GDU Calculator – Growing Degree Units
Enter the day’s high and low temperatures to calculate Growing Degree Units, a common measure of daily crop heat accumulation.
What this calculator does
The GDU Calculator (Growing Degree Units) estimates how much heat a crop — most commonly corn — accumulated in a single day, which growers use to track plant development stages and predict maturity dates.
How the formula works
This calculator uses the modified corn GDU formula: the day’s high temperature is capped at a ceiling of 86°F (since most crops don’t develop faster above this point) and both the high and low are floored at the base temperature of 50°F (since little growth happens below it). GDU is then ((adjusted high + adjusted low) ÷ 2) − base temperature.
- A day with a high of 85°F and low of 60°F and a 50°F base yields 22.5 GDU
- Corn typically needs a running total of 2,300-2,900 GDU to reach maturity, depending on the hybrid
A note on accuracy
Different crops use different base and ceiling temperatures (this calculator defaults to the standard 50°F base commonly used for corn); check your specific crop’s recommended base temperature for the most accurate results, and note this tool calculates a single day’s GDU, not a cumulative seasonal total.