// multi-utility computation suite · offline · instant · precise
┌──────────────────────────┐
│ [c] calcalyst_ │
│ computation suite │
└──────────────────────────┘
// select a module to initialize
/ search↵ open firstesc close
// adsenseEMPTY_LEADER_SLOT728×90
// adsenseMOBILE_ANCHOR_SLOT320×50
// keyboard_shortcuts
/focus search
↑↓navigate module list
Enter
open first result from search
open highlighted
compute when module is open
compute when focused in a field
Escclose module · clear selection
⌫
food.evapotranspiration-penman Calculator
Calculates reference evapotranspiration (ETo) using the FAO Penman-Monteith equation from temperature, humidity, wind speed, and solar radiation. ETo is the foundation of all scientific irrigation scheduling — it tells you how much water the crop needs without knowing the crop.
Inputs
Net Radiation Mj M2 Day
Reference formula or conversion factor shown for context.
Temperature C
Thermal state of the substance. Check whether the formula needs Celsius, Fahrenheit, or Kelvin (K = °C + 273.15).
Wind Speed M S
Vertical measurement. For health calculators, typically standing height without shoes.
Vapor Pressure Deficit Kpa
Force per unit area (Pa). Atmospheric pressure at sea level: 101,325 Pa. Check whether gauge or absolute pressure is required.
Results
reference ET₀ (mm/day)
Sample size or count used in the calculation.
Penman-Monteith ET₀ = ...
Sample size or count used in the calculation.
Δ (slope of saturation curve)
How close the system is to its capacity limit. Above 80% sustained saturation typically leads to queuing and latency spikes.
ET₀ for crop water (mm/season)
The value at the specified point or condition.
crop coefficient Kc
Sample size or count used in the calculation.
irrigation requirement
IRR (internal rate of return) -- the annualised return rate at which net present value equals zero. If IRR exceeds the hurdle rate, the investment adds value.