Footing Calculator

Isolated footings spread a column’s load into the ground. Each usually sits on a thin bed of plain cement concrete (PCC). This calculator gives the concrete for all footings and the PCC bed.

Measure in
Results update as you type.

Cement

22 bags

21.92 bags of 50 kg for 2.72 m³ of M20

Footing concrete
2.72 m³ (96 cft)
Sand
1.14 m³ (40.3 cft)0.4 brass
Aggregate (gitti)
2.28 m³ (80.6 cft)0.81 brass
Water (approx.)
548 litreswater–cement ratio 0.5
PCC bed (M7.5, 75 mm wider each way)
0.86 m³ (30.3 cft)2.9 more bags of cement

Nominal mixes are for estimating. Structural concrete should follow the engineer’s design mix. Add 3% to 5% for wastage.

About this calculator

Enter one footing’s size and depth and the number of footings.

How to use it

  1. Choose feet or metres and enter the dimensions.
  2. Choose the mix or materials.
  3. Read the quantities to order.

The formula

Footing volume = length × width × depth × number
PCC bed
M7.5, 75 mm wider on each side

Worked example

Six footings of 4 × 4 ft, 12 in deep, on a 3 in PCC bed

  1. Footing concrete = 1.22 × 1.22 × 0.305 × 6 = 2.72 m³ (96 cft).
  2. M20 needs about 22 bags of cement.
  3. The PCC bed adds 0.86 m³.

What the result means

Stepped or sloped footings need their parts calculated separately.

Assumptions

  • Rectangular footings with flat tops.

Limitations

  • Footing size and reinforcement must come from a structural design.

Frequently asked questions

What thickness is PCC under a footing?

Commonly 75 to 150 mm.

Which grade for footings?

M20 or as the engineer specifies.

Is excavation included?

No; use the soil calculator for digging.

Last reviewed on 3 October 2026. Found a mistake? Tell us.