Evaporation Rate Calculator

Your details

Switch all length, speed, and temperature inputs between metric and imperial.
The open water surface exposed to air (pool, pond, tank, slab, etc.).
m²
Measured at about 1 m (3 ft) above the water surface.
m/s
Dry-bulb air temperature measured in the shade near the surface.
°C
Ambient relative humidity of the air above the water.
%
Temperature at the water surface. Usually warmer than the air in summer and cooler in winter.
°C
Choose the unit for the evaporation rate output.
Evaporation rateHigh evaporation
11.395

Mass of water evaporated per unit time from the surface

Rate unitkg/h
Rate (kg/h)11.3954kg/h
Rate (L/day)273.49L/day
Xs (water surface)0.02383kg/kg
X (ambient air)0.00993kg/kg
Xs - X0.0139kg/kg
ACI concrete riskHIGH - precautions required (>= 1.0 kg/m²/h)
Rate per m²1.1395kg/m²/h
1.1395 kg/m²/h
Low<0.5Moderate0.5-1High1+

Evaporation rate: 11.395 kg/h from this surface.

  • Your surface loses about 11.395 kg/h (273.5 litres per day) to evaporation.
  • The humidity ratio difference (Xs - X) driving evaporation is 0.01390 kg/kg. Raising wind speed or lowering humidity increases this driving force.
  • The area-normalised rate exceeds 1.0 kg/m²/h, the ACI 305 threshold above which fresh concrete slabs are at high risk of plastic-shrinkage cracking. Erect windbreaks, apply evaporation retarder, or begin curing immediately.

Next stepTo reduce evaporation, lower wind exposure (windbreaks or covers), increase relative humidity (fogging), or shade the surface to reduce water temperature.

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