How pool volume is calculated
Each pool shape uses a specific formula. For a rectangular pool: length × width × average depth. For a circular pool: π × radius² × depth. For an oval pool: π/4 × length × width × depth. For a kidney-shaped pool: (widest width + narrowest width) ÷ 2 × length × 0.89 × depth — the 0.89 factor accounts for the concave section.
The calculator uses average depth, not deep-end depth. Add your shallow-end depth and your deep-end depth together and divide by two. A pool that's 1.0 m at the shallow end and 2.0 m at the deep end has an average depth of 1.5 m.
Why does pool volume matter?
Every pool chemical product — chlorine, pH adjusters, algaecide, clarifier, salt — is dosed per 10,000 litres (10 kL). Getting your volume right means you're not under-dosing (leaving the pool unsafe) or over-dosing (wasting money and potentially causing irritation).
Your pool volume is also important for pump sizing and turnover rate. For good water quality, your pump should turn over the full pool volume every 6–8 hours. A 50,000 L pool needs a pump capable of at least 6,250 L/hr (6.25 kL/hr).
Common AU pool chemical dosing guide
- Granular chlorine (calcium hypochlorite 70%) — 170 g per 10,000 L to raise free chlorine by 1 ppm.
- Liquid chlorine (sodium hypochlorite 12.5%) — 800 mL per 10,000 L to raise free chlorine by 1 ppm.
- pH Up (sodium carbonate) — 100 g per 10,000 L to raise pH by 0.1.
- pH Down (sodium bisulphate) — 100 g per 10,000 L to lower pH by 0.1.
- Salt (for chlorinators) — 200 kg per 10,000 L to raise salinity by 1,000 ppm. Most AU chlorinators require 3,000–5,000 ppm.
- Stabiliser (cyanuric acid) — 90 g per 10,000 L to raise CYA by 10 ppm.
How often should I test my pool water?
Test free chlorine and pH at least twice a week during summer and weekly in winter. Use a good-quality test kit or take a water sample to your local pool shop — most will test it for free and advise on dosing. In QLD and northern NSW, the hot summer sun burns through chlorine faster; daily testing is sensible during heatwaves.