Pythagorean Theorem Calculator

1. Select Hypotenuse when Leg a and Leg b are known. Select Missing leg when Hypotenuse c and Leg b are known.
2. Enter a value in each visible field, then choose a label in Unit.
3. Click Calculate to show the missing side and the calculation steps.
4. Click Copy result or Download result (.txt) to keep the displayed text. Click Reset to clear the fields and restore the starting selections.

How the two calculation modes work

For a right triangle, the calculator uses a^2 + b^2 = c^2. Hypotenuse calculates c = sqrt(a^2 + b^2) from Leg a and Leg b. Missing leg calculates a = sqrt(c^2 - b^2) from Hypotenuse c and Leg b.

Leg a: 3
Leg b: 4
Unit: Unitless (plain numbers)
Result: Hypotenuse (c) = 5 units

Formula & steps lists the squared values, their sum or difference, and the square-root step. In the example, the calculator adds the squares of 3 and 4, then takes the square root of 25.

Input rules and unit labels

• Enter positive decimal-form numbers in the required fields. Blank values, letters, commas, signs, zero, negative values, and scientific notation fail validation.
• Each entered side must be no greater than 1e12. In Missing leg, Leg b must be shorter than Hypotenuse c.
• Unit includes Unitless (plain numbers), Millimeters (mm), Centimeters (cm), Meters (m), Kilometers (km), Inches (in), Feet (ft), Yards (yd), and Miles (mi).
• Unit labels the result only. Enter every side using the same unit because the calculator does not convert between units.

What appears after Calculate

After a valid calculation, the Result area shows the missing side, the known sides, and the selected unit label. Formula & steps shows each intermediate value. Changing a side, Unit, or solve mode hides the current result.

Reset clears all three side fields, selects Hypotenuse, and sets Unit to Unitless (plain numbers). The side-length arithmetic runs in the browser, and the calculator does not send the entered side lengths in a calculation request.

Keep the calculation with your notes

Copy result places the displayed calculation in the clipboard when copying succeeds. Download result (.txt) saves the same plain-text result as pythagorean-theorem-calculator-result.txt. The text includes the side values, selected unit label, and numbered steps.

If a copy attempt fails, the result text remains available for manual selection and copying. Reset removes the current result from view and clears the entered values.

When another calculator fits the input

Browse Math Calculators for Equations, Geometry & More when the task is not a right-triangle side calculation. Use Distance Formula Calculator for straight-line distance between coordinate points, and use Triangle Area Calculator when the target is triangle area from side, base-and-height, or coordinate inputs. Geometry Calculator is the better choice for slope, midpoint, circle measurements, polygon area, or common solid measurements.

Frequently asked questions