Growing Degree Days (GDD) Calculator

Enter a day's high and low temperature in Fahrenheit to calculate growing degree days for that day. Set the base temperature to match your crop.

How it works

Growing degree days measure the heat a crop accumulates. Each day's GDD is the average of the high and low temperature minus a crop-specific base temperature, and the result is never below zero:

GDD = ( (Tmax + Tmin) ÷ 2 ) − Base  (not less than 0)

Many models cap the high at an upper threshold (86°F is common for corn) because growth does not speed up above it, and some also raise any low below the base up to the base. Enter an upper cap to use the modified method. To track a season, add up each day's GDD from planting.

Using GDD

Base temperatures reflect how much warmth a crop needs to grow: about 50°F for warm-season crops such as corn and beans, and roughly 40°F for cool-season small grains and many vegetables. Accumulated GDD predicts stages like emergence, flowering, and maturity more reliably than calendar days, which is why seed guides and pest-forecasting models are often written in degree days. Base and threshold values vary by crop and model, so match them to the guidance you are following.

This tool is a planning aid and does the math from the numbers you enter. It is not a substitute for a soil test, seed-tag information, or advice from your local Cooperative Extension office. Page updated Aug 4, 2026.