How many litres is my pool? Working out pool volume
Length × width × average depth in metres, × 1,000, gives litres. An 8 m × 4 m pool averaging 1.4 m deep holds about 44,800 L. Formulas for every shape.
By NZ Swimming Pools
Key takeaways
- Rectangular pool: length × width × average depth (all in metres) × 1,000 = litres.
- Average depth is the shallow end plus the deep end, halved.
- Round pool: 3.14 × radius × radius × average depth × 1,000. Oval: length × width × average depth × 0.785 × 1,000.
- Worked example: 8 m × 4 m × 1.4 m average = 44.8 m³, or about 44,800 litres.
- Measure the water, not the coping, and use your real numbers: every chemical dose on a product label is per volume of water.
Multiply your pool's length by its width by its average depth, all in metres, then multiply by 1,000 to get litres. An 8 m × 4 m pool with a shallow end of 1.0 m and a deep end of 1.8 m averages 1.4 m deep, so it holds 8 × 4 × 1.4 = 44.8 m³, or about 44,800 litres.
How do I work out the volume of a rectangular pool?
Length × width × average depth gives cubic metres, and each cubic metre is 1,000 litres. Measure the water surface rather than the outside edge of the coping, which can add a surprising amount on a small pool. For a constant-depth pool, the average depth is just the depth.
- Measure the length and width of the water, in metres.
- Measure the depth at the shallow end and at the deep end, add them together and halve the total.
- Multiply length × width × average depth to get cubic metres (m³).
- Multiply by 1,000 to get litres.
What about round, oval and kidney-shaped pools?
Use the formula for the closest shape. These are the standard geometry formulas, so they give a good working figure. Freeform and kidney pools are irregular, so treat any formula as an estimate and, if precision matters, split the pool into simpler shapes and add them up.
| Shape | Formula | Example |
|---|---|---|
| Rectangle | Length × width × average depth × 1,000 | 8 × 4 × 1.4 × 1,000 = 44,800 L |
| Round | 3.14 × radius × radius × average depth × 1,000 | 4 m across (2 m radius), 1.2 m deep: about 15,070 L |
| Oval | Length × width × average depth × 0.785 × 1,000 | 7 × 3.5 × 1.3 × 0.785 × 1,000: about 25,000 L |
| Kidney or freeform | Average width × length × average depth × 1,000 | An estimate: split it into shapes for a closer figure |
How many litres are common pool sizes?
Here are some sizes worked through with the rectangle formula. They are arithmetic, not product specifications: a real shell's volume depends on its exact profile, steps and benches, which take up water, so check the builder's or manufacturer's stated volume when you have it.
| Size (water surface) | Average depth | Volume |
|---|---|---|
| 6 m × 3 m | 1.4 m | about 25,200 L |
| 7 m × 3.5 m | 1.4 m | about 34,300 L |
| 8 m × 4 m | 1.4 m | about 44,800 L |
| 10 m × 4 m | 1.5 m | about 60,000 L |
| 12 m × 5 m | 1.5 m | about 90,000 L |
Why does pool volume matter?
Almost everything you put in a pool is dosed per volume of water: salt, chlorine, pH adjusters, stabiliser and algaecide. Every product label gives its dose that way, so a guessed volume means every dose is guessed too. Volume also sizes the filter and pump, decides how long the pump needs to run to turn the water over, and drives what it costs to heat.
- Chemical doses: follow the product's label, using your real volume. Our water testing guide covers what to read before you add anything.
- Pump and filter: a bigger volume needs a pump and filter sized to move it through in a reasonable time.
- Heating: more water takes more energy to warm. See how to heat a pool in NZ.
- Filling: if you're on town supply, the water is metered. A truck delivery is usually priced by the load, so the volume tells you how many loads to book.
What does a pool this size cost to build?
CheckMyBuilder puts a standard 8 m × 4 m fibreglass pool at $35,000–60,000 installed on a straightforward site, and sprayed concrete at $80,000–160,000 (June 2026, excluding GST). Our pool cost calculator works through your own size, type and site, and the fibreglass vs concrete guide compares the two.
Questions
How do I calculate how many litres are in my pool?
Length × width × average depth in metres gives cubic metres. Multiply by 1,000 for litres. Average depth is the shallow end plus the deep end, halved.
How many litres is an 8 × 4 pool?
At an average depth of 1.4 m, about 44,800 litres (8 × 4 × 1.4 = 44.8 m³). A shallower or deeper profile changes that, so measure yours.
How do I work out the volume of a round pool?
3.14 × radius × radius × average depth × 1,000. A 4 m round pool (2 m radius) at 1.2 m deep holds about 15,070 litres.
How do I find the average depth of a sloping pool?
Measure the shallow end and the deep end, add them and halve the total. For a pool with a sudden drop rather than an even slope, work out each section separately and add them.
Why does the volume on the manufacturer's spec differ from my calculation?
Steps, benches, rounded corners and the shell profile all take up space. The manufacturer's stated volume is usually the better figure for a specific shell.
How many cubic metres is 50,000 litres?
50 m³. One cubic metre holds 1,000 litres.
Published 9 October 2026, last updated 9 October 2026 by NZ Swimming Pools. Every figure and rule on this page is quoted from a source we read in full on the checked date. See our editorial policy.