width | ________________ | ________________ |
| Waterline diameter | ________________ | ________________ |
| Measured water-surface area | ________________ | ________________ |
| Area unit | ________________ | ________________ |
Mark missing measurements Unknown. Keep exact model, source revision and assumptions with this worksheet. Report a calculation or source correction with reproducible inputs.
This square footage of pool calculator measures the water surface. Use that area for a volume estimate or a stated heat-loss scenario. It does not calculate liner material, tile, walls or the floor's sloped finish area.
A rectangle's water area is length × width. A circle uses π × diameter² ÷ 4. A true ellipse uses π × full length × full width ÷ 4.
Measure at the waterline. Add separate, non-overlapping sections for other outlines. Keep square feet and square metres distinct from gallons: area alone does not tell you the water quantity.
On this page8
Square footage of pool: measure the waterline
Use the inside edge of the water, not the outside of the shell or coping. A tape measurement across the deck may include dry ledges. Record which edge you used so the same measurement can be repeated.
For a circle, measure across the centre. That is the diameter, not the radius. For an ellipse, enter the full long and short dimensions. Its rounded outline must actually match an ellipse. A racetrack outline with straight sides needs sections instead.
Pool calculator area formulas
| Outline | Formula | Artificial example |
|---|---|---|
| Rectangle | Length × width | 32 × 16 = 512 ft² |
| Circle | π × diameter² ÷ 4 | Diameter 20 ft gives about 314.16 ft² |
| True ellipse | π × length × width ÷ 4 | 30 × 15 ft gives about 353.43 ft² |
The equations describe ideal geometry. The displayed decimals reflect arithmetic, not the quality of your tape measurements. Rounding the answer to a useful measurement scale is sensible. Keep the original inputs in the downloaded record.
Add irregular sections
Split an irregular outline into shapes you can measure. Add their areas and subtract a cutout only once. Mark boundaries on a sketch before adding the numbers. An L-shaped pool can often be split into two rectangles. A curved section may need a measured area from a reliable plan.
Do not apply a fixed percentage to every kidney shape. Two pools with the same maximum length and width can have quite different areas. Enter a known measured surface area when a few simple sections do not describe the outline well.
Surface area is not liner area
The surface is the flat water-air boundary. Wall area depends on perimeter and water depth. A sloped floor has a different finish area from its horizontal plan area. Seams, overlaps and the liner maker's fitting method are also outside this tool.
For gallons, take this result to the volume calculator and add a measured average depth. For a sloping floor, use separate volumes when the slope changes. The heater calculator uses surface area only in loss modes that call for it.
Check units before saving
One metre equals about 3.28084 feet, so one square metre is about 10.7639 square feet. Area conversion squares the length factor. Multiplying by the length factor only would understate the square-foot result.
These conversions follow NIST measurement tables. The Sta-Rite engineering manual, printed page 2 shows how to add pool sections to find water volume.
FAQ
Does water depth change surface area?
Depth is not an input for the ideal outline formulas. A pool with sloped sides can have a different waterline outline at a different fill level, though. Measure at the water level used for your estimate. Do not use surface area as a substitute for average depth.
Can I use this to order a cover?
It gives a water-area estimate. A cover may need overlap, anchor points or a custom outline. Follow the cover maker's steps when you measure for an order. Mark steps, rails and raised features on that plan too. Area alone cannot prove that a cover will fit.
Related calculations and owner guides
Verdict on pool calculator area
Use the square footage of pool calculator for the exposed water surface. Save the outline and dimensions with the answer, then use the pool pump size calculator only after volume is known. Formula version 1.0 keeps the area calculation separate from equipment fit.