Brazil Pool Volume Calculator: Liters, Gallons, Chlorine and Filtration
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Nearly every pool problem starts with not knowing the volume, because every chemical label doses per 1,000 liters. Three tape-measure readings fix that. This calculator handles rectangular, round and oval pools, returns the volume in cubic meters and liters, and converts it into the numbers that matter weekly: maintenance chlorine, shock dose and how many hours a day the pump should run.
The volume formulas
One cubic meter equals 1,000 liters, so the volume in m³ is the number every product label speaks in. Rectangular and square pools: length × width × average depth. A common 8 m × 4 m × 1.40 m pool holds 44.8 m³, or 44,800 liters.
Round pools: π × radius² × average depth, where the radius is half the diameter. This is where most mistakes happen — entering the diameter as the radius (or the reverse) throws the volume out by a factor of four. A 4 m diameter pool at 1.20 m deep holds 15.08 m³, or 15,080 liters.
Oval pools: length × width × depth × 0.89. The factor accounts for the two rounded ends, which remove roughly 11% of the equivalent rectangle; it sits between a pure rectangle (1.00) and a true ellipse (π/4 = 0.785). Measure the water at the inner wall rather than the outer structure, and for a sloping floor average the shallow and deep ends.
Chlorine and pH dosing
Correct the pH first, then chlorinate. Chlorine loses most of its disinfecting power as pH climbs — at 8.0 less than a quarter of it works — which is why the target band is 7.2 to 7.6. Free chlorine should sit between 1 and 3 ppm; above 5 ppm nobody should be in the water.
Using granular chlorine at 65% available chlorine, weekly maintenance runs about 4 g per m³, raising roughly 2.6 ppm, ideally split across two or three applications. Shock chlorination takes about 15 g per m³, which lifts free chlorine to near 10 ppm. To raise pH by 0.2, soda ash dosed at roughly 15 g per m³; to lower it, about 6 ml per m³ of liquid pH reducer, repeated until the reading lands in range.
Dissolve granular chlorine in a bucket before adding it, since neat granules stain vinyl and fiberglass liners. Apply late in the day with the pump running, because midday sun destroys unstabilized free chlorine within hours. Multi-action 3-in-1 and 10-in-1 granules typically carry only 40–45% available chlorine, so their label dose differs from the figures here.
Filtration time and running costs
The minimum run time is one full turnover: volume divided by pump flow. A half-horsepower residential pump moves roughly 9 m³ per hour, so a 44.8 m³ pool turns over in about five hours. Add an hour or two of margin for heat, heavy bathing loads or a loaded filter, and you land on the 6 to 8 hours a day that residential pools generally need. Bigger pools need more — 75 m³ calls for about 9.5 hours.
Running costs below use Brazilian electricity rates in reais (R$). The pump, not the chemicals, dominates the monthly bill. At the September 2026 Brazilian residential average of R$0.95/kWh, a half-horsepower pump (368 W) running 6 hours a day costs R$62.93 a month, while a one-horsepower unit (735 W) costs R$125.69. Chemicals for the same pool add roughly R$50 to R$70. Cutting a one-horsepower pump from 10 hours to 6 saves about R$84 a month, more than the entire chemical budget.
Green water always means algae, and algae always means free chlorine sat at zero for too long. Recovery: brush the walls, set pH to 7.2, shock the pool, run the pump for 24 hours straight, apply algaecide the next day, vacuum the dead algae to waste rather than to the filter, then backwash.
Frequently asked questions
How many liters does my pool hold?
Multiply length × width × average depth in meters for cubic meters, then multiply by 1,000 for liters. An 8 m × 4 m × 1.40 m pool holds 44.8 m³, or 44,800 liters. Round pools use π × radius² × depth; oval pools take the rectangular result times 0.89.
How much chlorine does my pool need each week?
With granular chlorine at 65% available chlorine, about 4 g per m³ per week, which raises roughly 2.6 ppm and holds free chlorine in the 1–3 ppm target band. For a 44.8 m³ pool that is 179 g a week, best split across two or three doses.
What is the shock chlorination dose?
Roughly 15 g of 65% granular chlorine per m³, lifting free chlorine to about 10 ppm — 672 g for a 44.8 m³ pool. Do it late in the day with the pump running, filter for at least 8 hours straight, and wait until testing shows below 3 ppm before swimming.
How many hours a day should the pool pump run?
At least one full turnover: volume divided by pump flow, which is about 9 m³ per hour for a half-horsepower pump. Add one to two hours of margin, giving 6 to 8 hours a day for most residential pools and around 9.5 hours for a 75 m³ pool.
Sources
Reference estimate. Doses assume granular chlorine with 65% available chlorine and may not match your product: multi-action 3-in-1 and 10-in-1 granules typically contain 40–45%, and trichlor tablets follow a different application logic. Always follow the dosing table printed on the manufacturer label and verify with a test kit or strips — the correct dose also depends on temperature, sun exposure, bather load, total alkalinity and cyanuric acid level. The suggested filtration time assumes a pump flow of 9 m³/h; adjust for your actual pump and filter. Costs vary by region, brand and electricity tariff.
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Also available in Portuguese: Calculadora de piscina: volume em litros, cloro e tempo de filtragem