Hypotenuse Calculator

Calculate the hypotenuse of a right triangle using the Pythagorean theorem

Enter the lengths of two sides of a right triangle to calculate the hypotenuse. This calculator uses the Pythagorean theorem (a² + b² = c²) for accurate results.

Examples

Click on any example to load it into the calculator

Classic 3-4-5 Triangle

Find Hypotenuse (c)

The most famous Pythagorean triple

Side A: 3

Side B: 4

Unit: unitless

Construction Example

Find Hypotenuse (c)

Finding diagonal brace length for a rectangular frame

Side A: 12

Side B: 9

Unit: feet

Find Missing Side A

Find Side A

Calculate unknown side when hypotenuse and one side are known

Side B: 8

Hypotenuse: 10

Unit: meters

Screen Diagonal

Find Hypotenuse (c)

Calculate diagonal length of a rectangular screen

Side A: 1920

Side B: 1080

Unit: unitless

Other Titles
Understanding Hypotenuse Calculator: A Comprehensive Guide
Master the Pythagorean theorem and learn how to calculate hypotenuse lengths for right triangles in various real-world applications

What is a Hypotenuse? Mathematical Foundation and Properties

  • The hypotenuse is the longest side of a right triangle
  • It is always opposite to the right angle (90-degree angle)
  • Fundamental to the Pythagorean theorem and geometric calculations
The hypotenuse is the longest side of a right triangle, positioned opposite to the right angle. It serves as a fundamental element in geometry and trigonometry, connecting the two perpendicular sides (legs) of the triangle through the famous Pythagorean theorem.
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: a² + b² = c². This relationship has been known for over 2,500 years and remains one of the most important mathematical principles.
Understanding the hypotenuse is crucial for solving problems in construction, navigation, engineering, and many other fields. It allows us to find unknown distances, verify right angles, and calculate areas and perimeters of triangular structures.
The term 'hypotenuse' comes from the Greek word 'hypoteinousa,' meaning 'stretching under.' This reflects how the hypotenuse stretches underneath the right angle, forming the triangle's foundation.

Basic Hypotenuse Examples

  • In a 3-4-5 triangle: 3² + 4² = 9 + 16 = 25 = 5²
  • For a square with side length 1, the diagonal (hypotenuse) = √2 ≈ 1.414
  • A ladder leaning against a wall forms the hypotenuse of a right triangle
  • TV screen diagonals are measured as the hypotenuse of the rectangular screen

Step-by-Step Guide to Using the Hypotenuse Calculator

  • Master different calculation modes for various triangle problems
  • Understand input validation and measurement units
  • Interpret results and apply them to real-world scenarios
Our hypotenuse calculator offers three distinct calculation modes to solve different types of right triangle problems efficiently and accurately.
Calculation Modes:
  • Find Hypotenuse: Enter both legs (sides A and B) to calculate the hypotenuse using c = √(a² + b²)
  • Find Side A: Enter side B and hypotenuse to calculate the missing side A using a = √(c² - b²)
  • Find Side B: Enter side A and hypotenuse to calculate the missing side B using b = √(c² - a²)
Input Guidelines:
  • Positive Numbers Only: All measurements must be positive values greater than zero
  • Decimal Support: The calculator accepts decimal values for precise measurements
  • Unit Selection: Choose appropriate units (meters, centimeters, inches, feet, or unitless) for consistent results
Result Interpretation:
  • Primary Result: The calculated length with appropriate precision
  • Triangle Area: Calculated as (1/2) × side A × side B for additional context
  • Perimeter: Sum of all three sides for complete triangle analysis

Practical Usage Examples

  • Input: a=6, b=8 → Hypotenuse = 10 (perfect Pythagorean triple)
  • Input: hypotenuse=13, b=5 → Side A = 12 (another Pythagorean triple)
  • Roof calculation: width=8m, height=6m → Rafter length = 10m
  • Cable installation: horizontal=50ft, vertical=30ft → Cable length = 58.31ft

Real-World Applications of Hypotenuse Calculations

  • Construction and Architecture: Roof design, structural bracing
  • Navigation and Surveying: Distance calculations, positioning
  • Technology and Design: Screen dimensions, component sizing
  • Sports and Recreation: Field layouts, equipment specifications
Hypotenuse calculations are essential across numerous industries and daily activities, providing practical solutions for design, construction, and problem-solving:
Construction and Architecture:
  • Roof Design: Calculate rafter lengths for gabled roofs using building width and desired pitch
  • Structural Bracing: Determine diagonal brace lengths for rectangular frames and trusses
  • Foundation Layout: Verify right angles using the 3-4-5 method or similar proportional triangles
Navigation and Surveying:
  • Distance Measurement: Calculate straight-line distances when only horizontal and vertical components are known
  • GPS Navigation: Determine actual travel distance considering elevation changes
  • Property Surveying: Establish property boundaries and lot dimensions accurately
Technology and Manufacturing:
  • Screen Specifications: Calculate diagonal measurements for monitors, TVs, and mobile devices
  • Component Design: Size diagonal elements in mechanical assemblies and electronic housings
  • Quality Control: Verify manufactured parts meet geometric specifications

