Calculate hourly and daily evaporation with practical inputs. See results, graphs, and export options instantly. Useful for ponds, tanks, labs, farms, and field studies.
The page stays single column overall, while the input grid uses 3 columns on large screens, 2 on smaller screens, and 1 on mobile.
| Case | Area | Water Temp | Air Temp | RH | Wind | Hours | Depth Loss | Volume Loss | Mass Loss |
|---|---|---|---|---|---|---|---|---|---|
| Pond Example | 120.00 m2 | 29.00 °C | 24.00 °C | 50 % | 10.00 kmh | 24.00 | 22.485 mm | 2,698.181 L | 2,687.322 kg |
| Tank Example | 36.00 m2 | 32.00 °C | 28.00 °C | 45 % | 6.00 kmh | 12.00 | 7.568 mm | 272.447 L | 271.100 kg |
| Lab Tray Example | 18.00 ft2 | 27.00 °C | 25.00 °C | 60 % | 1.80 ms | 8.00 | 2.784 mm | 4.656 L | 4.640 kg |
These examples use the same logic as the calculator, so users can compare practical scenarios quickly.
This calculator uses a Meyer-style evaporation estimate with Tetens saturation vapor pressure and a temperature-based water density estimate.
1) Saturation vapor pressure
es(T) = 6.112 × exp[(17.67 × T) / (T + 243.5)]
where T is temperature in °C and pressure is in hPa.
2) Actual air vapor pressure
ea = es(Tair) × RH / 100
3) Vapor pressure deficit
VPD = max[es(Twater) − ea, 0]
4) Meyer evaporation estimate
E(mm/day) = C × (1 + U / 16) × VPD × Fexp
5) Volume and mass
Volume loss (L) = depth loss (mm) × area (m²)
Mass loss (kg) = volume (L) × water density (kg/L)
Meaning of symbols
This method is practical for screening, planning, and operations. It is not a substitute for detailed site calibration, energy-balance studies, or regulatory-grade evaporation measurement.
It estimates evaporation depth, volume loss, and mass loss from an exposed water surface using temperature, humidity, wind, area, and exposure settings.
Yes. It works well for practical estimates on ponds, tanks, trays, basins, and similar open surfaces when a quick engineering calculation is needed.
Wind removes moist air near the surface and replaces it with drier air. That raises mass transfer and usually increases evaporation rate.
Water temperature controls surface saturation pressure. Air temperature and humidity control the surrounding air moisture. The gap between them drives evaporation.
Use small or shallow water for many exposed operational surfaces. Use large or deep water for broader natural surfaces. Use custom when field calibration data exists.
High humidity reduces vapor pressure deficit. When the air is nearly saturated, evaporation drops and can become very small in the estimate.
They are estimated from the calculated volume loss and water density at the chosen water temperature. They are useful for planning, not laboratory certification.
Yes. After calculation, use the CSV button for spreadsheet-friendly output or the PDF button for a printable result snapshot.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.