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Pythagorean theorem calculator

Find any side of a right triangle — hypotenuse or leg — from the two you know, with the three squares drawn.

Related tools

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Perimeter calculatorCompute the perimeter of a rectangle, square, circle or triangle.Equilateral triangle calculatorCompute the area, height and perimeter of an equilateral triangle from its side.Triangle area calculator (Heron's formula)Compute a triangle's area from the length of its three sides.Hexagon area calculatorCompute the area of a regular hexagon from its side length.Pentagon area calculatorCompute the area of a regular pentagon from its side length.Regular polygon area calculatorCompute the area of a regular polygon from its number of sides and side length.Square diagonal calculatorCompute the diagonal and area of a square from its side length.Trapezoid area calculatorCompute the area of a trapezoid from its two parallel sides and height.

Enter Side a, Side b and the Pythagorean theorem calculator works out Hypotenuse (c), Triangle area straight away. For instance, with Side a = 3 and Side b = 4 it returns Hypotenuse (c) = 5 and Triangle area = 6.

How to use it

  1. Enter your values: Side a, Side b.
  2. Read the result instantly: Hypotenuse (c), Triangle area.

Frequently asked questions

How does the Pythagorean theorem calculator work?

It takes Side a and Side b and derives Hypotenuse (c) and Triangle area from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

2 values: Side a and Side b. Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Side a = 3 and Side b = 4, the calculator returns Hypotenuse (c) = 5 and Triangle area = 6. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

How much does the result change with different inputs?

It moves a lot. Using Side a = 6 and Side b = 8 instead, Hypotenuse (c) goes from 5 to 10 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Side a = 2 and Side b = 2, Hypotenuse (c) comes out at 2.828. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Homework and site work alike: how much paint a wall takes, how much water a tank holds, whether a corner is square — and, on the coordinate side, the slope between two points, the distance across a plan, the midpoint of a span.

What is the most common mistake?

Mixing units inside one shape. Entering a length in centimetres and a width in metres gives an area wrong by a factor of a hundred, and the result looks perfectly plausible.

What is the difference between the Pythagorean theorem calculator and the Perimeter calculator?

This one returns Hypotenuse (c) and Triangle area; the Perimeter calculator returns Perimeter. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Equilateral triangle calculator is the closest one after this: Compute the area, height and perimeter of an equilateral triangle from its side.

What else is worth having open alongside it?

Triangle area calculator (Heron's formula) and Hexagon area calculator — they come up in the same task often enough to be worth a second tab.

Further reading

All guides →
ExplainerThe Pythagorean Theorem ExplainedIn a right triangle, a² + b² = c². Here's what the formula means, a worked example, how to find any side, and where it's used in real life.How-toHow to Calculate VolumeVolume is the space inside a shape. Here's how to find it for boxes, cylinders and spheres, and why keeping your units consistent is the whole game.How-toCircle: Circumference and AreaCircumference is 2πr, area is πr². Here's how radius, diameter and π fit together, both formulas worked through, and how not to mix them up.How-toHow to Find the Area of a Triangle: Base × Height and Heron's FormulaTwo reliable ways to find a triangle's area: half base times height when you know the height, and Heron's formula when you only know the three sides.ExplainerThe Flat Pattern of a Cone Is a Sector, Not a CircleRoll a 50 mm cone 80 mm tall and its pattern is a 190.8° slice of a 94 mm circle. Flatten a nearly cylindrical lampshade and the pattern radius runs to 839 mm — the shallower the taper, the further away the apex.How-toHow to Find the Distance Between Two PointsUse the distance formula d = √((x₂−x₁)² + (y₂−y₁)²) to measure the straight-line distance between two points on a plane, with a worked example and the midpoint too.