Air & leaves
VPD Lab.
VPD & Dew Point Calculator for Plants
Explore the relationship between air temperature, relative humidity and leaf temperature. See how air VPD differs from the leaf-to-air vapour pressure difference.
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How to use VPD Lab
- Enter air temperature and relative humidity from the same location and period.
- Enter a measured or explicitly assumed leaf temperature. It can differ from the air.
- Read the map as air VPD; the leaf result is calculated separately. Select any map cell to explore another temperature and humidity combination.
A worked example
At 25°C and 60% RH, air VPD is about 1.27 kPa. A cooler leaf changes the leaf-to-air vapour pressure difference even when the air readings stay the same.
Assumptions and scope
This is a saturation-over-water approximation from −30 to 60°C, not an ice or frost-point model. Crop, stage, airflow and measurement quality affect interpretation. A negative leaf result indicates potential condensation under the assumptions; it is not a disease diagnosis.
Primary method or data reference ↗
Results use the entered values and the method described here. Keep units, sampling conditions and the source of the data with your interpretation.