Printable Logarithmic Graph Paper
Logarithmic graph paper with correctly positioned decade divisions — set either axis to a number of log cycles and leave the other linear for semi-log, or make both logarithmic for log-log.
- Free, no signup
- Exact-scale vector PDF
- Letter, A4, Legal & more
- Commercial use OK
0 makes the x-axis linear.
0 makes the y-axis linear.
36pt is half an inch — safe on virtually every printer.
Free, no signup. Print at 100% scale (not “fit to page”) so the measurements come out exact.
Live preview — US Letter (8.5 × 11"), portrait · updates as you change any setting.
Why the divisions get closer together
Within each decade the lines mark 1 through 9, positioned at log₁₀ of their value — so 2 sits about 30% of the way across the cycle, not 20%, and 5 sits at about 70%. That uneven spacing is the entire point: it's what turns exponential relationships into straight lines. Paper with evenly spaced subdivisions isn't log paper at all, and plotting on it produces wrong answers.
Semi-log vs log-log
Semi-log (one axis logarithmic) straightens exponential relationships — population growth, radioactive decay, RC discharge, compound interest. The slope of the resulting line gives the growth or decay constant. Log-log (both axes logarithmic) straightens power laws, y = axⁿ, and the slope reads directly as the exponent n. Identifying which one linearises your data tells you what kind of relationship you have.
Choosing the number of cycles
One cycle covers a factor of ten, so match the cycle count to your data's range: three cycles span 1 to 1,000, four span 1 to 10,000. Using more cycles than you need compresses the data into a corner and wastes resolution. Label the first major line with your starting power of ten and each subsequent decade follows.
Frequently Asked Questions
What is semi-log graph paper?
Paper with one logarithmic axis and one linear axis. It turns exponential relationships into straight lines, which makes growth and decay rates easy to read off directly.
What is log-log paper used for?
Power-law relationships of the form y = axⁿ. On log-log axes these plot as straight lines whose slope is exactly the exponent n, which is why it's standard in physics, biology and engineering scaling analysis.
How many cycles do I need?
One cycle per factor of ten in your data range. Data spanning 1 to 1,000 needs three cycles; 1 to 10,000 needs four. Using more than necessary squeezes your plot into part of the sheet.
Why aren't the lines evenly spaced?
Because each line sits at the logarithm of its value — 2 falls at about 30% across a decade and 5 at about 70%. That uneven spacing is what makes the paper work; evenly spaced lines would give incorrect plots.
Printing Tips
- Print at 100% scale.Turn off “fit to page” and “shrink oversized pages” — otherwise your printer rescales the sheet and the measurements no longer match.
- Match the paper size. Choose the same size here as the paper in your tray. Printing a Letter PDF on A4 (or the reverse) scales it.
- Lighter lines print better. A light grey or blue guides your work without competing with it — and it uses far less ink.
- Use heavier paper for wet media. 100gsm and up for fountain pens and markers; standard copier paper is fine for pencil.