DIY Cost Tools
Pythagorean Theorem Calculator
GEOMETRY CALCULATOR
Solve for a missing side of a right triangle using two known side lengths.
Missing sidec = 5
Smaller acute angle36.8699°
Larger acute angle53.1301°
Area6 square units
How it works
For a right triangle, the square of the hypotenuse equals the sum of the squares of the two legs. Rearranging the formula solves for either missing leg.
Formula
a² + b² = c², where c is the hypotenuse.
Example
With legs 3 and 4, c = √(3² + 4²) = 5. The triangle’s area is 3 × 4 ÷ 2 = 6 square units.
Important limits
- The formula applies only to right triangles.
- The hypotenuse must be longer than either leg.
- Angles are derived from the side lengths and rounded for display.
Frequently asked questions
Which side is the hypotenuse?
It is the side opposite the 90-degree angle and is always the longest side.
Can this find triangle area?
Yes. For a right triangle, area equals one-half of the product of the legs.
Review notes
Calculations follow the Pythagorean theorem and right-triangle trigonometry. Last reviewed September 30, 2026.