Pool Volume Calculator
Calculate how much water your swimming pool holds — essential for dosing chemicals correctly and estimating filling cost. Works for rectangular, round and oval pools using the average depth.
How to use this calculator
- Choose the pool shape and enter its length/diameter (and width).
- Enter the shallow and deep-end depths — use the same value for a flat bottom.
- Press Calculate for litres and gallons, plus a rough fill cost.
Formula used
Surface area depends on shape: length × width (rectangular), π × radius² (round), or π × (½length) × (½width) (oval). Average depth is the mean of the shallow and deep ends for a linearly sloping floor.
Example calculation
An 8 m × 4 m rectangular pool, 1.2 m shallow to 2.0 m deep: surface 32 m², average depth 1.6 m → 51.2 m³ = 51,200 litres.
That's about 13,500 US gallons — the number every chemical dosing table needs.
Why pool volume is the key number
Almost everything about pool maintenance is dosed by volume: chlorine, pH adjusters, algaecide and shock treatments all specify an amount per thousand litres or gallons. Get the volume wrong and you either under-treat (cloudy, unsafe water) or over-treat (wasted chemicals, irritation, damage) — so the litre figure here is genuinely load-bearing for pool care.
The one subtlety is depth. Pools with a sloping floor don't have a single depth, so you use the average of the shallow and deep ends — valid because the floor slopes linearly. For pools with a sharp "hopper" deep section the true volume is slightly less than this average gives, but for most residential pools the shallow/deep average is accurate enough for dosing.
Why use this calculator?
- Get the exact litre/gallon figure that chemical dosing depends on.
- Handles rectangular, round and oval shapes.
- Averages sloped-floor depths correctly.
Frequently asked questions
How many litres in my pool?
Multiply the surface area by the average depth, then by 1,000. An 8×4 m pool averaging 1.6 m deep holds 8×4×1.6 = 51.2 m³ = 51,200 litres. Enter your dimensions above for any shape.
How do I find the volume of a pool with a deep end?
Use the average of the shallow and deep-end depths as the depth in the calculation — valid for a floor that slopes evenly. For pools with a small, steep deep section, the real volume is a little less.
Why do I need my pool's volume?
Every pool chemical is dosed per unit of water, so accurate volume prevents both under-dosing (unsafe, cloudy water) and over-dosing (wasted product and possible irritation). It also lets you estimate the cost and time to fill.