How to use the vapor pressure deficit calculator
Find how far air is from saturation, which drives plant water loss and drying. Enter air temperature, relative humidity in the fields above; the saturation vapor pressure, vapor pressure deficit are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “vapour pressure deficit”, “plant transpiration driving force”, “how dry is the air”, “calculate vapor pressure deficit”, “find saturation vapor pressure”.
Formula
Variables
- T — Air temperature (°C)
- RH — Relative humidity (%)
Worked example
With air temperature = 30 °C, relative humidity = 50 %, the calculator gives saturation vapor pressure ≈ 4.243065 kPa; vapor pressure deficit ≈ 2.121533 kPa.
Frequently asked questions
What is the vapor pressure deficit calculator used for?
Find how far air is from saturation, which drives plant water loss and drying. It helps with questions such as “vapour pressure deficit”, “plant transpiration driving force”, “how dry is the air”.
What is the formula for the vapor pressure deficit calculation?
Saturation vapor pressure (kPa) = 0.6108 × exp(17.27 × T / (T+237.3)). Vapor pressure deficit (kPa) = [Saturation vapor pressure] × (1-RH / 100). Here T is air temperature (°C), RH is relative humidity (%).
What inputs do I need for the vapor pressure deficit calculator?
You need air temperature in °C, relative humidity in %. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the vapor pressure deficit calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the vapor pressure deficit result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.