Trade Toolkit

Tools › Finish Carpentry

Angle finder: read a corner with your phone

Your phone reads the corner and the miter.

Open the Angle Finder tool

Free. Runs in your browser, no account, and keeps working offline.

What it does

Hold your phone flat against one wall, tap, then hold it against the other wall and tap again. The phone's motion sensors measure how far it turned, and the tool shows the corner angle and the miter for each piece of flat trim.

Few corners are exactly 90°. A wall that is two degrees out leaves a gap at a 45° miter; reading the real corner first lets you cut it right the first time. Take the corner to the Miter & Crown calculator for crown settings.

Laid on a surface, it also reads the slope from level. A phone sensor is a field aid, not a precision instrument: check critical cuts with a test piece.

Worked example

Hold the phone flat against one wall, then the other. The phone turned 88° between them.

Corner angle
92.0°
Miter for flat trim (each piece)
44.0°

A corner that is not quite square is why a 45° cut leaves a gap; this reads the real one.

Try it with your numbers

Questions

How do I find the angle of a corner without a protractor?

Hold the phone flat on the first wall, then on the second. The turn between them gives the corner: a 88° turn is a 92° corner, cut at 44° per piece.

Does it need an internet connection?

No. It uses the phone's own sensors and works offline once the toolkit has loaded.

How accurate is it?

Phone sensors are usually good to about a degree. For a tight joint, cut a test pair on scrap and adjust.

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