About this calculator
Estimate concrete for continuous (strip) footings under walls. Enter the total length of all runs, then the width and depth.
How it’s calculated
Volume = total length × width × depth, plus waste. For a rectangular building, the total length is roughly the perimeter. Measure along the centreline of the footing so the corners aren’t counted twice.
Worked example
With these inputs:
- Total footing length
- 60 ft
- Width
- 16 in
- Depth
- 8 in
- Supply as
- Pre-mixed bags
- Bag size
- 30 kg
- Waste allowance
- 10%
the result is:
- Concrete needed
- 1.66 m³
- Net volume
- 1.51 m³
- Plan area
- 80 sq ft
- Ready-mix order (to 0.25 m³)
- 1.75 m³ (2.29 cu yd)
- 30 kg bag
- 119 bags
Tips from the trade
- Dug trenches are rarely neat. Allow 10–15% waste, or more in sandy soil where the sides slump.
- Footing size depends on the load and the soil. Part 9 of your provincial building code gives minimum footing sizes for houses, and footings must sit below frost depth, often 4 ft (1.2 m). Follow your plans.
- Order ready-mix with a little spare. Running short on a footing pour leaves a cold joint.
Common questions
How do I measure a footing perimeter?
Add the centreline lengths of every wall run. For a simple rectangle, that is 2 × (length + width) minus 4 × the footing width.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the building code adopted in your province before ordering.