Barley GDD (Heat Units) Calculator
Calculate growing degree days for barley (base 5°C, ~1700 GDD to maturity) and estimate days to maturity from temperature.
Barley has a base temperature of 5°C and needs about 1700 growing degree days to mature. Accumulate daily GDD from sowing to predict each growth stage and the harvest date better than the calendar can.
Indicative planning figures based on published research averages. Local soil tests, varieties and weather change actual requirements — confirm with your agronomist or extension officer.
Agronomists use the free Barley GDD Calculator to track crop development by heat units instead of calendar days, predicting growth stages and harvest timing more accurately.
About Barley GDD (Heat Units) Calculator
Crops develop in response to accumulated heat, not calendar days. Barley has a base temperature of 5°C — below which it barely grows — and needs roughly 1700 growing degree days (GDD) to reach maturity. Each day adds GDD = (Tmax + Tmin)/2 − 5°C (capped at an upper threshold). This tool computes today's GDD and, from your accumulated total, estimates how many days remain to maturity at the current temperatures — far more reliable than counting days on a calendar across variable seasons.
How to use Barley GDD (Heat Units) Calculator
- 1Enter today's max and min temperature.
- 2Optionally enter the GDD accumulated since sowing.
- 3Read today's GDD, the estimated days to maturity and the progress percentage.
Why use Barley GDD (Heat Units) Calculator?
- ✓Uses barley's real base temperature and GDD-to-maturity
- ✓Estimates days to maturity from temperature, not the calendar
- ✓Tracks % progress to maturity
- ✓Free, instant and fully in-browser
Frequently asked questions
What is the base temperature for barley?+
About 5°C. Below this temperature barley makes little or no growth, so GDD is calculated as the daily mean temperature minus 5°C.
How many growing degree days does barley need?+
Roughly 1700 GDD from sowing to maturity, depending on variety. Accumulating daily GDD and comparing to this total predicts maturity and harvest better than a fixed number of days.
Why use GDD instead of days after sowing?+
A warm season pushes a crop to maturity in fewer days than a cool one. Heat units (GDD) capture that, so the same GDD total reliably marks the same growth stage across different seasons and sowing dates.
Is this tool free and private?+
Yes — free, no sign-up, and all calculation runs in your browser, so it works offline in the field and your data never leaves the device.
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