Pool Evaporation Loss
Calculator
Results
- Evaporation loss (L/day)
- 250
- Total water lost (L)
- 7,500
- Total water lost (m³)
- 7.5
- Heat lost to evaporation (kWh)
- 4,708.333333
Pool and aquarium results
| Evaporation loss (L/day) | 250 |
| Total water lost (L) | 7,500 |
| Total water lost (m³) | 7.5 |
| Heat lost to evaporation (kWh) | 4,708.333333 |
formula-map diagram
- Evaporation loss (L/day)
- 250
- Total water lost (L)
- 7,500
- Total water lost (m³)
- 7.5
- Heat lost to evaporation (kWh)
- 4,708.333333
Pool and aquarium relationship
Formula
loss (L/day) = area(m²) × rate(mm/day); 1 mm over 1 m² = 1 L= 250
Note
This is a simplified model: it applies a standard geometric or physical formula to the numbers you entered. Volumes assume a regular shape and an even average depth, and the kidney shape uses the common 0.45 × (A + B) × L area approximation. Chemical doses convert a target change into a product mass using the strength or label dose you enter, because the amount of active ingredient varies from product to product; they ignore pH, temperature, buffering, sunlight, bather load and existing chemical interactions. Heating uses Q = m × c × ΔT with c = 4186 J/kg·K and ignores heat losses to air, ground and evaporation; evaporation and cover figures use the rate you enter, not local weather. Aquarium stocking by surface area is a rule of thumb, not a biological limit. Always follow the product label and test the water before and after dosing, and consult a pool or aquarium professional for anything you are unsure about.
More in Pool and aquarium
See all →Frequently asked questions
What factors actually drive pool evaporation, and which ones does the calculator use?+
Evaporation depends mainly on surface area, the difference between water temperature and air temperature, relative humidity, and wind speed across the water surface. Warmer water, drier air, and more wind all accelerate evaporation, which is why the calculator asks for these conditions rather than giving a single fixed rate.
Why does evaporation depend on surface area and not on pool volume or depth?+
Evaporation is a surface phenomenon — molecules leave from the water's exposed top layer, so a shallow, wide pool loses water faster relative to its volume than a deep, narrow one with the same surface area. Two pools with identical surface area lose roughly the same amount of water to evaporation per day regardless of how deep either one is.
Why does my pool lose noticeably more water on windy or dry days?+
Wind continuously replaces the humid air layer just above the water with drier air, maintaining a steeper humidity gradient that speeds up evaporation, and low ambient humidity has the same effect by keeping the air 'thirstier' for moisture. Both factors are amplified further when the water is significantly warmer than the surrounding air, such as with a heated pool in cool weather.
How much of my pool's water loss is evaporation versus a leak?+
As a rough benchmark, typical evaporation is about 1/4 to 3/8 inch (roughly 6-10 mm) of water level per day under moderate conditions, more in hot, dry, windy climates or with heated pools. If your pool is losing noticeably more than this calculator's estimate, especially with the pump off, that gap points toward a leak rather than evaporation.
Why is a heated pool's evaporation loss so much higher than an unheated one?+
Evaporation rate increases sharply as the temperature difference between water and air grows, so a heated pool sitting well above ambient air temperature — especially on cool evenings — can evaporate two to three times faster than an unheated pool at ambient temperature. This is also why heated pools benefit disproportionately from a cover, which directly targets this larger heat and moisture loss.