Smart Protractor
An app that measures angles and slopes with your phone.
What Smart Protractor does
Smart Protractor is an angle finder for Android from Smart Tools co., the studio behind a whole set of phone measuring tools. It measures angles three ways: by touching the screen, with a swinging plumb line, or through the camera. It has more than 5 million installs on Google Play.
This is the app to reach for when you need an angle, not a length. In touch mode you line up two arms on the screen, like a classic protractor. Plumb mode uses a weighted line that hangs straight down, so you can tilt the phone against a roof pitch or a ramp and read the slope.
Camera mode overlays the protractor on the live view, so you can measure the angle of something you can't touch, like a staircase or a tree. You can read the tilt in degrees and zero it out if your phone reads a little off. Treat readings as a guide and check anything structural with a real tool.
The free version shows ads. The Pro version removes them and adds more units, screen capture, and a ruler, level and thread pitch gauge, but the Play listing doesn't show what it costs. The developer makes a family of similar tools, so if you like this one, you'll find matching apps for sound, distance and more.
Alternatives to Smart Protractor
Who it's for
Skip it if: iPhone owners.
Pricing
Free planFree with ads. A Pro version removes ads and adds more tilt units, screen capture, and ruler, level and thread pitch tools. The Google Play listing doesn't show its price.
Prices can vary by country. Checked 19 Oct 2026.
What people like
- Three ways to measure an angle
- Highly rated with millions of installs
- Part of a family of matching measuring tools
Watch out for
- Shows ads
- Level and ruler tools need Pro
- Pro price isn't shown on the listing
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Questions people ask
Is Smart Protractor free?
Yes, with ads. A Pro version removes ads and adds more tools.
Can Smart Protractor measure a slope?
Yes. Plumb mode shows the slope as you tilt the phone. Pro adds more units.
Is Smart Protractor on iPhone?
We only found it on Google Play.