ToolsGrowing degree days
This PropelMapper calculator turns your daily Fahrenheit highs and lows into a corn heat-unit total using the 86/50 method.
Use Fahrenheit, with a high and low separated by a comma, space or tab. A date may be present but is not used to order rows or remove duplicates. The starting temperatures are examples.
The three starting temperature pairs are examples. Replace them with the weather record for your chosen period.
| Measure | Result |
|---|---|
| Growing degree daysModified method, 86/50 °F | 54.5 GDD |
| Days counted | 3 days |
| Average per day | 18.2 GDD / day |
You have a temperature record for the days you want to discuss with the grower. You paste the highs and lows here, then compare the accepted day count with that record. Missing dates stay missing; the calculator does not fetch them.
At the field, you look at the plants and record their stage separately. You can say the calculated heat total into the visit note with the temperature source and period, so the report has the basis for the number.
We prepare the report after your notes upload. You read it and explain the heat accumulation alongside what you saw in the crop. The total does not supply the field observation.
“The three example days total 54.5 corn growing degree days with the 86/50 method. I am keeping the temperature source and period with the calculation. I will record the crop stage from the plants separately.”
The three example temperature pairs total 54.5 corn GDD using the 86/50 method. The source and period belong with this calculation.
Crop stage is a separate observation from the field visit.
The three example temperature pairs total 54.5 corn GDD using the 86/50 method. The source and period belong with this calculation.
Crop stage is a separate observation from the field visit.
After your review
This tool holds each high and low between 50 °F and 86 °F, averages the adjusted pair and subtracts 50 (Iowa State corn GDD method).
The total adds valid temperature pairs. Dates do not sort the rows, remove duplicates or supply missing days. The accepted day count can be compared with your weather record; unreadable rows are skipped.
The example raises the 40 °F low to 50 °F and lowers the 92 °F high to 86 °F. The daily values are 17.5, 8 and 29 GDD. Their sum is 54.5; the large result rounds it to a whole number.