Vapor Pressure Deficit (VPD) Calculator

Calculate Vapor Pressure Deficit (VPD) — a critical environmental parameter for greenhouses, indoor gardens, and horticultural research.

Formula

SVP = 0.6108 × exp(17.27 × T / (T + 237.3))
AVP = SVP_air × RH/100
VPD_leaf = SVP_leaf − AVP

VPD Targets by Growth Stage

• Propagation / Clones: 0.4 – 0.8 kPa
• Early vegetation: 0.8 – 1.0 kPa
• Late veg / early flower: 1.0 – 1.2 kPa
• Mid-late flower: 1.2 – 1.6 kPa

Too low VPD (high RH) suppresses transpiration, slows nutrient uptake, and invites mildew. Too high VPD (low RH or hot leaves) closes stomata, causing wilting and stunted growth.