# Annulus Calculator

Use our online inner and outer circle calculator to calculate the inner and outer circumference of an annulus, surface area of inner circle and outer circle and annulus. Annulus is a ring-shaped object bounded by two concrete circle with the same center. Area of the annulus is the difference between the areas of the outer and inner circle of radius. Enter the radius of inner and outer circle in the below annulus calculator to find the resultant value.

## Inner and Outer Circle Calculator

Use our online inner and outer circle calculator to calculate the inner and outer circumference of an annulus, surface area of inner circle and outer circle and annulus. Annulus is a ring-shaped object bounded by two concrete circle with the same center. Area of the annulus is the difference between the areas of the outer and inner circle of radius. Enter the radius of inner and outer circle in the below annulus calculator to find the resultant value.

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### Example:

Derive calculation of an annulus with an inner circle radius of about 8 cm and outer circle radius of about 9 cm.
Inner Circumference of an Annulus = 2 × π × 8

=50.2655cm.

Outer Circumference of an Annulus = 2 × π × 9

= 56.5487 cm.

Surface Area of the Inner Circle = π × 8 × 8

=201.0619 cm^{2}

Surface Area of the Outer Circle = π × 9 × 9

= 254.469 cm^{2}

Surface Area of the Annulus = π × ((9 × 9) - (8 × 8))

= 53.4071 cm^{2}