VPD Calculator
Determine vapor pressure deficit (kPa) to optimize greenhouse climate and plant transpiration rates.
Instructions
Measure temperatures
Use infrared thermometers or sensors for air and leaf canopy temperatures.
Track humidity
Read relative humidity from a calibrated hygrometer inside the grow space.
Compare to crop targets
Maintain VPD within crop-specific ranges to balance transpiration and stomatal health.
Formula
es = 0.6108 × exp(17.27×T ÷ (T + 237.3))
ea = esair × RH%
VPD = esair − ea
Leaf VPD = esleaf − ea
Temperatures are in °C and vapor pressures in kPa. Use leaf temperature to refine canopy transpiration estimates.
About This Tool
Vapor pressure deficit (VPD) combines temperature and humidity to describe the drying power of air. Maintaining optimal VPD improves nutrient uptake, reduces mildew, and controls transpiration rates in controlled environments.
Integrate VPD monitoring with environmental controls for lighting, CO₂ injection, and irrigation to achieve consistent crop performance.
Common Questions
What VPD range should I target?
Vegetative stages often prefer 0.8–1.1 kPa; flowering crops thrive near 1.2–1.5 kPa. Adjust for species and growth stage.
Why use leaf temperature?
Leaves can be cooler than air due to transpiration. Leaf VPD guides irrigation and misting decisions more accurately.
How do lights affect VPD?
High-intensity lighting raises leaf temperature and VPD. Increase humidity or reduce temperature to stay within range.
Can I input Fahrenheit?
Convert to Celsius first (°C = (°F − 32) × 5⁄9) for accurate calculations.