Right Triangle Calculator
Right angle at C — sides a, b, hypotenuse c plus angles A and B. Click any i for detail.
Triangle
Known
i
Known
Two legs, a leg and hypotenuse, or an acute angle plus one side. |
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|---|---|
Leg a
i
a
Side opposite angle A. |
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Leg b
i
b
Side opposite angle B. |
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Leg a
i
a
Opposite A. |
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Hypotenuse c
i
c
Must be longer than a. |
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Leg b
i
b
Opposite B. |
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Hypotenuse c
i
c
Must be longer than b. |
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Angle A (°)
i
A
Acute angle opposite a. |
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Side given
i
Which
Which length you know, relative to A. |
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Length
i
Length
Length of the side you picked. |
How to use this calculator
- Pick what you know: two legs, a leg and hypotenuse, or an angle plus one side.
- Enter those measurements.
- Read all sides, both acute angles, and area.
- Keep the right angle at C in the labeling used here.
Results explained
Uses Pythagoras and trig. The Pythagorean-only page fills one missing side; this page also solves angles and area.
Quick reference: right triangle
3-4-5 is the classic integer triple.
| Item | Detail |
|---|---|
| Pythagoras | a² + b² = c² |
| sin A | opposite/hyp = a/c |
| cos A | adjacent/hyp = b/c |
| Area | ab/2 |
Obtuse or oblique triangles are not solved here.
How the estimate is built
c = √(a²+b²); A = atan(a/b); B = 90° − A.
Example scenario
a=3, b=4 → c=5, A≈36.87°.
FAQ
Which side is c?
Hypotenuse opposite the right angle, longest side.
Can I enter an angle in radians?
This page uses degrees for angle inputs and outputs.
What if a²+b² < c²?
Not a valid right triangle; inputs are rejected or clamped.