Right Triangle Calculator Online
Solve a right triangle from any two sides or a side and an angle. Sides, angles, area, and perimeter are computed instantly in your browser.
The Right Triangle Calculator runs entirely in your browser. The side lengths and angles you enter are computed locally and never leave your device.
Open the Pythagorean Theorem Calculator
About Right Triangle Calculator
The Right Triangle Calculator solves a right triangle from any two known values — two of the legs and the hypotenuse, or one side plus an acute angle. Enter leg a, leg b, hypotenuse c, angle A (opposite a), or angle B (opposite b): fill in any two and the calculator uses the Pythagorean theorem and basic trigonometry to fill in the rest, along with the triangle's area and perimeter. It flags entries that cannot form a real right triangle, such as a hypotenuse shorter than a given leg. It is useful for geometry homework, framing and construction layouts, roof pitch and ramp angle checks, ladder and screen-diagonal problems, and any situation where two measurements of a right angle are known and a third is needed. Everything runs locally — numbers are computed in your browser and nothing is uploaded.
Features
- Solve for any missing side or angle from two known values
- Accepts two legs, a leg and the hypotenuse, or a side plus an acute angle
- Uses the Pythagorean theorem (a² + b² = c²) for side-only inputs
- Uses sine, cosine, and tangent when an angle is one of the two known values
- Computes both acute angles automatically, since they always sum to 90°
- Reports triangle area and perimeter alongside the solved sides
- Flags impossible combinations, like a hypotenuse shorter than a leg
- Runs entirely in your browser with no measurements sent anywhere
How to use the Right Triangle Calculator
- Enter any two known values: two sides, or a side and an angle
- Leave the remaining fields blank so the calculator solves them
- Review the solved sides, angles, area, and perimeter
- Copy the full result set with one click
Example
Input
a=3, b=4
Output
c=5 · area 6
Two legs solve the hypotenuse, both angles, area, and perimeter at once.
Common errors & troubleshooting
- The calculator shows 'the hypotenuse must be longer than each leg.' — The hypotenuse c is always the longest side of a right triangle. Double-check you did not swap a leg value into the hypotenuse field.
- Angle field rejects the entered value. — Angles must be between 0 and 90 degrees, since both non-right angles in a right triangle are acute. Enter the angle in degrees, not radians.
- Three side lengths were entered and the result looks wrong. — If a, b, and c are all filled in, they must satisfy a² + b² = c² exactly. Clear one field and let the calculator solve it instead of entering all three yourself.
- Only one value is filled in and nothing is calculated. — The calculator needs two known values to solve a triangle — fill in a second side or angle field.
Frequently asked questions
- What values does the Right Triangle Calculator need?
- Any two of: leg a, leg b, hypotenuse c, angle A (opposite a), or angle B (opposite b). Given two sides, or one side and one acute angle, the calculator solves everything else.
- How does the Right Triangle Calculator find a missing side?
- When two sides are known it applies the Pythagorean theorem, a² + b² = c². When a side and an angle are known it uses sine, cosine, or tangent of that angle instead.
- Why do angle A and angle B always add up to 90 degrees?
- A right triangle's third angle is the right angle itself, fixed at 90°. Since all three angles of any triangle sum to 180°, the two remaining acute angles A and B always add up to 90°.
- Can the right triangle calculator find the area and perimeter?
- Yes. Once the three sides are solved, the calculator reports the area (half the product of the two legs) and the perimeter (the sum of all three sides) automatically.
- Why does the calculator reject some side combinations?
- If the hypotenuse you enter is not longer than a given leg, or three entered sides do not satisfy a² + b² = c², the values cannot form a real right triangle, so the calculator shows an error instead of a wrong answer.
- Does the Right Triangle Calculator upload my measurements?
- No. The Right Triangle Calculator runs entirely in your browser. The numbers you enter are never uploaded to ArrayKit.
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