Circle Length Calculator

Calculate radius, diameter, and circumference length relationships with step-by-step formulas

Calculate Circle Length Properties

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Circle Length Properties

Radius (r)
0 cm
Distance from center to edge
Diameter (d)
0 cm
Distance across the circle
Circumference (c)
0 cm
Length around the circle
Half Circle Length
0 cm
Length of semicircle perimeter

Circle Length Formulas

Basic Relationships:
d = 2r
r = d/2
c = 2πr
From Circumference:
r = c/(2π)
d = c/π
Half circle = πr
π (pi) ≈ 3.14159265359

Example Calculation

Circle Length Problem

Problem: Find the radius of a circle with 10 cm circumference.

Given: Circumference (c) = 10 cm

Solution

Formula: r = c/(2π)

Substitute: r = 10 cm / (2π)

Calculate: r = 10 / (2 × 3.14159) = 1.5915 cm

Diameter: d = 2r = 2 × 1.5915 = 3.1831 cm

Circle Length Relationships

r

Radius

Half the diameter

r = d/2 = c/(2π)

d

Diameter

Twice the radius

d = 2r = c/π

c

Circumference

Perimeter of circle

c = 2πr = πd

½

Half Circle

Semicircle perimeter

c_half = πr = πd/2

Quick Conversion Tips

To find radius:
From diameter: r = d ÷ 2
From circumference: r = c ÷ (2π)
To find diameter:
From radius: d = r × 2
From circumference: d = c ÷ π
To find circumference:
From radius: c = 2 × π × r
From diameter: c = π × d
Remember:
π ≈ 3.14159 (use for calculations)

Understanding Circle Length Relationships

What is Circle Length?

Circle length typically refers to the circumference - the distance around the perimeter of a circle. It's directly related to the radius and diameter through the fundamental relationship involving π (pi).

Key Measurements

  • Radius (r): Distance from center to any point on the circle
  • Diameter (d): Distance across the circle through the center
  • Circumference (c): Distance around the circle's perimeter
  • Half Circle: Semicircle perimeter length

Circle Length Formulas

Basic Formulas

c = 2πr
c = πd
d = 2r
r = d/2

Reverse Calculations

r = c/(2π)
d = c/π
Half circle = πr

Note: π (pi) is approximately 3.14159, representing the ratio of circumference to diameter for any circle.

Real-World Applications

  • • Wheel and tire sizing
  • • Pipe and conduit measurements
  • • Garden and landscape design
  • • Sports field layouts
  • • Engineering calculations

Common Examples

  • • Pizza diameter vs circumference
  • • Bicycle wheel measurements
  • • Clock face dimensions
  • • Swimming pool perimeters
  • • Circular table sizing

Measurement Tips

  • • Measure diameter for accuracy
  • • Use π = 3.14159 for precision
  • • Check units consistency
  • • Round appropriately
  • • Verify with known values