Toolstia / Pythagorean theorem calculator
Pythagorean theorem calculator
Enter any two sides of a right triangle and the third is found with a² + b² = c². You also get both acute angles, the area and the perimeter.
Fill in any two sides of a right triangle. c is the hypotenuse, the longest side.
How it works
- Fill in two of the three boxes.
- Leave the side you want to find empty.
- Read the missing side, the angles, the area and the perimeter.
The theorem
In a right triangle the square of the hypotenuse (the longest side, opposite the right angle) equals the sum of the squares of the other two sides.
Finding a leg
If you know the hypotenuse and one leg, the other leg is √(c² − a²). The hypotenuse must be longer than either leg.
Angles
Angle A = arctan(a ÷ b) and angle B = 90° − A.
Pythagorean triples
Whole-number sets such as 3-4-5, 5-12-13 and 8-15-17 work exactly.
Questions
Does it work for triangles without a right angle?
No. Use the triangle calculator for those.
Which side is the hypotenuse?
The longest side, opposite the 90° angle.
Is anything uploaded?
No. Your input stays in your browser and is never sent anywhere.