Log Graph Paper
Built by Johnny Alto · free, no sign-up · updated July 26, 2026
Print semi-log graph paper for plotting data that spans powers of ten, like pH curves, frequency response, and exponential growth. Choose how many log decades on the vertical axis and how fine the linear horizontal grid is, and it prints to true scale.
Prints to scale at 100%. This is semi-log paper: the vertical axis is logarithmic (each decade is a factor of ten with 1-9 gridlines), the horizontal axis is a plain linear grid. One decade per inch is standard.
What semi-log paper is for
On semi-log paper one axis is logarithmic and the other is linear. The logarithmic axis compresses each power of ten, a decade, into the same physical height, with the gridlines inside a decade spaced by the logarithm of one through nine. That is why the lines start far apart near the bottom of a decade and bunch up toward the top. Plotting data that grows or shrinks by factors of ten, exponential growth, radioactive decay, pH, sound level, turns a steep curve into a straight line you can read and fit by eye.
It is standard in science and engineering: frequency response and Bode plots, chemical kinetics, population growth, and any measurement that spans several orders of magnitude on one axis while the other stays linear, such as time.
Choosing decades and printing
Pick how many decades you need on the log axis to cover your data range, and how fine the linear grid is on the other axis. Print at 100 percent with fit-to-page off so the decades keep their true height and your plotted slopes stay accurate. Download the SVG to plot on a tablet.
Frequently asked questions
What is the difference between log and semi-log paper?
Semi-log paper has one logarithmic axis and one linear axis, which is what this generator makes. Log-log paper has both axes logarithmic. Semi-log is the most common, used when one variable spans powers of ten and the other does not.
Why are the horizontal lines unevenly spaced?
The vertical axis is logarithmic, so within each decade the lines sit at the logarithm of 1 through 10. They start wide apart and bunch toward the top of each decade, which is what linearizes exponential data.
How many decades do I need?
Enough to cover the range of your data in powers of ten. If your values run from about 1 to 1000, that is three decades. You can pick two to five here.
How do I print it accurately?
Print at 100 percent with fit-to-page turned off so each decade keeps its true height and measured slopes stay correct.
More calculators
This calculator gives estimates for planning only; always confirm against your own measurements and species research. Some links are to our buying guides, which contain affiliate links. As an Amazon Associate I earn from qualifying purchases.
← All calculators · Buying guides · About · Affiliate Disclosure · Privacy Policy