Evapotranspiration Calculator
For a month averaging 25 °C with p = 0.27, Blaney–Criddle gives 5.3001 mm/day.
From FAO tables: about 0.27 at the equator, varying with latitude and month.
5.3001 mm/day
Full answer, then cut to fewer decimals (not rounded):
- 5.3001 mm/day
- 5.300 mm/day
- 5.30 mm/day
- 5.3 mm/day
- Crop evapotranspiration ETc = Kc ET₀
- 5.3001 mm/day
- Per 30-day month
- 159.003 mm
Step-by-step solution
- ET₀ = p (0.46 T + 8.13) = 0.27 × (0.46 × 25 + 8.13) = 5.3001 mm/day
Evapotranspiration Formula
ET₀ = p (0.46 T + 8.13)
Hargreaves: ET₀ = 0.0023 Ra (T_mean + 17.8)√(Tmax − Tmin); ETc = Kc ET₀
Worked Example
A month with a mean temperature of 25 °C and p = 0.27:
- ET₀ = p (0.46 T + 8.13) = 0.27 × (0.46 × 25 + 8.13) = 5.3001 mm/day
Per 30-day month: 159.003 mm
GATE tip
Ra must be in mm/day of evaporation: divide MJ/(m²·day) by 2.45.
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Frequently asked questions
Which method is most accurate?
FAO Penman–Monteith is the standard; Blaney–Criddle and Hargreaves are simpler estimates when only temperature data exist.
What is Kc?
The crop coefficient: the ratio of crop ET to reference grass ET, varying with crop and growth stage (about 0.3 to 1.2).
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
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APA
Scientific Converters. (2026, October 15). Evapotranspiration Calculator. Retrieved October 29, 2026, from https://scientificconverters.com/calculators/evapotranspiration-calculator/
IEEE
Scientific Converters, "Evapotranspiration Calculator," scientificconverters.com. Accessed: Oct. 29, 2026. [Online]. Available: https://scientificconverters.com/calculators/evapotranspiration-calculator/