Tomato GDD (Heat Units) Calculator
Calculate growing degree days for tomato (base 10°C, ~1400 GDD) and estimate days to maturity.
Tomato accumulates ~1400 GDD from transplant to first ripe fruit; heat units predict picking better than days. GDD = (Tmax + Tmin)/2 − 10°C; accumulate from sowing to predict stages and harvest.
Indicative planning figures based on published research averages. Local soil tests, varieties and weather change actual requirements — confirm with your agronomist or extension officer.
Growers use the free Tomato GDD Calculator to schedule the crop by accumulated heat units rather than calendar days, improving harvest and stage prediction.
About Tomato GDD (Heat Units) Calculator
Tomato develops by accumulated heat, not calendar days. With a base temperature of 10°C and roughly 1400 growing degree days to maturity, daily GDD = (Tmax + Tmin)/2 − 10°C. Tomato accumulates ~1400 GDD from transplant to first ripe fruit; heat units predict picking better than days. Enter today's temperatures and your accumulated GDD to see today's heat units, the estimated days to maturity at current temperatures, and the progress to harvest.
How to use Tomato GDD (Heat Units) Calculator
- 1Enter today's max and min temperature.
- 2Optionally enter accumulated GDD since sowing.
- 3Read today's GDD, days to maturity and progress.
Why use Tomato GDD (Heat Units) Calculator?
- ✓Uses tomato's base temperature and GDD-to-maturity
- ✓Predicts maturity from heat units, not the calendar
- ✓Tracks progress to harvest
- ✓Free, instant and fully in-browser
Frequently asked questions
What base temperature does tomato use for GDD?+
About 10°C. Daily growing degree days are the mean temperature minus 10°C, so little development is credited on days below that threshold.
How many GDD does tomato need?+
Roughly 1400 growing degree days to maturity. Tomato accumulates ~1400 GDD from transplant to first ripe fruit; heat units predict picking better than days.
Why track heat units instead of days?+
Because temperature drives development: the same GDD total marks the same growth stage whether the season is warm or cool, making GDD a better scheduling tool than days after sowing.
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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