How to Calculate the Square Footage of a Circular Path or Garden Ring
A circular path — also called a garden ring or ring path — is the band of surface between two circles that share the same center. It is the shape of a stone walkway wrapping around a circular fire pit, fountain, tree or flower bed. You are not measuring the circle in the middle; you are measuring only the ring of pathway around it, which is why this needs its own calculation rather than a plain circle area.
The circular path formula
The area of the ring (an annulus) is the big circle minus the small circle:
Area = π × (R² − r²)
R is the outer radius of the whole feature, and r is the inner radius — the outer radius minus the width of the path. This calculator asks for the outer diameter and the path width, then works out both radii for you, so you never have to subtract circles by hand.
Measuring a circular path
- Outer diameter: Measure straight across the entire feature, passing through the center, from the outer edge of the path on one side to the outer edge on the other.
- Path width: Measure the width of the pathway itself — the distance from the inner edge (next to the fire pit or bed) to the outer edge.
The calculator subtracts the path width from the outer radius to find the inner radius. If you enter a path width larger than the radius, it flags the problem, since a path cannot be wider than the feature's radius.
Worked example
Suppose a gravel path rings a circular fire pit. The whole feature measures 20 feet across (outer diameter), and the path itself is 2 feet wide.
Outer radius R = 10 ft; inner radius r = 10 − 2 = 8 ft. Area = π × (10² − 8²) = π × (100 − 64) = π × 36 ≈ 113.10 square feet.
For gravel, multiply this by your chosen depth and add about 10% for the curved edge cuts and settling.
Where circular paths appear
- Garden walkways: Stone or gravel paths circling a fountain, statue or planted bed.
- Fire pit surrounds: A paved ring around a central fire pit.
- Tree rings: Mulch or paver rings around the base of a tree.
- Decorative borders: A contrasting band around a circular patio.
Related shape calculators
This is the landscaping-focused version of the ring (annulus) calculator — same math, framed for paths. For the solid circle in the middle, use the circle calculator. For a straight rectangular border instead of a round one, see the rectangle border calculator.