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Free Online Protractor

About

About Us

Free Online Protractor is a browser-based tool for measuring angles on photos, diagrams, and PDFs — with no account, no ads, and no upload.

Our mission

Measuring an angle on a photo or a PDF drawing is a small, common task: checking a roof line, marking up a diagram for homework, verifying a corner on a drawing, reviewing a design. We built this tool so anyone can do that without installing software, creating an account, or paying for features that should be basic.

Everything is available at no cost. Nothing is claimed that cannot be demonstrated.

What we offer

  • Measure angles on PNG, JPG, WebP, GIF, SVG, and PDF files
  • Multiple measurements, chain angles, ruler calibration, and grid overlays
  • Export to CSV, SVG, PNG, and print-ready PDF reports
  • Honest per-measurement ± uncertainty on every reading
  • Full privacy: files stay on your device and are never uploaded

See the full capability list on Features or try the tool on the homepage.

How it is built

A static site with one interactive component. The measurement geometry is a small, pure, unit-tested module; the drawing surface is SVG, which is what makes the handles keyboard-operable and announceable by a screen reader — something a canvas-based tool cannot offer. PDF rendering is loaded only when you open a PDF, so the page stays light for everyone else.

There is no server-side component. Not as a privacy policy, but as architecture: there is nowhere for your images to go.

What we believe

  • Free means free. No paywalls, no “pro” tier, no ads.
  • Privacy by design. Local-only processing, verifiable in your browser's Network tab.
  • Honest accuracy. Per-measurement uncertainty instead of a misleading headline figure.
  • Accessible tools. Keyboard navigation, screen reader support, and touch-friendly controls.

What we do not claim

There are no user counts, star ratings, or testimonials on this site. A new tool has not earned them, and inventing them is the most common form of dishonesty in this category. If numbers appear here later, they will be ones that can be substantiated.

There is also no headline accuracy figure, for the reasons set out on theaccuracy page. What you get instead is a per-measurement uncertainty derived from your own measurement.

Contact us

Questions, bug reports, and corrections to the mathematics are welcome. Corrections to the accuracy documentation matter more than cosmetic bugs.Contact Us or emailhello@freeprotractoronline.com.

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