Industry Applications

  • Roof: 24ft span, 8ft rise → Rafter length = 25.3ft per side
  • Ladder safety: 20ft ladder, 4ft from wall → Reaches 19.6ft height
  • TV size: 55" diagonal screen = 47.9" × 27.0" (16:9 aspect ratio)
  • Baseball diamond: 90ft bases → Diagonal distance = 127.3ft

Common Misconceptions and Correct Calculation Methods

  • Avoiding errors in triangle identification and measurement
  • Understanding when the Pythagorean theorem applies
  • Recognizing special triangles and their properties
Understanding common mistakes and misconceptions helps ensure accurate hypotenuse calculations and proper application of the Pythagorean theorem.
Common Misconceptions:
  • All Triangles: The Pythagorean theorem only applies to RIGHT triangles, not all triangles
  • Any Side: The hypotenuse must be the LONGEST side; it cannot be shorter than either leg
  • Unit Mixing: All measurements must use the same units for accurate calculations
Verification Methods:
  • Triangle Inequality: Check that the sum of any two sides is greater than the third side
  • Right Angle Test: Verify that a² + b² = c² exactly for the given measurements
  • Physical Validation: Use measuring tools to confirm theoretical calculations in practice
Special Cases and Considerations:
  • Pythagorean Triples: Recognize common integer combinations like 3-4-5, 5-12-13, and 8-15-17
  • Isosceles Right Triangles: In 45-45-90 triangles, hypotenuse = leg × √2
  • Precision Limits: Understand rounding effects and measurement accuracy limitations

Common Errors and Solutions

  • Invalid: 2, 3, 6 (violates triangle inequality: 2 + 3 < 6)
  • Valid: 5, 12, 13 (perfect Pythagorean triple: 5² + 12² = 13²)
  • Square diagonal: side = 10, diagonal = 10√2 ≈ 14.14
  • Measurement error: 3.01, 4.02, 5.03 ≈ valid triangle (accounting for precision)

Mathematical Derivation and Advanced Applications

  • Understanding the proof and origin of the Pythagorean theorem
  • Extensions to three-dimensional calculations and coordinates
  • Integration with trigonometry and advanced geometry
The mathematical foundation of hypotenuse calculations extends beyond basic applications into advanced geometric and trigonometric concepts.
Mathematical Proof and Derivation:
The Pythagorean theorem can be proven through multiple methods, including geometric rearrangement, algebraic manipulation, and similarity relationships. The most intuitive proof involves arranging four identical right triangles around a square.
For a right triangle with legs a and b, and hypotenuse c: The area of the large square equals (a + b)². This same area can be calculated as 4 × (½ab) + c², leading to the relationship a² + b² = c².
Three-Dimensional Extensions:
In three dimensions, the distance formula extends the Pythagorean theorem: d = √[(x₂-x₁)² + (y₂-y₁)² + (z₂-z₁)²]. This calculation finds the straight-line distance between any two points in 3D space.
Space diagonals of rectangular prisms use this principle: for a box with dimensions a, b, and c, the space diagonal equals √(a² + b² + c²).
Trigonometric Relationships:
In right triangles, trigonometric functions relate angles to side ratios: sin(θ) = opposite/hypotenuse, cos(θ) = adjacent/hypotenuse, tan(θ) = opposite/adjacent. These relationships enable angle calculations when side lengths are known.
The law of cosines generalizes the Pythagorean theorem for any triangle: c² = a² + b² - 2ab×cos(C), where C is the angle opposite side c.

Advanced Mathematical Applications

  • 3D distance: Point (0,0,0) to (3,4,5) = √(3² + 4² + 5²) = √50 ≈ 7.07
  • Box diagonal: 6×8×10 box has space diagonal = √(6² + 8² + 10²) = √200 ≈ 14.14
  • Angle calculation: 3-4-5 triangle has angles ≈ 36.87°, 53.13°, 90°
  • Law of cosines: Triangle with sides 5, 7, 10 and angle 60° between sides 5 and 7