# pet

Numerous methods exist to calculate potential evapotranspiration. Three of the most widely-used ones are included in SWAT+, the Priestley-Taylor, Penman/Monteith, and Hargreaves equations. The codes for the three methods are listed in the table below. If a method other than Priestley-Taylor, Penman/Monteith, or Hargreaves is recommended for the area, in which the watershed is located, the user can calculate daily PET values with the recommended method and import them into SWAT+ (using [pet](/io-docs/introduction-1/climate/weather-sta.cli/pet.md) in [**weather-sta.cli**](/io-docs/introduction-1/climate/weather-sta.cli.md)). 

| Code | Option                  |
| ---- | ----------------------- |
| 0    | Priestley-Taylor method |
| 1    | Penman/Monteith method  |
| 2    | Hargreaves method       |


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