What this calculator does
Vapor pressure deficit (VPD) works out gap between saturation and actual vapor pressure, the driving force for plant transpiration. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
The inputs explained
| Field | What to enter |
|---|---|
| Leaf temperature (°C) | A number, measured in °C. Starts at 24. |
| Air temperature (°C) | A number, measured in °C. Starts at 22. |
| Relative humidity (%) | A number, measured in %. Starts at 60. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with leaf temperature
Every other input is held at the calculator’s starting values while leaf temperature varies. Select any row to load that scenario into the calculator.