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Calcimator

Evapotranspiration Calculator

Estimate reference evapotranspiration (ET₀) using a simplified Penman-Monteith approach from temperature, humidity, wind speed, and solar radiation.

Inputs

°C
%
m/s
MJ/m²/day

Results

Daily ET₀

5.16 mm/day

Weekly ET₀

36.1 mm/week

Monthly ET₀154.7 mm/month
Annual ET₀ (est.)1,882 mm/yr
Hargreaves ET (check)4.71 mm/day
Vapor Pressure Deficit1.584 kPa
Water Requirement5.16 L/m²/day
How to Use This Calculator
  1. Enter Mean Temperature, Relative Humidity, and Wind Speed.
  2. Set Solar Radiation.
  3. Review Daily ET₀ (mm/day) and Weekly ET₀ (mm/week).
  4. Use Monthly ET₀ (mm/month) and Annual ET₀ (est.) (mm/yr) to inform your decision.
  5. Use the chart to visualize the results and explore different scenarios by adjusting inputs.
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Formula

ET₀ = [0.408ΔRn + γ(900/(T+273))u₂(es-ea)] / [Δ + γ(1+0.34u₂)]

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