Dew Point Calculator — A Dew Point Series From Your Own Data
A dew point from one pair of readings is a spreadsheet formula. A dew point from a whole record tells you something a single pair cannot: how close the air came to saturating, and when it got there. Drop in a logger export and get the dew point over time, the depression between it and the air, and every condensing spell marked — computed by inverting FAO-56 Equation 11 exactly, with the equation on the figure.
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 four-day open-field record at half-hourly intervals, as plain CSV with ISO timestamps declaring +02:00. It was generated from a drifting dew point with a diurnal temperature cycle over it, so three of the four nights cool all the way to saturation and one — the night the front passes — does not. Not measured data.
Saved projects
0 of 1Projects are stored in this browser only — never uploaded, and gone if you clear site data. Download one as a file to keep it, move it to another machine, or send it to a colleague.
Click any title, axis label, legend or note on the figure to reword it — Enter keeps it, Escape cancels, and an empty box hides the line. The numbers are not editable.
SVG is vector — scale it to any size in Illustrator, Inkscape or LaTeX without losing quality, and edit the type. Use it unless a journal insists on raster.
Options
Series
In °C. This tool never converts units.
In percent, 0–100.
More options — figure, condensation
Figure
Condensation
A tolerance for sensor error near saturation, not a physical constant. Set it to 0 for the strict definition.
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.