Printable Protractor
Calibration checked · How we check
Marked every degree, numbered every ten, with the reverse scale inside so the same tool reads an angle opening left or right. Line the cross-hair up on the vertex and the baseline along one arm.
Before you print
- Set the print scale to 100% — not “fit to page”, which shrinks by a few percent.
- Print, then measure the reference bar below with a ruler you trust.
- If it is not exactly 100 mm, type what you measured and print again.
Printed at 100% on A4 or US Letter. Paper stretches with humidity, so re-check the reference bar if precision matters.
What it is for
- —Setting a mitre by hand when the saw scale is unreadable.
- —Checking an angle on a drawing that has no dimension on it.
- —Homework, where the plastic one has always gone missing.
Why the calibration step exists
The drawing is exact — every mark is placed in absolute units, so a millimeter in the file is a millimeter on paper. What is not exact is the path from file to sheet. Print dialogs default to fitting the page, which rescales by a few percent, and printers differ from each other regardless. Nothing in a web page can detect that; only measuring the printed sheet can. The reference bar is there so the error is visible in one look, and the scale field is there so you can cancel it out.