Harvest Date Calculator
Estimate expected harvest date from planting date using growing degree day (GDD) requirements by crop.
Results
Visualization
How It Works
Crops mature based on accumulated heat units called Growing Degree Days (GDD), not calendar days. GDD = average daily temperature minus a base temperature. Corn uses base 50°F; wheat uses base 32°F. A 110-day corn hybrid needs about 2,695 GDD.
The Formula
Daily GDD = Max(0, Avg Daily Temp − Base Temp)
Days to Maturity = Total GDD Required ÷ Daily GDD
Harvest Date = Maturity + Dry-Down Days
Days to Maturity = Total GDD Required ÷ Daily GDD
Harvest Date = Maturity + Dry-Down Days
Variables
- GDD — Growing Degree Days — heat units above the crop base temperature
- Base Temp — Minimum temperature for crop growth (corn/beans: 50°F, wheat: 32°F)
- Dry-Down — Days after maturity to reach harvest moisture (corn: ~14 days)
Example
110-day corn planted April 25 with 72°F average: needs 2,695 GDD at 22 GDD/day = 123 days to maturity + 14 dry-down = harvest around Aug 26.
Tips
- Switch to shorter-maturity hybrids if planting late (after May 15 in the Corn Belt).
- Early frost risk increases with later maturity — check frost date tables.
- GDD calculators from your state extension service use actual daily temperatures.
- Corn grain dries about 0.5-0.75% moisture per day in the field after maturity.