Growing Degree Units Calculator
Find growing degree units for a day.
GDUs track heat accumulation that drives crop development.
How the Math Works
Growing Degree Units (GDUs) are calculated using a simple yet powerful formula that quantifies plant development based on temperature. The calculation takes the daily maximum and minimum temperatures, averages them together, and then subtracts a base temperature specific to each crop. This base temperature represents the minimum threshold below which plant growth stops entirely. For example, if corn has a base temperature of 50°F, and you record a high of 85°F and low of 55°F, the GDU would be ((85 + 55)/2) - 50 = 25 GDUs. The result is always a positive value, as negative outcomes are set to zero, since plants cannot accumulate growth units when temperatures are too low.
Practical Applications
To apply this calculation, first identify the base temperature appropriate for your specific crop or plant species, which can typically be found in agricultural extension resources or seed catalogs. Record the daily maximum and minimum temperatures either from a weather station, personal weather station, or online weather service. Enter these values into the calculator, and it will instantly provide your GDU accumulation for that day. Agricultural professionals often track cumulative GDUs throughout the growing season to predict key developmental stages like emergence, flowering, or harvest timing, enabling more precise irrigation, fertilization, and pest management decisions.
Day-to-Day Use
In daily life, this calculator helps gardeners and farmers understand exactly how much progress their plants are making each day. Instead of guessing whether it's time to plant, transplant, or harvest, you can rely on scientific data showing your plants' actual growth rate. This means you can plan garden activities with confidence, knowing that after accumulating 150 GDUs your tomato plants will likely be ready for their first fruit set. It also helps explain why some years seem to accelerate through spring while others crawl—monitoring GDUs turns temperature fluctuations into actionable insights for better gardening outcomes and more abundant harvests.
Worked example
High 85, low 60, base 50 → 22.5 GDU.
FAQ
Why track?
Crop stages occur at predictable cumulative GDU totals.