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Name the Angle: Acute, Right, Obtuse, Straight or Reflex

📐 Angles & ProtractorAge 8-10MediumAngles🇺🇸 3rd–4th Grade🇬🇧 Year 3–5🇦🇺 Year 3–4🇮🇳 Class 3–4📐 4.G.A.1📐 4.MD.C.5

Next: Estimate the Angle →

Most children learn acute, right and obtuse angles first, but then they meet a big one that opens past a straight line. That is a reflex angle, and it measures more than 180 degrees but less than 360 degrees.

In this free activity your child looks at an angle on screen and chooses its correct name: acute, right, obtuse, straight or reflex. Angles are shown in neat steps of 10 degrees, so the sizes are easy to judge by eye. It is a quick, calm way to build angle sense before moving on to measuring with a protractor.

How to play

  1. Look carefully at the angle shown between the two arms.
  2. Compare it with a right angle (a square corner) and with a straight line.
  3. Tap the correct name: acute, right, obtuse, straight or reflex.
  4. Keep going until all ten questions are done, then try again for a faster score.

This activity helps children build a strong mental picture of angle size before they pick up a protractor. By comparing every angle with a square corner (90 degrees) and a straight line (180 degrees), your child learns to sort angles into five clear groups, including the tricky reflex angle that many learners miss. Along the way they practise careful looking, mathematical vocabulary and quick reasoning instead of guessing. The skills here support later work on measuring and drawing angles, angles on a straight line, triangles and turns in geometry. Ten short questions make it easy to fit into homework time or a five-minute revision break.

Frequently asked questions

What is a reflex angle?
A reflex angle is any angle larger than 180 degrees but smaller than 360 degrees. It looks like the bigger opening on the outside of an ordinary angle. For example, if one angle measures 70 degrees, the reflex angle beside it measures 290 degrees.
What age is this angles activity for?
It suits children around 8 to 10 years, or Class 4 and Class 5. Younger children who already know right angles can try it with an adult, while older students can use it as fast revision before measuring angles with a protractor.
How can my child tell an obtuse angle from a reflex angle?
Ask them to picture a straight line, which is 180 degrees. An obtuse angle is bigger than a right angle but still smaller than that straight line. A reflex angle has opened past the straight line, so it looks wider than half a turn.
Do we need a protractor for this activity?
No, a protractor is not needed. This activity trains the eye to judge and name angle types. Once your child is confident, a real protractor is a great next step for measuring exact sizes and drawing angles on paper.
Is this activity free to use?
Yes, it is completely free and works in a browser on a phone, tablet or computer. There is no sign-up, so parents and teachers can open it straight away for home practice, revision or a short warm-up in class.

More angles & protractor

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Updated 5 Nov 2026