Spirit Level Tool: Protractor

A spirit level you can actually read — and a camera protractor for everything a bubble can't reach.

Rest your phone flat for a two-axis bubble, or stand it against a wall for a single vial. It switches between them on its own.

LEVEL ANY SURFACE
• Surface mode: two-axis bullseye for tables, shelves and floors
• Edge mode: classic vial for walls, posts and door frames
• Big, readable numbers you can see at arm's length
• A short buzz when you hit level, so you don't have to stare

MEASURE ANY ANGLE
• Camera protractor — line up a corner, freeze the frame, drag the two arms onto the edges
• Shows the angle and its supplement, so a 45° mitre reads 45°, not 135°
• Angle finder — zero against a reference surface, then read the difference anywhere else

SLOPE, NOT JUST DEGREES
• Percent slope for drainage and ramps
• Millimetres per metre for trade work
• Inches per foot
• Roof pitch as x:12

KEEP YOUR MEASUREMENTS
• Hold a reading so you can move the phone and still read it
• Save measurements with notes
• Export as CSV, or share the protractor shot with the angle drawn on it

BUILT FOR REAL CONDITIONS
• Daylight theme for reading in direct sun
• High contrast for low vision
• Night theme in red, so you keep your dark adaptation in a loft or crawl space

ABOUT ACCURACY
Phone sensors carry a small bias — typically within about ±0.2°. Spirit Level includes two-point calibration: take a reading, turn the phone 180° on the same spot, take another. Averaging the two cancels the surface out and leaves only your phone's own error, which is then subtracted from every reading afterwards. It takes about twenty seconds and it is the difference between a level you can trust and one you can't.

The bubble level is free, forever. Spirit Level Pro adds the camera protractor, the angle finder, every slope unit, saved measurements with export, and the outdoor themes.

Spirit Level Pro is available monthly, yearly, or as a one-time lifetime purchase. Subscriptions renew automatically unless cancelled at least 24 hours before the end of the current period. Manage or cancel any time in your App Store account settings.

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