VPD Calculator
Calculate Vapor Pressure Deficit for optimal plant growing conditions and transpiration control
Calculate Vapor Pressure Deficit
Ambient air temperature in growing environment
Typically 1-3°C cooler than air due to evapotranspiration
Percentage of moisture in air (0-100%)
General purpose range
VPD Calculation Results
Generic Crop Assessment
VPD Unit Conversions
Vapor Pressure Breakdown
Calculation Formulas
Example Calculation
Greenhouse Conditions
Air temperature: 22°C (72°F)
Relative humidity: 55%
Canopy temperature: 20°C (68°F)
Calculation Steps
1. Leaf vapor pressure = 0.61078 × exp[17.27 × 20 / (20 + 237.3)] = 2.338 kPa
2. Air saturation pressure = 0.61078 × exp[17.27 × 22 / (22 + 237.3)] = 2.644 kPa
3. Actual air pressure = 2.644 × 0.55 = 1.454 kPa
4. VPD = 2.338 - 1.454 = 0.88 kPa
VPD Ranges by Crop
VPD Interpretation
VPD Management Tips
Use humidifiers to increase humidity when VPD is too high
Increase ventilation to reduce humidity when VPD is too low
Monitor leaf temperature with infrared thermometers
Adjust lighting intensity to control canopy temperature
Lower VPD during early growth stages
Understanding Vapor Pressure Deficit (VPD)
What is VPD?
Vapor Pressure Deficit (VPD) is the difference between the amount of moisture in the air and the maximum moisture the air can hold at a given temperature. It's a key environmental factor that affects plant transpiration and growth.
Why VPD Matters:
- • Controls rate of plant transpiration
- • Affects nutrient uptake through roots
- • Influences stomatal behavior
- • Determines plant stress levels
- • More accurate than relative humidity alone
VPD vs Relative Humidity
Relative Humidity
Temperature-dependent measure. 60% RH at different temperatures feels very different.
Vapor Pressure Deficit
Absolute measure of "drying power" of air. Same VPD feels similar regardless of temperature.
VPD Effects on Plant Growth
Low VPD (< 0.5 kPa)
High humidity conditions:
- • Slow transpiration rate
- • Reduced nutrient uptake
- • Higher disease risk
- • Good for young plants
Optimal VPD (0.5-1.2 kPa)
Balanced conditions:
- • Healthy transpiration
- • Good nutrient flow
- • Active photosynthesis
- • Vigorous growth
High VPD (> 1.5 kPa)
Low humidity conditions:
- • Excessive transpiration
- • Water stress
- • Stomata closure
- • Reduced growth
Calculation Methods
Tetens Equation
The standard formula for calculating saturation vapor pressure:
Where T is temperature in °C and SVP is in kPa
VPD Formula
The vapor pressure deficit calculation:
Difference between leaf and air vapor pressures