GDU Calculator (Growing Degree Units)

Growing Degree Units (GDUs) measure accumulated heat over a growing season to predict when crops like corn or wheat will reach key development stages. Enter your Maximum Temperature, Minimum Temperature, Base Temperature (by crop type), and Number of Days into the GDU Calculator to get Total Growing Degree Units and Average Daily GDU. Optionally enter a Comparative Relative Maturity (CRM) rating for your corn hybrid to also see Progress to Silking and Progress to Maturity.

°F

Daily maximum temperature

°F

Daily minimum temperature

Temperature below which plant growth stops

Period for GDU accumulation calculation

CRM

Corn hybrid maturity rating

Results

Total Growing Degree Units

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Average Daily GDU

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Progress to Silking

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Progress to Maturity

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Frequently Asked Questions

What is GDU? Growing degree units definition

Growing Degree Units (GDU), also known as Growing Degree Days (GDD), are a measure of heat accumulation used to predict crop growth stages. GDUs quantify the amount of heat available over a growing season, helping optimize planting schedules and harvest planning.

How do I calculate GDU for corn?

GDU is calculated using the formula: GDU = (Maximum Temperature + Minimum Temperature) ÷ 2 - Base Temperature. For corn, the base temperature is typically 50°F. Any negative values are set to zero.

How many GDUs does corn need to emerge?

Corn typically needs 90-120 GDUs to emerge from planting, depending on soil conditions and planting depth. Full emergence usually occurs within 100-150 GDUs under normal conditions.

What is the base temperature?

Base temperature is the minimum temperature below which plant growth stops. For corn, it's 50°F. Cool season crops like wheat use 40°F, while warm season crops may use 60°F as their base temperature.

How do GDUs affect planting schedules?

GDUs help determine optimal planting times by tracking accumulated heat units. Farmers can use historical GDU data to predict when soil conditions will be suitable and when crops will reach critical growth stages.

Are data available for my location?

GDU calculations require local temperature data. You can obtain this from weather stations, agricultural extension services, or online weather databases. Many agricultural websites provide location-specific GDU tracking tools.

What does CRM mean in corn production?

Comparative Relative Maturity (CRM) is a rating system that indicates how many GDUs a corn hybrid needs to reach physiological maturity. Higher CRM numbers indicate longer-season hybrids that require more heat units.