Calculate the area of an annulus, ring, or donut shape from outer radius and inner radius, outer diameter and inner diameter, or outer radius and ring width. Estimate square feet, square inches, square yards, square meters, circumference, waste, material quantity, and project cost.
Outer and inner radius mode:
The calculator finds the outer circle area, subtracts the inner circle area, and gives the remaining ring area.
Diameter mode:
The calculator divides the outer and inner diameters by 2 to get the radii, then calculates the annulus area.
Ring width mode:
The calculator subtracts the ring width from the outer radius to estimate the inner radius.
Area mode:
The calculator subtracts the inner circle area from the outer circle area and estimates the matching radii.
An annulus area calculator helps estimate ring-shaped spaces for circular walkways, pool decks, garden borders, fire pit rings, paver rings, landscaping, and construction layouts.
It can help calculate square footage, compare area units, estimate edge length, estimate material quantity, add waste, and estimate project cost.
Your result shows the annulus area, outer circle area, inner circle area, outer radius, inner radius, ring width, circumferences, total edge length, area with extra waste, estimated pieces or units needed, and estimated cost.
Square the outer radius, square the inner radius, subtract the inner value from the outer value, then multiply by pi. The formula is Area = π × (R² − r²).
An annulus is a ring-shaped area between two circles that share the same center, similar to a donut shape.
Divide the outer diameter and inner diameter by 2 to get the radii. Then use the annulus area formula with those radius values.
Ring width is the distance between the outer edge and inner edge. It equals outer radius minus inner radius.
Yes. Ring-shaped layouts often require curved cuts and trimming. For pavers, sod, landscaping fabric, tile, concrete, mulch fabric, or flooring, adding 5% to 15% extra is commonly helpful.