Leaf Transpiration Rate Calculator
Calculate leaf transpiration rate from stomatal conductance, leaf temperature, and relative humidity.
Get results in mol/m²/s and mm/day for plant physiology studies.
Transpiration Rate Transpiration is driven by the vapor pressure difference between the leaf interior and the air.
E = gs × VPD / P
Where:
- E = transpiration rate (mol H2O/m²/s)
- gs = stomatal conductance (mol H2O/m²/s)
- VPD = vapor pressure deficit between leaf and air (kPa)
- P = atmospheric pressure (kPa)
Vapor Pressure Deficit (VPD) VPD = es(Tleaf) × (1 - RH/100)
Where es is the saturation vapor pressure at leaf temperature: es = 0.6108 × exp(17.27 × T / (T + 237.3)) kPa
Stomatal Conductance (gs)
- Closed stomata: ~0.01 mol/m²/s
- Slightly open: 0.05–0.10
- Well-watered, moderate light: 0.15–0.30
- Fully open, wet soil: 0.30–0.45 mol/m²/s
Converting to mm/day E_mm = E × 18 × 86,400 / (1000 × density_water) ≈ E × 1.555 mm/day (18 g/mol = molar mass of water; 86,400 s/day; water density 1000 g/L)
Water Use Efficiency (WUE) WUE = carbon fixed (A) / water lost (E) A higher WUE means more carbon gained per unit of water lost — critical in drought conditions.