Growing Degree Days Calculator — Two Published Methods
Point it at a daily maximum and minimum, or at a sub-daily temperature column it can take the daily extremes from, and get the accumulation over the season. Two methods, both traceable: the simple average as the EPA defines it, and single sine after Baskerville and Emin, whose closed forms are checked in the test suite against numerical integration and against a published worked example.
Your data
Drop your logger CSV or Excel file here
CSV, TSV and .xlsx workbooks. HOBOware and Postlad exports are recognised on sight, and most other files are read anyway. It stays on this machine — the workbook is even unzipped here, and nothing is uploaded.
Synthetic daily maximum and minimum temperatures for a 122-day spring-to-summer season, 1 March to 30 June, as plain CSV in °C. Cold early days fall below the default 10 °C base and contribute nothing; late June reaches the low thirties, so the upper-threshold option and the two methods have something to disagree about. Not measured data.
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Options
Series
Leave empty to take the daily extremes from a single temperature column.
Used only when no maximum and minimum pair is chosen.
Method
The two agree on days that stay between the thresholds and diverge on days that cross one.
In the same units as the file. 10 for °C, 50 for °F. Nothing is converted.
More options — method, figure
Method
Figure
All of that was worked out in this browser tab. Your file was not uploaded, and no request goes out while you work — open the network panel and watch, if you like.
How this tool’s arithmetic is checked — the published worked examples this tool reproduces, printed beside what it computes, with the test files that assert them.