Annular / Donut Concrete Volume Calculator (Metric Units)
The Circular Ring (Donut) Concrete Calculator - Metric determines ready-mix requirements for annular slabs such as ring footings, tank pads, maintenance hole collars, and pipe supports. By entering the outer diameter, inner diameter (both in metres), and pour depth in millimetres, the tool instantly supplies:
- Ring surface area in square metres - functional for reinforcement or formwork estimates.
- Concrete volume in cubic metres - primary ordering quantity.
- Parallel figures in cubic yards and cubic feet for suppliers or crew working in imperial.
Using feet and inches? Switch to the Donut Concrete Calculator - Imperial.
More metric concrete tools:
Donut Shape Concrete Footing/Slab - Metric
Calculator
- enter the outer diameter in metres
- enter the inner diameter in metres
- the required depth in millimetres
Results
- width of footing or slab in metres
- square metres of this area (in case it is a slab)
- inside perimeter in metres
- outside perimeter, the circumference in metres
- combined perimeter the outside plus the inside added together
- concrete needed in cubic metres
- concrete needed in cubic yards
- amount of concrete needed in cubic feet
Formula's used:
Total AreaA = π * D² ÷ 4
where A is the area in square metres, π = 3.14159265358979, D = outer diameter of circle
Perimeter P = π * D ÷
where P is the perimeter in meters, π = 3.14159265358979, D = diameter of circle
Volume
V = π * D² ÷ 4 * d
where V is the volume in cubic metres, π = 3.14159265358979, D = diameter of circle, d = depth of slab in millimetres
Volume calculation example:
outer diameter = 20 metres inner diameter = 19 metres depth of slab = 100 millimetres 3.14159265358979 * 20 * 20 ÷ 4 ( 100 ÷ 1000) = 31.4 cubic metres 3.14159265358979 * 19 * 19 ÷ 4 ( 100 ÷ 1000) = 28.4 cubic metres 31.4 - 28.4 = 3 cubic metres of concrete needed for this footing
To convert cubic metres to cubic yards multiply cubic metres * 1.31
To convert cubic metres to cubic feet multiply cubic metres * 35.32
To convert cubic yards to cubic feet multiply cubic yards * 27