Growing Degree Day Calculator
Crops grow on accumulated heat, not calendar days. Growing degree days measure that heat so you can predict development stages, time applications, and plan for maturity before frost.
Formula: daily GDD = ((high + low) ÷ 2) − base temperature, floored at zero. Corn uses a 50°F base; some models cap the high at 86°F and the low at 50°F (the heat-unit method). Season accumulation: sum daily GDD from planting; corn reaches maturity around 2,200-2,800 GDD depending on hybrid maturity rating. Use: predict emergence, tasseling, and maturity windows; time fungicide or nitrogen applications; and check whether a short-season hybrid fits your frost-free window.
FAQ
What is a growing degree day?
One GDD is the heat above a crop's base temperature in a day, roughly the average of high and low minus the base (50°F for corn). Accumulated GDD predicts crop development.
How many GDD does corn need?
About 2,200-2,800 accumulated GDD from planting to maturity, depending on the hybrid's maturity rating. Extension services publish GDD for your area to track progress.
Why cap the high temperature?
Above ~86°F, corn growth slows or stops, so uncapped models overestimate heat on very hot days. Capping high and low keeps the heat-unit estimate closer to real development.
Figures are editable example defaults for planning, not guarantees. Crop inputs, prices, and moisture handling vary by farm, region, and year — verify with your local extension service and agronomist.