Does 6 8 10 make a right triangle?
Yes. 6² + 8² = 36 + 64 = 100, which is exactly 10², so 6-8-10 satisfies the Pythagorean theorem and forms a right triangle. It is the 3-4-5 triple doubled.
By Mateo Díaz · Last updated: July 19, 2026
Pythagorean theorem calculator
Tap a side to solve for it - the dashed side is the one being calculated.
- Hypotenuse c
- 5
- Perimeter
- 12
- Area
- 6
- Angle opposite leg a
- 36.87°
- Angle opposite leg b
- 53.13°
c = √(3² + 4²) = √25 = 5
The full answer
The check
The converse of the Pythagorean theorem says that if the squares of the two shorter sides add up to the square of the longest side, the triangle has a right angle:
The angle between the sides of length 6 and 8 is exactly 90°. The other two angles are 36.87° and 53.13° - the same as every 3-4-5 triangle, because 6-8-10 is just 3-4-5 at double scale.
Every multiple of 3-4-5 works
Scaling a right triangle changes its size but not its angles, so every whole-number multiple of 3-4-5 is also a right triangle:
| Multiple | Triple | Check |
|---|---|---|
| × 2 | 6-8-10 | 36 + 64 = 100 |
| × 3 | 9-12-15 | 81 + 144 = 225 |
| × 4 | 12-16-20 | 144 + 256 = 400 |
| × 5 | 15-20-25 | 225 + 400 = 625 |
| × 10 | 30-40-50 | 900 + 1600 = 2500 |
What if the numbers were different?
Compare the sum of the two smaller squares against the largest square:
| Sides | Compare | Verdict |
|---|---|---|
| 6, 8, 10 | 100 = 100 | Right triangle |
| 6, 8, 9 | 100 > 81 | Acute - the biggest angle is under 90° |
| 6, 8, 11 | 100 < 121 | Obtuse - the biggest angle is over 90° |
To test any three sides quickly, enter the two shorter ones into the calculator on this page and compare the hypotenuse it returns against your third side: a match means a right triangle.