Pool Measurement Calculator
Measure a pool properly and every decision downstream gets easier. This pool measurement calculator takes pool length, width, shallow end depth, and deep end depth, then returns surface area (for solar cover sizing), perimeter (for waterline tile and coping), average depth (for heater sizing), volume in gallons (for chemicals), and wall surface area (for paint, plaster, or replacement liners). Works for rectangle, round, oval, and kidney pools.
Core Pool Measurements
Five measurements define a pool. A pool measurement calculator turns those five numbers into every derived figure you need:
- Length: longest dimension of the pool (or diameter for round pools).
- Width: shortest dimension, perpendicular to length.
- Shallow end depth: water depth at the shallow end.
- Deep end depth: water depth at the deep end (same as shallow if flat bottom).
- Shape: rectangle, round, oval, or kidney.
What the Pool Measurement Calculator Returns
| Output | Formula | Used For |
|---|---|---|
| Surface area | By shape: L x W, pi x r^2, pi x (L/2)(W/2) | Solar covers, chemical algaecide, heat loss |
| Perimeter | By shape: 2(L+W), pi x D, ellipse perimeter | Waterline tile, coping, fence |
| Average depth | (Shallow + Deep) / 2 | Heater sizing, chemical dosing |
| Volume (gallons) | Area x Avg Depth x 7.48 | All chemical dosing, heater BTU, pump GPM |
| Wall surface | Perimeter x Avg Depth | Plaster, paint, replacement liner |
How to Measure a Pool Accurately
Use a tape measure and always measure inside the pool, waterline to waterline. Including the coping or deck is the most common mistake and it overstates volume 10-20%. For vinyl liner pools, measure between the walls at the water level. For concrete and plaster pools, measure across the tile or plaster surface.
- Length and width: Stretch a tape across the longest and widest points. For freeform shapes, measure the bounding rectangle.
- Depth: A weighted string or a long stick works. Don't stand on the bottom; reach in from the side.
- Perimeter: For irregular pools, walk the edge with a surveyor's wheel or use a flexible tape around the waterline tile.
Pool Measurement Reference Chart
| Pool | Shape | Surface | Perimeter | Avg Depth | Volume |
|---|---|---|---|---|---|
| 16 x 32 ft | Rectangle | 512 sq ft | 96 ft | 5 ft | 19,150 gal |
| 18 x 36 ft | Rectangle | 648 sq ft | 108 ft | 5 ft | 24,250 gal |
| 20 x 40 ft | Rectangle | 800 sq ft | 120 ft | 5 ft | 29,900 gal |
| 24 ft | Round | 452 sq ft | 75 ft | 4.3 ft | 14,570 gal |
| 18 ft | Round | 254 sq ft | 57 ft | 4.3 ft | 8,180 gal |
| 15 x 30 ft | Oval | 353 sq ft | 72 ft | 4.3 ft | 11,380 gal |
Waterline Tile and Coping from Perimeter
The pool measurement calculator's perimeter output tells you how many linear feet of waterline tile and coping to order. Waterline tile comes in 6-inch strips, usually sold by the linear foot. A 20 x 40 ft rectangle pool has a 120 ft perimeter; at $10-20 per linear foot installed, waterline tile runs $1,200-2,400. Add 10% for cuts and corners.
Plaster or Replacement Liner from Wall Area
The pool measurement calculator returns wall surface area as perimeter x average depth. A 20 x 40 ft pool at 5 ft avg depth has 120 x 5 = 600 sq ft of wall surface, plus 800 sq ft of floor, for 1,400 total sq ft of finish. Plaster runs $4-7 per sq ft, so replastering a typical in-ground pool costs $5,600-9,800. Replacement vinyl liners price by pool shape and size, typically $1,500-3,500 for residential pools.