Annulus Calculator
Find area and total inner-plus-outer boundary of a circular ring.
Your numbers
Ring area
Use consistent units. The result follows the assumptions you enter.
Scenario comparison
Up to three snapshots in this tab. Loading one replaces the current inputs.
Formula
Use A = π(R²−r²) and P = 2π(R+r). R and r are outer and inner radii in the same unit. A is annular area; P includes both boundary circles.
Find area and total inner-plus-outer boundary of a circular ring.
Worked example
- Outer radius (m)
- 5
- Inner radius (m)
- 2
- Ring area
- 65.9734457254 m²
- Total boundary
- 43.9822971503 m
Scope and limitations
Use consistent units. The result follows the assumptions you enter.
Inputs are checked for missing values and allowed ranges. A result outside the finite numeric range is not displayed. Rounding affects display, while the calculation uses the model’s numeric precision.
Check your units and assumptions before relying on a result. Changing a label does not convert a currency or physical unit.
Formula version: c1bcf29f193e · Example checked: