Weather & air
Vapour pressure deficit
Compare air and leaf saturation pressure with actual air moisture.
A clear answer. Here’s how.
Calculates actual air vapour pressure from relative humidity and the NWS over-water saturation equation. Air VPD = es(air)−actual; leaf-to-air vapour pressure difference = es(leaf)−actual. Reports kPa. A negative leaf difference means air vapour pressure exceeds saturation at that leaf temperature; no plant-specific target range or growing recommendation is selected.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Air temperature (°C)
- 25
- Leaf temperature (°C)
- 25
- Air relative humidity (%)
- 60
Example result
- Air VPD (kPa)
- 1.26745208015
- Leaf-to-air pressure difference (kPa)
- 1.26745208015
- Actual air vapour pressure (kPa)
- 1.90117812022
No plant-specific target range is inferred.