Semi-Log Graph Paper
Semi-log graph paper has a logarithmic y-axis and a linear x-axis — exactly what you need to plot exponential growth or decay as a straight line. Use it for science labs, engineering, and any time your data spans several orders of magnitude. Print or download a vector PDF.
What is semi-log paper?
- One axis (usually the vertical) is divided into "decades" — each decade is 10× larger than the one below it.
- The other axis is plain linear, spaced evenly.
- When a quantity grows exponentially, its plot on semi-log paper becomes a straight line, which is much easier to fit and interpret than a curve.
What is it good for?
- Plotting exponential growth — bacterial populations, compound interest, viral spread.
- Plotting exponential decay — radioactive isotopes, drug concentrations.
- Frequency response curves in electronics and signal processing.
- pH and chemistry — a pH change of 1 unit is a 10× change in concentration.
Semi-log vs log-log
- Semi-log — one axis logarithmic, the other linear. Use it when only one variable spans several orders of magnitude.
- Log-log — both axes logarithmic. Use it for power-law relationships where both variables span large ranges.
Frequently asked questions
What is semi-log paper used for?
Plotting any data set where one variable changes exponentially. The exponential variable goes on the log axis; a straight line on the plot indicates exponential behavior.
How many decades does the paper have?
The number of decades depends on your spacing and paper size. A typical Letter or A4 page fits 3–4 decades on the log axis.
Can I switch which axis is logarithmic?
The current generator places the log scale on the y-axis. Rotate the page to landscape if you need a horizontal log axis.
Will it work for biology and chemistry labs?
Yes. Semi-log paper is the standard for growth curves, decay curves, and reaction rate plots.
Is it the same as logarithmic paper?
Semi-log is a specific kind of logarithmic paper — only one axis is logarithmic. Log-log paper has both axes logarithmic.