What is the formula for the area of a right triangle?

Area = (base × height) / 2. Because the two legs of a right triangle are perpendicular to each other, they act directly as the base and the height — no additional perpendicular drop is needed.

How is the hypotenuse calculated?

The hypotenuse c is found using the Pythagorean theorem: c = √(base² + height²). It is always the longest side and lies opposite the right angle.

What units does this calculator use?

The calculator is unit-agnostic. Enter lengths in any consistent unit (meters, feet, inches, centimeters). The area result will be in the corresponding square unit (e.g., square meters if you entered meters).

Does the order of base and height matter?

No. Area = (base × height) / 2 is symmetric, so swapping the two legs gives the same area. Only the diagram will flip orientation.

Can I enter decimal values?

Yes. The calculator accepts any positive decimal number for both legs. Results are rounded to six significant figures to avoid floating-point noise.

What is the perimeter of a right triangle?

The perimeter is the sum of all three sides: base + height + hypotenuse. This calculator computes it automatically once both legs are entered.

What if I only know the hypotenuse and one leg?

Use the Pythagorean theorem to find the missing leg: missing leg = √(hypotenuse² − known leg²). Then enter both legs here to get the area.

Area of a Right Triangle Calculator

Enter the two legs (base and height) of a right triangle to get the area, hypotenuse, and perimeter instantly with a visual diagram.

Enter the Two Legs

Base (horizontal leg)

units

Height (vertical leg)

units

Formulas

Area (b × h) / 2

Hypotenuse √(b² + h²)

Perimeter b + h + hypotenuse

Enter both legs on the left to see results

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Summary

This calculator finds the area, hypotenuse, and perimeter of a right triangle from its two legs (base and height). The formula Area = (base × height) / 2 applies because the two legs are perpendicular, making one the base and the other the height. A live SVG diagram updates as you type, showing the right-angle marker, labeled sides, and the 90-degree corner.

How it works

Enter the length of the base (horizontal leg) in the first field.
Enter the length of the height (vertical leg) in the second field.
The area, hypotenuse, and perimeter are calculated instantly.
The SVG diagram updates to reflect the proportions of your triangle.
Click "Copy Result" to copy the area value to your clipboard.

Use cases

Calculate the floor area of a triangular corner room or alcove.
Find the material needed for a right-triangle roof section or gable.
Solve geometry homework involving right triangles.
Verify Pythagorean theorem results by checking the hypotenuse.
Estimate fabric or tile cuts for diagonal right-triangle shapes.
Determine land area of triangular plots with a right-angle boundary.
Check engineering calculations for ramps and sloped structures.
Teach or learn the relationship between legs, hypotenuse, and area.

Frequently Asked Questions

Last updated: 2026-05-28 · Reviewed by Nham Vu