Pool Volume Calculator
Our pool volume calculator helps you determine the exact water volume of any swimming pool — rectangular, round, oval, or freeform — in cubic metres, litres, and US gallons. Knowing your pool volume is essential for correct chemical dosing, pump sizing, and water heating calculations. Simply enter the pool dimensions and depth to instantly see all three volume measurements, plus estimated weekly chemical quantities.
Accurate chemical dosing depends entirely on water volume. Under-dosing chlorine allows algae and bacteria to grow; over-dosing wastes money and can irritate swimmers. As a general rule, maintain free chlorine at 1–3 ppm, pH at 7.2–7.6, and alkalinity at 80–120 ppm. Weekly shock treatment (superchlorination) is recommended to oxidise organic compounds and prevent chloramine buildup. Always add chemicals to water, never water to chemicals, and wait at least 15 minutes between adding different products.
Frequently Asked Questions
How do I calculate pool volume?
Rectangular pool: Volume = Length × Width × Average Depth. Round pool: Volume = π × r² × Depth (where r = radius). Oval pool: Volume = π/4 × Length × Width × Depth. Freeform: use 0.85 as a correction factor on the bounding rectangle. The calculator handles all these formulas automatically.
How much chlorine does my pool need per week?
A general guideline is 175g of granular chlorine per 10,000 litres per week for maintenance dosing. Adjust based on: sunlight exposure (UV destroys chlorine — use stabilised chlorine or add cyanuric acid), bather load (more swimmers = more organic matter), water temperature (higher temp = faster chlorine consumption), and rainfall (dilutes and disrupts balance).
What is the ideal pool pH?
Ideal pool pH is 7.2–7.6. Below 7.0: water becomes acidic, irritates eyes and skin, corrodes metal fittings, and degrades pool surfaces. Above 7.8: chlorine becomes ineffective (at pH 8.0, only 3% of chlorine is active vs 73% at pH 7.0), water becomes cloudy, scale builds up. Test pH at least twice per week.
How often should I shock my pool?
Shock treatment (superchlorination) should be done: weekly during summer, after heavy rain, after a pool party (>10 bathers), when water becomes cloudy, or when chlorine demand is unusually high. Use 3–5× the normal chlorine dose. Shock in the evening and wait 24 hours before swimming.
What is the difference between pool chlorine and shock?
Regular chlorine maintains a steady 1–3 ppm free chlorine level. Shock (superchlorination) temporarily raises chlorine to 10–20 ppm to break down combined chlorines (chloramines) and oxidise organic matter. Chloramines cause the characteristic "swimming pool smell" and eye irritation — they indicate insufficient sanitisation, not too much chlorine.
How long does it take to fill a pool?
Fill time = Volume ÷ Flow rate. A typical garden hose flows at 15–20 litres/minute. A 50,000-litre pool: 50,000 ÷ 17 = ~49 hours (2 days) with one hose. Filling from a municipal supply also incurs water costs — factor this into installation budgets (typical: €0.003–0.006/litre).
How do I winterise my pool?
Winterising steps: 1) Lower water level below skimmer; 2) Shock and algaecide dose; 3) Balance pH and alkalinity; 4) Drain pump, filter, and heater completely; 5) Add winter cover; 6) Check monthly. In climates below −10°C, drain all plumbing fully to prevent freeze damage. Proper winterisation prevents costly spring damage.
What is alkalinity and why does it matter?
Total alkalinity (TA) acts as a pH buffer — it prevents pH from swinging rapidly. Ideal range: 80–120 ppm. Low TA causes pH to fluctuate wildly ("pH bounce"). High TA makes pH difficult to adjust and can cause scale. Raise TA with sodium bicarbonate (baking soda); lower it with muriatic acid added slowly.
How does cyanuric acid stabilise chlorine?
Cyanuric acid (CYA or stabiliser/conditioner) protects chlorine from UV degradation. Without CYA, direct sunlight destroys 50–90% of chlorine in 2 hours. With CYA at 30–50 ppm, chlorine lasts 5–10× longer. However, high CYA (>80 ppm) reduces chlorine effectiveness — this is called "chlorine lock." Ideal CYA: 30–50 ppm.
How do I reduce pool water evaporation?
Pool covers (solar or liquid) are the most effective method — they reduce evaporation by 90–95%. An uncovered 50m² pool loses approximately 100–200 litres per day in summer. Windbreaks, trees providing morning shade (without dropping leaves), and lowering water temperature all help. Each 10°C reduction in water temperature reduces evaporation by ~40%.
What size pool pump do I need?
The pump should circulate the full pool volume in 6–8 hours. For a 50,000-litre pool: 50,000 ÷ 7h ÷ 60min = ~120 litres/minute (7.2 m³/h). Select a pump with flow rate of 120–150 L/min for this pool. Variable speed pumps reduce energy costs by 60–80% compared to single-speed models — highly recommended for pools used >3 months per year.