GDU Calculator — Growing Degree Units
Calculate daily and accumulated Growing Degree Units (GDU) — also called Growing Degree Days (GDD) — from daily temperature readings, a crop-specific base temperature, and the number of days in the growing period.
°C
°C
°C
Heat units accumulated per day above the base temperature
- 1
Average daily temperature
(26 + 12) ÷ 2 = 19 - 2
Daily GDU = avg temp − base temperature
max(0, 19 − 10) = 9If the average temperature is at or below the base, GDU is zero — no development occurs.
Hoe werkt deze rekenmachine?
Growing Degree Units (GDU) = max(0, (Tmax + Tmin) / 2 − Tbase) per day, accumulated over a period. They measure crop-available heat above a species-specific base (often 10 °C for maize, 5 °C for cereals). Enter daily temperatures, base temperature, and number of days to get daily and cumulative GDU and an estimate of days to reach a target stage.
Formule
How this is calculated
Plants develop not by calendar time but by accumulated heat. Growing Degree Units (GDU, also called Growing Degree Days or GDD) measure how much warmth a crop has received above the threshold below which growth stalls — the base temperature. Each day, the mean temperature (average of the daily high Tmax and daily low Tmin) is compared with this threshold; if it exceeds it, the difference is that day's GDU contribution. If the mean equals or falls below the base, the contribution is zero (plants do not "reverse" due to cold).
The base temperature is crop-specific: 10 °C is the standard for maize (corn), 5 °C for many small-grain cereals and grasses, 4.4 °C for cool-season vegetables. Agronomists publish GDU thresholds for key development events — for example, maize silking typically occurs around 200 GDU after emergence and black-layer maturity around 800–1000 GDU, though the exact targets depend on variety.
This calculator assumes constant daily temperatures equal to the values you enter, which approximates well for multi-day averages but not for highly variable climates. Some regions use a method that caps Tmax at an upper threshold (e.g. 30 °C for maize) to account for reduced development at extreme heat — this calculator uses the simpler uncapped formula. Always consult your seed supplier or regional agronomist for variety-specific GDU requirements.
Veelgestelde vragen
Base temperature is crop-specific. Common values: maize = 10 °C, wheat/barley = 5 °C, cool-season vegetables = 4–5 °C, soybeans = 10 °C, sunflower = 6–8 °C. Your seed supplier or local extension service will have variety-specific values.
Growing Degree Units (GDU) and Growing Degree Days (GDD) refer to the same concept: accumulated heat above a base temperature. The term GDU is more common in North American maize agronomy; GDD is used more broadly in other crops and regions. The formula is identical.
Zero daily GDU means the average daily temperature is at or below the base temperature — there is no net heat accumulation for development. This is normal in early spring or cool climates before the growing season proper begins.
Ook bekend als
TG we-Calculate Editorial Team. (2026). GDU Calculator — Growing Degree Units [Online calculator]. TG we-Calculate. https://we-calculate.com/nl/calculator/gdu-calculator
TG we-Calculate Editorial Team. "GDU Calculator — Growing Degree Units." TG we-Calculate. 2026. https://we-calculate.com/nl/calculator/gdu-calculator.
TG we-Calculate Editorial Team, "GDU Calculator — Growing Degree Units," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/nl/calculator/gdu-calculator
@misc{wecalculate_gdu_calculator, title = {GDU Calculator — Growing Degree Units}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/nl/calculator/gdu-calculator}}, year = {2026}, note = {TG we-Calculate} }
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