Arc Length Calculator

Calculate arc length, sector area, and chord length with support for degrees and radians

Max: 360°

Arc Length Formulas

Arc Length (Degrees):

Arc = (θ/360) × 2πr

Where θ is in degrees and r is radius

Example: (90/360) × 2π × 10 = 15.71 units

Arc Length (Radians):

Arc = r × θ

Where θ is in radians - the simplest formula!

Example: 10 × 1.571 = 15.71 units

Sector Area:

Area = (1/2) × r² × θ (radians)

Or: Area = (θ/360) × πr² (degrees)

Example: (1/2) × 10² × 1.571 = 78.54 square units

Chord Length:

Chord = 2r × sin(θ/2)

Straight-line distance between arc endpoints

Example: 2 × 10 × sin(0.7855) = 14.14 units

History

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Pro Tips

  • π radians = 180 degrees
  • Arc length is always longer than chord length
  • Full circle arc = 2πr (circumference)
  • Radians make formulas simpler in calculus
  • Common in physics for angular motion

Common Conversions

30° = π/6
≈ 0.524 radians
45° = π/4
≈ 0.785 radians
90° = π/2
≈ 1.571 radians
180° = π
≈ 3.142 radians

Frequently Asked Questions

What is arc length and how do you calculate it?

Arc length is the distance along the curved line of a circle between two points. Calculate it using: Arc = (θ/360) × 2πr for degrees, or Arc = rθ for radians, where r is radius and θ is the central angle. For example, with radius 5 and angle 60°: Arc = (60/360) × 2π × 5 = 5.24 units.

What is the difference between degrees and radians?

Degrees and radians are two ways to measure angles. A full circle is 360° or 2π radians. To convert: degrees to radians multiply by π/180, radians to degrees multiply by 180/π. For example, 90° = π/2 radians ≈ 1.571 radians. Radians are often used in calculus and physics.

How do you find the sector area from arc length?

The sector area formula is: Area = (1/2) × r × arc length, or Area = (θ/360) × πr² for degrees. For a radius of 10 and arc length of 15.71, the area is (1/2) × 10 × 15.71 = 78.54 square units. This works because the sector is a fraction of the full circle.

What is chord length and how does it relate to arc length?

Chord length is the straight-line distance between the endpoints of an arc, while arc length is the curved distance. Calculate chord using: Chord = 2r × sin(θ/2), where θ is in radians. The chord is always shorter than the arc except when the arc is a straight line (180°).

What Our Users Say

"Essential tool for road design and circular curves. The ability to work in both degrees and radians is perfect for my work. Calculations are always accurate and the export feature is great for documentation."

Michael Chen
Civil Engineer

"My students love this calculator for circular motion problems! The visual comparison chart helps them understand the relationship between arc length, chord length, and sector area. Highly recommended for education."

Jennifer Williams
Physics Teacher

"Perfect for designing curved architectural elements. I use it daily for calculating arched doorways, curved walls, and circular features. The history feature is super convenient for comparing different designs."

Alex Martinez
Architect