Pool volume calculator
Every pool chemical is dosed per cubic metre of water, so the volume is the first number to know. The calculator gives it in m³ and litres, plus the shock chlorine for the dose on your product.
Your measurements
From the product label.
Result
- Water volume
- 25.2 m³
- In litres
- 25,200 L
- Shock chlorine (first treatment)
- 378 g
Chlorine needs vary with the treatment (chlorine, bromine, salt) — follow the manufacturer's instructions.
How the calculation works
- Volume (m³) = length × width × average depth.
- Shock chlorine (g) = volume × dose from the label (g/m³).
Worked example
A 6 × 3 m pool with an average depth of 1.4 m holds 6 × 3 × 1.4 = 25.2 m³ of water. At a shock dose of 15 g/m³ you need about 380 g of granular chlorine.
What the calculator assumes
- 15 g/m³ is typical for granular shock chlorine (55–65% available chlorine) at first fill or after heavy rain; daily maintenance is 1.5–3 g/m³.
- For pools with a sloping floor, the average depth is the mean of the shallow and deep ends.
When to adjust the result
- The exact dose is the one on your product's label; slow tablets and liquid chlorine are dosed differently.
- Chlorine works well only at a pH of 7.2–7.6 — correct the pH first.
- For filtration, all the water should pass through the filter several times a day — the pump is chosen by volume.
Using the pool volume correctly
Almost every pool calculation starts from the volume: chemical doses, pump size and heating time. Measure the average depth — for a sloping floor, take the shallow and deep ends and average them — and use the real water level, usually a few centimetres below the edge.
The filtration pump should turn over the full volume in about 6–8 hours, so divide the volume by that time to get the minimum flow. Test the water before dosing rather than adding chemicals on a schedule, and add them in small steps with the pump running. Always follow the dosing instructions on the product label.
Frequently asked questions
How do I calculate pool volume?
Length × width × average depth gives cubic metres; multiply by 1,000 for litres.
How much chlorine for a pool?
Follow the product label; a typical granular shock dose is around 10–20 g per m³, and maintenance 1.5–3 g per m³ per day.
How do I calculate an oval pool's volume?
Length × width × average depth × about 0.89 gives a close approximation; a round pool is 3.14 × radius² × depth.
How big a pump does my pool need?
One that filters the whole volume in about 6–8 hours: for 40 m³ that is roughly 5–7 m³/h at the pressure of your filter system.