Estimate first
Before measuring, decide if the angle is acute or obtuse. If it is clearly less than a right angle, the answer cannot be 130° — you read the wrong scale.
Angles Lab 📐
Measure and draw angles with an on-screen protractor, see the angle rules move as you drag, and practise finding missing angles — always with the reason.
On-screen protractor
Angle rules
Reasons given
Nothing leaves your device
The angle
How to measure
- Put the centre of the protractor on the corner (the vertex).
- Line up 0 with one arm of the angle.
- Read the scale that starts from 0 on that arm — not the other one.
What is true
x =°
Good to know
Always give the reason
In an exam, "x = 62°" earns less than "x = 62° because angles on a straight line add up to 180°". The rules page writes the reason beside every answer.
Nothing leaves your device
Everything runs in your browser and nothing is saved, not even practice scores.
Tool created by
លោក ណាត ប៊ុនឆ័យ · Mr. Nat Bunchhai
Alpha Academy Cambodia
Geometry is easier with a tutor beside you.
Our tutors guide students through angles, shapes and proofs, from Stage 7 to Grade 12.