Pool Evaporation Rate Calculator

Plan top-ups and cover strategies by estimating how many liters evaporate from your pool each day. Combine surface area, water temperature, humidity, and wind to anticipate water usage and chemical balancing.

Multiply length by width for rectangular pools or use our Pool Volume calculator to approximate
Measure water temperature in the morning before sun and pumps change conditions
Use local weather data or a hygrometer near the pool surface
Estimate breeze speed at water level; even 1 m/s of airflow boosts evaporation

Examples

  • Family pool: 48 m² surface, 27°C water, 55% humidity, 2.0 m/s wind ⇒ 5,781 L/day
  • Compact plunge pool: 32 m² surface, 22°C water, 45% humidity, 1.2 m/s wind ⇒ 3,121 L/day

FAQ

Does this include splash-out or backwash losses?

No, it only models evaporation. Add those volumes separately for a full water budget.

Can I use Fahrenheit and mph?

Convert them first using the Fahrenheit to Celsius and Feet per Second to MPH calculators.

Will a solar cover change the result?

A cover greatly reduces evaporation; rerun the calculation with a lower effective wind speed (often 0.2–0.5 m/s) to approximate the benefit.

How often should I remeasure conditions?

Check humidity, temperature, and wind weekly during swimming season—weather swings can double or halve evaporation rates.

Additional Information

  • Formula adapted from empirical ASHRAE evaporation correlations for outdoor pools under light wind conditions.
  • Installing a solar or thermal cover overnight can reduce evaporation by 50–70%; plug the reduced wind speed into this calculator to model the benefit.
  • Pair the output with the Water Efficiency Savings calculator to understand cost and sustainability impacts of refilling.
  • Consider water chemistry: topping up changes hardness and sanitizer levels, so track losses alongside your maintenance log.

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