WebPlotDigitizer — The Complete Guide: Extracting Data From Plots in Standards and Catalogues
WebPlotDigitizer solves a familiar problem: a curve that exists only as a picture — in an old standard, a manufacturer’s catalogue or a paper — and you need numbers from it. You load a scan or photo, calibrate the axes from two known points and get a table of values.
WebPlotDigitizer
Ankit Rohatgi / Automeris
Extracts numeric data from images of plots and charts — curves from old standards, datasheets and papers.
Get it from the vendorWhat you get
- Axis calibration — from two known points on each axis.
- Manual or automatic tracing — pick points by hand or let it detect the curve.
- Plot types — Cartesian, logarithmic, polar and ternary.
- Maps and distances — measure distances on a calibrated image.
- Table of values — ready for a spreadsheet or a script.
Editions and licence
The code is open source (AGPL-3.0) and use is free, including commercial work. The previous, archived edition is available as a free offline desktop app for Windows, macOS and Linux. The new online version requires sign-up and limits how many images you can process for free.
Related tools
To plot and analyse the extracted data — LabPlot or SciDAVis. To fit a curve in code — Python.
LabPlot
KDE
Data analysis and scientific plotting in a graphical interface — a free alternative to Origin, with curve fitting and FFT.
Get it from the vendorSciDAVis
SciDAVis (open-source project)
Scientific data analysis and publication-quality plotting — tables, curve fitting and Python scripting.
Get it from the vendor
gnuplot
gnuplot Project
Publication-quality plotting driven from scripts.
Get it from the vendor
Python
Python Software Foundation
The language behind most modern engineering computation, and its full ecosystem.
Get it from the vendorThe bottom line
A small tool that saves hours of reading values off a printed chart with a ruler. Check a few points against the original before you use the result in a calculation.