Gdu Calculator
Calculate Growing Degree Units (GDUs) accumulated per day — a measure of heat accumulation used to predict crop and plant development.
Formula
GDU/day = MAX([(Tmax + Tmin)/2 − 50°F], 0)
- Base temperature for most crops (corn, soybeans) is 50°F.
- Tmax is capped at 86°F; Tmin below 50°F is treated as 50°F.
- Corn needs ~2,700 GDUs to reach black layer; silking at ~1,250 GDUs.
Tmax=80°F, Tmin=55°F over 30 days
Inputs
- Maximum Daily Temperature: 80 °F
- Minimum Daily Temperature: 55 °F
- Number of Days: 30
GDU/day = (80+55)/2 - 50 = 67.5 - 50 = 17.5. Total = 17.5 × 30 = 525 GDUs.
Frequently asked questions
What are GDUs used for?
Predicting crop milestones like silking, pollination, and maturity in corn and other crops.
What is the base temperature?
50°F for corn and many warm-season crops; 40°F for small grains.