Enter the annual precipitation and potential evapotranspiration into the calculator to determine the Aridity Index. This calculator can also evaluate any of the variables given the others are known.

## Aridity Index Formula

The following formula is used to calculate the Aridity Index.

AI = P / PET

Variables:

- AI is the Aridity Index
- P is the annual precipitation (mm)
- PET is the potential evapotranspiration (mm)

To calculate the Aridity Index, divide the annual precipitation by the potential evapotranspiration. The result is the Aridity Index, which is a measure of the dryness of the climate. A lower Aridity Index indicates a drier climate, while a higher Aridity Index indicates a wetter climate.

## What is an Aridity Index?

An Aridity Index is a numerical indicator used to measure the degree of dryness of the climate at a specific location. It is calculated by dividing the annual precipitation by the potential evapotranspiration (the amount of water that could be evaporated and transpired if there was sufficient water available). A higher aridity index indicates a drier climate. This index is useful in studying climate change, drought conditions, and water resource management.

## How to Calculate Aridity Index?

The following steps outline how to calculate the Aridity Index.

- First, determine the annual precipitation (P) in millimeters (mm).
- Next, determine the potential evapotranspiration (PET) in millimeters (mm).
- Next, gather the formula from above: AI = P / PET.
- Finally, calculate the Aridity Index.
- After inserting the values for P and PET and calculating the result, check your answer with the calculator above.

**Example Problem:**

Use the following variables as an example problem to test your knowledge.

Annual precipitation (P) = 500 mm

Potential evapotranspiration (PET) = 300 mm