# ABC Triangle Calculator

Using the ABC triangle calculator, you can calculate the right triangle sides, or calculate the right triangle angles. From the known values of sides / angles / area, you will be able to find all missing measurements in the right triangle!

## What is a right triangle?

A right triangle is any **triangle that satisfies the Pythagorean theorem**. As per the Pythagorean theorem, the **square of the largest side** must be **equal to** the **sum of squares of the other two sides** in a right triangle. Any triangle that satisfies this condition will be a right-angled triangle.

For example, consider a triangle with side lengths 3, 4 and 5. Here, the square of the largest side (5) is 25. The sum of squares of the other 2 sides is 9 + 16, which also gives us 25. Therefore, a triangle with side lengths 3, 4 and 5 units will be a right-angled triangle, and these numbers (3, 4, 5) are said to form a Pythagorean triplet.

**Pythagorean theorem**

For more on the theorem, you can head over to our pythagorean theorem calculator, pythagorean triple calculator, and pythagoras triangle calculator.

## How do I use the ABC triangle calculator?

To use the ABC triangle calculator, you need to know one of the following, for a right triangle:

- Two sides of the right triangle;
- One acute angle and one side of the right triangle; or
- Area and one side of the right triangle.

Depending on your available measurements, do the following:

- Choose a preferred combination of input measurements.
- Key in the values.
- The ABC triangle calculator will automatically calculate all the other unknown measurements in the triangle!

## Other right triangle calculators

If you found this tool useful in calculating the right triangle angles and sides, you might also want to take a look at some of our other right triangle calculators listed below:

## FAQ

### Does 4-5-6 make a right triangle?

**No**, a triangle with side lengths 4, 5 and 6 units will not form a right triangle, because these numbers don't satisfy the Pythagorean theorem. We can verify it as follows:

- The square of the largest side (6) is 36.
- The square of 4 is 16.
- The square of 5 is 25.
- The sum of 16 and 25 is 41, which is not equal to 36. So these lengths will not form a right-angled triangle.

### Is 1-2-3 a Pythagorean triplet?

**No**, the numbers 1, 2, and 3 do not form a Pythagorean triplet because they fail the condition for the Pythagorean theorem. The sum of squares of 1 and 2 (1 + 4) is 5, and it is not equal to the square of 3 (9).