Pool Volume Calculator

How this is calculated

Volume is surface area multiplied by average depth. The surface area depends on the shape: a rectangle is length x width, and a circle or an oval is length x width x pi/4, which is about 0.7854. A round pool is just the case where length and width are both the diameter, so the same factor covers round and oval together. The average depth is the shallow end plus the deep end, divided by two. That is exact for a floor that slopes evenly from one to the other, which is the common case. It is NOT exact for a pool with a flat shallow area, then a sudden drop, then a flat deep area - a very common shape in older pools. That layout holds less water than an even slope of the same two depths, so the figure here will read slightly high. If your pool has a distinct hopper or diving well, measure the flat sections separately and add them. Cubic feet become US gallons by multiplying by 7.480519. That figure is exact by definition, not an approximation: a US gallon is defined as 231 cubic inches and a cubic foot is 1728, and 1728 divided by 231 is 7.480519. The surface area is reported separately because several things are sized by area rather than volume - covers, solar rings, and the run time some pumps and heaters are specified against. Get this number once and write it down somewhere permanent. Every chemical dose on every label is per volume, so an error here is repeated into every dose you ever make, in the same direction, forever. Being wrong by a fifth on the volume means being wrong by a fifth on every bag of shock for as long as you own the pool.

Common questions

My pool is round. What do I enter?

The diameter in both the length and the width boxes, with the shape set to round. A circle is the case of an ellipse where both axes are the same, so the same pi/4 factor handles round and oval together - there is no separate calculation for them. For an oval, use the long axis as the length and the short axis as the width.

How do I handle a flat shallow area and a separate deep end?

Measure them separately and add the results. Averaging the two depths assumes the floor slopes evenly the whole way, which is true of many pools and not of the ones with a flat shallow section, a sudden drop and a flat deep well. That layout holds LESS water than an even slope between the same two depths, so a single calculation will read high. Run the calculator once per section and add the gallons.

Why does the exact volume matter so much?

Because every chemical dose you will ever measure is written per volume. An error here does not stay put - it is repeated into every dose, in the same direction, for as long as you own the pool. Being twenty percent out means being twenty percent out on every bag of shock, every jug of acid and every calculation of turnover, indefinitely. It is worth ten minutes with a tape measure once.

Is 7.48 gallons per cubic foot exact?

It is exact, and the calculator uses more of it than most: 7.480519. It is not a measured constant but a consequence of definitions - a US gallon is exactly 231 cubic inches and a cubic foot is exactly 1728, so the conversion is 1728 divided by 231. Note this is the US gallon; an imperial gallon is a different and larger unit, so a product dosed in imperial gallons needs converting.

Should I measure the water level or the wall height?

The water. Depth means the depth of the water, not the height of the pool wall - there is usually four to eight inches of freeboard above the waterline, and counting it inflates the volume by several percent on a shallow pool. Measure from the floor to where the water actually sits.

What is the surface area figure for?

Covers, solar rings and some equipment sizing are specified by area rather than volume, and evaporation depends on surface rather than depth too. It is also a quick sanity check on your own measurements - if the area does not look like the pool you are standing next to, one of the numbers you entered is wrong.

Take it further with AI

Copy this into ChatGPT or Claude with your own numbers filled in. It hands over the figures this calculator worked out, so the answer is built on real arithmetic instead of a guess.

I used the Pool Volume Calculator at https://www.bfcbrilliance.com/tools/pool-volume-calculator.

What I entered:
- Shape: ___
- Length (ft): ___
- Width (ft): ___
- Shallow end depth (ft): ___
- Deep end depth (ft): ___

What it calculated:
- Your pool holds: ___
- Cubic feet: ___
- Average depth: ___
- Surface area: ___
- In litres: ___

Use those figures as given — they are already worked out, so please don't recalculate or estimate your own. Help me turn them into a plan: what to buy or do, in what order, roughly what it should cost, and the mistakes people most often make with this job.

Where the job touches structure, gas, or electrics, tell me to check local building code and whether a permit or a licensed trade is required.

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