Enter Known Values
Sides
Angles
Reference Guide
Example: 3-4-5 right triangle
Enter any known values above to calculate the rest
Side A
-
Side B
-
Side C
-
Angle A
-
Angle B
-
Area
-
Perimeter
-
How to Use This Calculator
Enter any two known values (sides or angles) of your right triangle, then click the Calculate button to compute all the remaining values. The calculator uses the Pythagorean theorem and trigonometric functions to solve for unknown sides and angles. You can also press Enter after typing a value for quick calculation.
Formulas Used:
- Pythagorean Theorem: a² + b² = c²
- Sine: sin(angle) = opposite / hypotenuse
- Cosine: cos(angle) = adjacent / hypotenuse
- Tangent: tan(angle) = opposite / adjacent
- Area: ½ × base × height
- Perimeter: a + b + c
Calculating Right Triangles
a² + b² = c²
The Pythagorean theorem states that in a right triangle, the square of the hypotenuse (c) equals the sum of squares of the other two sides. Enter any two sides in the calculator above to find the third!
Triangle Area
Area = ½ × b × h
The area of a right triangle is half the product of its base and height. Our calculator automatically computes this when you enter two sides. Try it above!
Finding Angles
sin θ = opp/hyp
cos θ = adj/hyp
tan θ = opp/adj
Trigonometric functions help find angles from sides. Enter any two values in the calculator above, and it will instantly compute all angles using sine, cosine, and tangent.
Frequently Asked Questions
How do I find the hypotenuse of a right triangle?
Use the Pythagorean theorem: c = √(a² + b²). Enter the two legs (sides a and b) in our calculator, and it will calculate the hypotenuse (side c) automatically.
What is the relationship between the angles in a right triangle?
The three angles in any triangle always sum to 180°. Since a right triangle has one 90° angle, the other two angles must sum to 90°. These are called complementary angles.
How do I calculate the area of a right triangle?
The area of a right triangle is: Area = (1/2) × base × height. For right triangles, the two legs serve as the base and height, making the formula: Area = (1/2) × a × b.
Learn More About Trigonometry
Deepen your understanding of right triangles and trigonometry with these excellent educational resources:
Khan Academy - Basic Trigonometry
Free comprehensive video lessons and practice problems covering all aspects of right triangle trigonometry.
Visit Khan Academy →Math is Fun - Trigonometry
Interactive explanations with visual demonstrations, making complex trigonometric concepts easy to understand.
Explore Math is Fun →