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Corn Heat Units Calculator (GDD)
Calculate modified corn growing degree days (base 50°F, 86°F cap) and track season progress.
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Result
How it's calculated
Modified GDD = (capped high + floored low) ÷ 2 − 50. The daily high is capped at 86°F and the low is floored at 50°F before averaging, because corn's growth rate roughly plateaus above 86°F and stalls below 50°F.
| Stage (from planting) | Approx. GDD |
|---|---|
| Emergence (VE) | 90–120 |
| V6 | ~475 |
| Tassel / silk (VT/R1) | ~1,250–1,400 |
| Physiological maturity (R6 / black layer) | ~2,300–3,000 |
Maturity GDD varies widely by hybrid relative-maturity rating — check the seed tag for a hybrid-specific number.
Row Wise accumulates modified corn GDD automatically from your field's real weather and flags growth stages and nitrogen sidedress timing — no manual log.
Get notified at launch →Frequently asked questions
What are corn GDD or growing degree days?
GDD (growing degree days, modified method, base 50°F) measure the heat corn accumulates each day toward development. Corn development tracks accumulated heat far more reliably than calendar days.
Why cap the high at 86°F and floor the low at 50°F?
Corn's growth rate doesn't keep increasing above about 86°F, and doesn't grow below 50°F, so the "modified" GDD method flattens the high and floors the low to reflect that plateau.
How many GDD does corn need to reach maturity?
It depends heavily on hybrid relative maturity — full-season hybrids often need 2,600–3,000+ modified GDD from planting to black layer, while shorter-season hybrids need less. Check your hybrid's GDD-to-maturity rating on the seed tag.