CalcVind

Right Triangle Calculator

Solve any right-angled triangle from two values

What do you know?

C is the right angle; c is the hypotenuse; angle A is opposite side a.

Solved Triangle

3Side a
4Side b
5Hypotenuse c
36.8699°
Angle A
53.1301°
Angle B
6
Area
12
Perimeter
2.4
Height to c

Working

  1. c = √(a² + b²) = √(9 + 16) = 5
  2. A = tan⁻¹(a ÷ b) = 36.869898°, B = 90° − A = 53.130102°
  1. 1
    Choose what you know
    Two sides, or a side and an angle
  2. 2
    Enter the values
    Any length unit works
  3. 3
    Get every side and angle
    Plus area, perimeter and working

Right triangle formulas

In a right triangle the sides and angles are linked by Pythagoras and by SOH-CAH-TOA:

a² + b² = c²

sin A = a ÷ c (opposite ÷ hypotenuse)

cos A = b ÷ c (adjacent ÷ hypotenuse)

tan A = a ÷ b (opposite ÷ adjacent)

A + B = 90°

Which side is which?

The hypotenuse c is always the longest side, opposite the right angle. Angle A sits opposite side a, and angle B opposite side b. Swap a and b if your diagram labels them the other way round.

Special right triangles

A 30-60-90 triangle has sides in the ratio 1 : √3 : 2, and a 45-45-90 triangle has sides 1 : 1 : √2. The 3-4-5 triangle is the simplest one with whole-number sides.

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Frequently asked questions

How do I find the hypotenuse?

Square both legs, add them, and take the square root: c = √(a² + b²). With legs 3 and 4, the hypotenuse is 5.

How do I find an angle from two sides?

Use the inverse trig functions. With the opposite side a and adjacent side b, A = tan⁻¹(a ÷ b).

How do I find the area of a right triangle?

Half the product of the two legs: area = a × b ÷ 2.

Last reviewed: October 2026