How to use the aridity index calculator
Find the aridity index from annual precipitation and potential evapotranspiration, and the climate class it implies. Enter annual precipitation, potential evapotranspiration in the fields above; the aridity index, climate class are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “aridity index”, “dryland classification”, “precipitation to PET ratio”, “calculate aridity index”, “find aridity index”.
Formula
Variables
- P — Annual precipitation (mm)
- PET — Potential evapotranspiration (mm)
Worked example
With annual precipitation = 500 mm, potential evapotranspiration = 1200 mm, the calculator gives aridity index ≈ 0.4166667; climate class ≈ Semi-arid text.
Frequently asked questions
What is the aridity index calculator used for?
Find the aridity index from annual precipitation and potential evapotranspiration, and the climate class it implies. It helps with questions such as “aridity index”, “dryland classification”, “precipitation to PET ratio”.
What is the formula for the aridity index calculation?
Aridity index = P / PET. Climate class (text) = [Aridity index]<0.05?"Hyper-arid":([Aridity index]<0.2?"Arid":([Aridity index]<0.5?"Semi-arid":"Sub-humid or humid")). Here P is annual precipitation (mm), PET is potential evapotranspiration (mm).
What inputs do I need for the aridity index calculator?
You need annual precipitation in mm, potential evapotranspiration in mm. 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 aridity index 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 aridity index 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.