Compare calculators

Both calculators run independently — change the inputs on either side to compare results.

Evapotranspiration Calculator

Estimate monthly potential evapotranspiration (PET) from average temperature, daylight hours, and days in the month using a simplified Thornthwaite-style formula. Returns millimetres of water lost per month.

Average Temperature (°C)

Daylight Hours (hours)

Days in Month (days)

Fill in the required fields to see your result.

Climate

Growing Degree Days Calculator

Compute daily Growing Degree Days (GDD) by subtracting a crop-specific base temperature from the average of the day's max and min temperatures. Use accumulated GDD to predict crop development stages.

Maximum Temperature (°F)

Minimum Temperature (°F)

Base Temperature (°F)

Fill in the required fields to see your result.

Key differences

	Evapotranspiration Calculator	Growing Degree Days Calculator
Category	Climate	Climate
Inputs required	3	3
Result	Potential Evapotranspiration (mm/month)	Growing Degree Days (GDD)
What it does	Estimate monthly potential evapotranspiration (PET) from average temperature, daylight hours, and days in the month using a simplified Thornthwaite-style formula. Returns millimetres of water lost per month.	Compute daily Growing Degree Days (GDD) by subtracting a crop-specific base temperature from the average of the day's max and min temperatures. Use accumulated GDD to predict crop development stages.