Growing Degree Units (GDU) Calculator
Enter a day's high and low temperature and the base temperature for your crop or model to get growing degree units. Choose the simple average method or a modified method with a temperature ceiling and floor, and optionally multiply across days.
Last updated: September 25, 2026
Frequently asked questions
What are growing degree units?
They measure how much heat accumulated in a day above a crop's base temperature. Adding them up across the season tracks crop development better than calendar days.
Are growing degree units the same as growing degree days?
In most uses they refer to the same heat-accumulation idea, but exact conventions (base temperature, caps, units) vary between sources. This tool shows the method used so you can match your reference.
What base temperature should I use?
It depends on the crop and model. Use the base your seed company, extension service, or model specifies. The default of 50°F is only a common starting point.
What does the modified method do?
It limits the maximum temperature at 86°F (30°C) and raises the minimum to the base temperature, because plant development slows in extreme heat and stops below base.
Why is my result zero?
The average temperature was at or below the base temperature, so no heat units accumulated. Daily GDU is never negative here.
Can it add up a whole season?
This tool multiplies one day's value by a number of days. For a real season, add up each day's own result from actual weather data.