Spike's Calculators

Calculate the amount of concrete needed in cubic metres and cubic yards for a donut shaped footing or slab.

Note: this is a circular area with a circular hole on the inside, not a torus!!

To be able to calculate the concrete volume needed for this type of footing you need to know the outer diameter of the circle, the inner diameter and the required depth.

A = π * D² ÷ 4

where A is the area in square metres, π = 3.14159265358979, D = outer diameter of circle

where P is the perimeter in meters, π = 3.14159265358979, D = diameter of circle

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

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

- enter the outer diameter in metres
- enter the inner diameter in metres
- the required depth in millimetres

- 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

- Circle
- Circle - Metric
- Donut
- Donut - Metric
- Ellipse
- Ellipse - Metric
- Equilateral Triangle
- Equilateral Triangle - Metric
- Octagon
- Octagon - Metric
- Oval
- Pentagon
- Pentagon - Metric
- Scalene Triangle
- Scalene Triangle - Metric
- Stadium Shape
- Stadium Shape - Metric
- Trapazoid
- Trapezium
- Plastic Concrete Footing Form