Logarithmic graph paper
Logarithmic rulings for data spanning several orders of magnitude, set here to four decades.
Opens with these settings already loaded. Change anything you like, then download as PDF, PNG or SVG.
What the log axis is telling you
On a logarithmic axis, equal distances represent equal ratios rather than equal amounts — the gap from 1 to 10 is the same as from 10 to 100. That means constant-percentage growth plots as a straight line, and the slope of that line is the growth rate. Reading a rate straight off a ruler is why log paper survived the arrival of computers.
Diagnosing your data
Plot the same data three ways and the shape tells you the underlying relationship. Straight on linear axes means linear. Straight on semi-log means exponential — compound growth, radioactive decay, bacterial culture. Straight on log-log means a power law — allometric scaling, Zipf distributions, fluid drag. That diagnostic is often the real result.
Choosing decades
Count the orders of magnitude in your data and match. Four decades covers 1 to 10,000, which handles most laboratory work. Using more than you need flattens your curve into the middle of the sheet and throws away resolution; using fewer means running off the top of the page.
Printing it accurately
This only measures correctly if your printer doesn't rescale the page. In the print dialog set Scale: 100% — not "Fit to page" or "Shrink oversized pages". If you're not sure it worked, print the calibration page, measure the ruler on it with a real ruler, and it will tell you exactly what your printer is doing to the page.