Harvest Date Calculator | Free Crop Yield Tool

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Predict harvest timing from Growing Degree Days accumulation.

Results

Base Temperature-

GDD per Day-

Required GDD-

Days to Harvest-

Estimated Harvest Date-

How to Use This Calculator

Enter the required input values in the form fields above. Each field includes default values that you can adjust to match your specific situation. Click the Calculate button (or simply change any input) to see instant results. Use the Metric/Imperial toggle to switch between unit systems. Results are displayed in the results panel and can be used for farm planning and decision-making.

About This Tool

This calculator is designed to help farmers, agronomists, and agricultural students make quick, accurate calculations for farm management. It uses standard agricultural formulas based on extension service recommendations and scientific literature. Whether you are planning inputs, estimating yields, or managing finances, this tool provides reliable estimates to support your decisions.

Applicability: Applicable to major field crops (corn, soybeans, wheat) in North America and Europe, adaptable worldwide.

How the Calculation Works

Daily GDD = (Tmax + Tmin) ÷ 2 − Base temperature. Base temperatures: corn and soybean 50°F (10°C), wheat 32°F (0°C). Required GDD ≈ relative maturity × crop factor (corn ≈ 25, soybean ≈ 26, wheat ≈ 20). Days to harvest = Required GDD ÷ Daily GDD. Harvest date = planting date + days to harvest.

Real-World Example

Corn, planted April 20, 110 RM, average 70°F: base 50°F, daily GDD = 20, required GDD ≈ 2,750. Days = 2,750 ÷ 20 = 138 days. Estimated harvest ≈ September 5.

Common Mistakes & Tips

Common mistakes: using a single year's average temperature; forgetting that GDD stops above the upper cutoff (≈86°F); applying corn factors to wheat; ignoring rainfall and stress that delay maturity. Use long-term average temperatures for planning.

Reviewed by Agricalc Editorial Team — Agricultural engineers and agronomists with 10+ years of field experience. Our team verifies every calculator formula against peer-reviewed extension publications. For site-specific advice, consult your local agronomist.

References

Frequently Asked Questions

What is GDD?

Growing Degree Days (GDD) measure heat accumulation above a crop's base temperature. Each day's GDD = average temperature − base. Crops develop only when GDD accumulate; maturity is reached after a species- and variety-specific total.

What are the base temperatures?

Corn and soybeans use a 50°F (10°C) base; winter wheat uses 32°F (0°C) for spring green-up. Daily GDD below the base is zero, not negative.

How accurate is the harvest date?

It is a planning estimate. Actual maturity shifts with heat, moisture, pests and variety. Use long-term average temperatures and treat the date as ±7 days.

Should I use average daily temperature or Tmax/Tmin?

Best practice uses (Tmax + Tmin)/2. If you only have the daily average, that is an acceptable approximation. Tmax above 86°F is typically capped (86/50 rule for corn).

How does this help with planning?

It lets you schedule custom combines, drying capacity, labor and storage ahead of time, and compare how early vs late planting affects harvest timing across your fields.