Pythagorean Theorem Calculator

Solve for any side of a right triangle using a2 + b2 = c2. Enter any two known values.

Result
0
a20
b20
c20

About Pythagorean Theorem Calculator

The Pythagorean Theorem Calculator solves for any side of a right triangle using the formula a² + b² = c². Choose whether you want to find the hypotenuse (c) or one of the legs (a or b), enter the two known side lengths, and the calculator computes the unknown side along with the squared values of all three sides. The Pythagorean theorem is one of the most fundamental relationships in geometry, with applications far beyond the classroom. Architects and construction workers use it to verify right angles and calculate diagonal lengths, navigation systems rely on it for distance calculations, and game developers use it for collision detection and movement physics. The tool uses precise square root computations and displays results to six decimal places. By showing the intermediate squared values (a², b², c²), it reinforces the underlying algebraic relationship. Whether you are a student proving geometric theorems, a carpenter checking if a corner is square, or a programmer implementing 2D distance calculations, this calculator makes right-triangle solutions immediate and intuitive.

When to Use This Calculator

Construction & Carpentry: Need to check if a corner is square? Measure 3 feet along one wall and 4 feet along the other. The diagonal should be exactly 5 feet if the corner is 90 degrees. This calculator lets you check any combination — not just the classic 3-4-5 triangle.

Home Improvement: Planning a diagonal fence across a rectangular yard that's 50 feet by 30 feet? The diagonal length is the hypotenuse: √(50² + 30²) = 58.31 feet. That tells you exactly how much fencing material to buy for the diagonal section.

Navigation & Mapping: If you walk 400 meters north and then 300 meters east, your straight-line distance from the starting point is √(400² + 300²) = 500 meters. This is just the Pythagorean theorem applied to coordinates, and it works for any right-angled path.

How to Use This Calculator

Say you're building a ramp and know the horizontal run is 8 feet and the vertical rise is 3 feet. You need to find the length of the ramp surface (the hypotenuse). Select "Hypotenuse (c)" from the dropdown, enter 8 for leg a and 3 for leg b, then Calculate. The result shows c = 8.544004 feet — that's how long your ramp board needs to be. The squared values show a² = 64, b² = 9, and c² = 73, confirming that 64 + 9 = 73. For the reverse, say you have a 10-foot ladder and want to place it 6 feet from a wall. Select "Leg (a)", enter c = 10 and b = 6. The result shows leg a = 8 feet — that's how high up the wall the ladder reaches.

Frequently Asked Questions

Does the Pythagorean theorem only work for right triangles?

Yes, a² + b² = c² only applies to right triangles where one angle is exactly 90 degrees. For non-right triangles, you'd need the law of cosines: c² = a² + b² - 2ab×cos(C). If you plug three side lengths into this calculator and the squared values don't add up, the triangle isn't right-angled.

How do I find the hypotenuse?

To find the hypotenuse (the longest side opposite the right angle), use c = √(a² + b²). For example, if leg a = 3 and leg b = 4, the hypotenuse is √(3² + 4²) = √(9+16) = √25 = 5. Select "Hypotenuse (c)" from the dropdown, enter both legs, and the calculator does this instantly.

Can I use the Pythagorean theorem for any triangle?

No, the Pythagorean theorem only works for right triangles. For non-right triangles (acute or obtuse), use the law of cosines: c² = a² + b² - 2ab·cos(C). If you attempt to use the Pythagorean theorem on a non-right triangle, the squared values will not balance, confirming it's not right-angled.

What is a Pythagorean triple?

A Pythagorean triple consists of three positive integers (a, b, c) that satisfy a² + b² = c². The most famous is (3, 4, 5). Other examples include (5, 12, 13), (8, 15, 17), and (7, 24, 25). These represent right triangles with integer side lengths and are useful for quick construction layout.

How is the Pythagorean theorem used in real life?

It's used in construction to ensure square corners (3-4-5 method), in navigation to calculate shortest distances, in carpentry for diagonal cuts, in computer graphics for distance calculations between points, in GPS for positioning, and in telecommunications for signal range coverage areas.