Polar graph paper, A3
Concentric rings and 15 degree spokes on A3, which is the size a polar plot needs when it has to be read precisely.
Opens with these settings already loaded. Change anything you like, then download as PDF, PNG or SVG.
Polar plots reward size
A polar plot crowds toward the center by construction: near the origin the spokes converge and there is almost no room between them, so a small sheet loses all resolution exactly where you may need it. Doubling the sheet to A3 doubles the radius and quadruples the plotting area, which pushes the useful region outward and makes the inner rings usable rather than decorative.
Where large polar plots actually get used
Antenna radiation patterns, loudspeaker and microphone polar response, light distribution curves in lighting design, and wind roses in meteorology. All of them share a shape: a magnitude that varies with direction, measured at intervals around a full circle. All of them also tend to be presented rather than filed, which is a second argument for the larger sheet.
Match the spoke count to your measurement interval
Fifteen degrees gives 24 divisions, which suits measurements taken every fifteen degrees around a circle. If you measured every ten, set the spokes to ten so your data points land on lines rather than between them. Reading a value that falls between spokes is guesswork, and on a plot with 24 of them the guess is worse than it looks. The 30 degree sheet is the coarser option.
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.