Concrete Footing Calculator
Find the concrete for footings, column pads and piers. Measure in feet or metres, and see the sizes the building code (Part 9) asks for.
Measure your project
Your answer
That is 12.2 cubic feet, or 0.35 m³. We added 10% extra.
If you buy bags
Each 30 kg bag makes 0.014 m³, or 0.5 cubic foot.
If you order a truck (ready-mix)
Ask for 1.00 m³ (about 1.31 cubic yards). Ontario plant lists start at 1 m³, so we price at least that.
Footings hold up the building. Check your local building rules or ask a builder or engineer.
Which costs less?
But you must mix 25 bags by hand. That is 750 kg to lift.
Ready-mix (25 MPa): the middle of 4 lists from 3 companies in Ontario and Calgary. Footings need at least 15 MPa. Bags: the middle of 8 prices at 5 Ontario stores. October 2026, before GST/HST.
Quick answers
- Footing width, outside walls
- 250, 350 or 450 mm for 1, 2 or 3 storeys, says the building code (Part 9).
- How deep under a house
- In clay or unknown soil, at least 1.2 m (4 ft), says the building code (Part 9). With no heated space, also go below the frost line.
- 40 ft of footing, 10 × 4 in
- 0.45 cubic yards (0.35 m³) with 10% extra. Or 25 bags of 30 kg.
How to work it out
- Measure the footing length in feet. Measure the width and thickness in inches.
- Change the inches to feet: divide each by 12.
- Multiply length × width × thickness for the volume in cubic feet. Divide by 27 for cubic yards.
- Add 10% extra. Add any column pads and piers the same way.
250 mm → 10 in wide. 100 mm → 4 in thick
40 × 0.833 × 0.333 = 11.1 cubic feet
11.1 + 10% = 12.2 cubic feet
12.2 ÷ 27 = 0.45 cubic yards
Concrete footing sizes in the code (Part 9)
Column pads assume columns 3 m apart.
| Storeys | Outside walls | Inside walls | Column pad |
|---|---|---|---|
| 1 | 250 mm (9.8 in) | 200 mm (7.9 in) | 0.4 m² (4.3 sq ft) |
| 2 | 350 mm (13.8 in) | 350 mm (13.8 in) | 0.75 m² (8.1 sq ft) |
| 3 | 450 mm (17.7 in) | 500 mm (19.7 in) | 1 m² (10.8 sq ft) |
From Part 9 (BC Building Code 2018 and Ontario Building Code 2024 text).
- Brick on the outside: add 65 mm for each storey of brick facing. Add 130 mm for each storey of solid masonry walls.
- Wet ground: where the water table is high in gravel, sand or silt, make the footing 2 times as wide.
- Who it is for: the table is for houses on soil that holds at least 75 kPa. Joists must be up to 4.9 m long, and floor loads up to 2.4 kPa. Longer joists need a wider footing, worked out by a code formula. On weaker soil, an engineer must design the footing instead.
How thick: the sticking-out rule
A footing must be at least 100 mm thick, and as thick as it sticks out.
Example: 2 storeys with brick
Start at 350 mm. Add 65 mm for each of the 2 brick storeys: 480 mm wide.
Say it sits under a 150 mm concrete wall, the least in BC's 2024 code, in the middle. It sticks out 165 mm each side, so it must be at least 165 mm (6.5 in) thick. Your drawings set the real wall size.
How deep: frost and the 1.2 m rule
The code gives no frost depth for any city. It sets 1.2 m as the least depth in clay or unknown soil.
| Soil | Heated basement | No heated space |
|---|---|---|
| Rock | No limit | No limit |
| Coarse grained soils | No limit | No limit if it drains well; below frost depth if not |
| Silt | No limit | Below frost depth |
| Clay or soils not clearly defined | 1.2 m | 1.2 m, and below frost depth |
'No heated space' covers decks, unheated garages, piers and footings with insulation. Same Part 9 text as above.
Cities can ask for more
Winnipeg asks for 1.8 m (6 ft) under decks with joists more than 1,300 mm up. The rest of Manitoba asks 1.8 m (6 ft) once joists are more than 600 mm up.
For deck and pier depths in other cities, see the sonotube calculator. Check with your own city.
Low "floating" decks, up to 55 m² (about 592 sq ft), can skip frost footings. The questions below list every limit.
Concrete and steel for footings
Footings need at least 15 MPa concrete. Dufferin's 15 MPa footing mix is $254, on one Ontario list.
If you add bars, keep 75 mm of concrete between them and the soil, says Nanaimo's city spec. See the rebar calculator.
Dig down to soil nobody has moved, and pour on that. Footings hold up the house, so check your local building rules or ask a builder or engineer.
Questions people ask
How big should a concrete footing be?
Under an outside wall, 250 mm wide for 1 storey, 350 mm for 2 and 450 mm for 3. That is Canada's Part 9 table for houses on firm soil.
How thick should a concrete footing be?
At least 100 mm. It must also be at least as thick as it sticks out past the wall or column.
How deep does a concrete footer or footing need to be?
In Canada, it depends on the soil and on heat. In clay or unknown soil, the building code (Part 9) asks for at least 1.2 m. With no heated space, go below the frost line too. Winnipeg and Manitoba ask 1.8 m for decks.
What strength of concrete do footings need?
At least 15 MPa, says the building code (Part 9).
Do footings need rebar in Canada?
Part 9 has no rebar rule for house footings. It covers plain or lightly reinforced concrete. Footings designed as reinforced concrete need an engineer (Part 4).
Does a deck need footings below the frost line?
Not a low "floating" deck. That means 1 storey, up to 55 m², with joists no more than 600 mm up. It must have no roof and not be attached. Other decks follow the depth rules and your city.
How big should a column pad be?
The building code (Part 9) asks for 0.4 m² for 1 storey, with columns 3 m apart. That is about 632 mm square.
Where our numbers come from
- Footings and piers: BC Building Code 2018, Section 9.15
- Footing sizes: Ontario Building Code Table 9.15.3.4 (2012 text, third-party copy)
- Ontario Building Code 2024, Part 9 (ministry compendium)
- Foundation depth: BC Building Code 2018, Section 9.12 (Table 9.12.2.2)
- What changed in 2024: BOABC list of BC Building Code revisions (footings and foundations)
- Concrete strength and site mixes: BC Building Code 2018, Section 9.3 (Part 9)
- Deck footing depth: City of Calgary deck permit checklist (1.2 m)
- Deck footing depth: City of Winnipeg decks brochure (1.8 m)
- Deck footing depth: Manitoba building code guide 06 (1.8 m)
- Rebar cover: City of Nanaimo engineering standards, Section 11
- Small-load and winter fees: Dufferin Concrete 2026 price list (Ontario)
- Ready-mix price: the middle of 4 prices from 3 companies (25 MPa, Oct 2026, before tax)
- Small-load fees: CBM Toronto-area price list
- Bag size: Sakrete Canada Concrete Mix (30 kg makes 0.014 m³, or ½ cubic foot)
- Store prices: Ontario Home Depot, RONA, Home Hardware and Chamberlain Timber Mart (Oct 2026)
- Extra for spills: Sakrete slab calculator (10%)
Made by BuildersCount. Last checked 4 Oct 2026.
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