Concrete Footing Size Chart

How big a concrete footing needs to be: square footings for column and post loads of 10 to 150 kips, and wall footing widths, on soils that allow 1,500 to 4,000 pounds per square foot.

Each column footing is the smallest that keeps the soil pressure under the allowable value, and is thick enough and reinforced enough to pass the ACI 318-19 checks for one-way shear, two-way (punching) shear, bending and bar development, the same checks as the free footing designer.

Allowable soil bearing pressure

The soil sets the footing's area. Without a soil report, the International Residential Code (IRC) lets you use these presumptive values (Table R401.4.1); the building department may require a report where the soil is in doubt.

Soil	Allowable bearing pressure
Crystalline bedrock	12,000 psf
Sedimentary and foliated rock	4,000 psf
Sandy gravel and gravel	3,000 psf
Sand, silty sand, clayey sand, silty gravel and clayey gravel	2,000 psf
Clay, sandy clay, silty clay, clayey silt, silt and sandy silt	1,500 psf

Column footing size chart

Footing width × thickness, and the bottom bars each way, for a square footing under a 12 in square column or pier. Loads are service (unfactored) loads on the footing in kips (1 kip = 1,000 lb).

Square column footings: width × thickness and bars
Column load	1,500 psf	2,000 psf	2,500 psf	3,000 psf	4,000 psf
10 kips	2′‑9″ × 12″ 4 #4^h each way	2′‑6″ × 12″ 4 #4^h each way	2′‑6″ × 12″ 4 #4^h each way	2′‑6″ × 12″ 4 #4^h each way	2′‑6″ × 12″ 4 #4^h each way
15 kips	3′‑6″ × 12″ 5 #4 each way	3′‑0″ × 12″ 4 #4^h each way	2′‑9″ × 12″ 4 #4^h each way	2′‑6″ × 12″ 4 #4^h each way	2′‑6″ × 12″ 4 #4^h each way
20 kips	4′‑0″ × 12″ 6 #4 each way	3′‑6″ × 12″ 5 #4 each way	3′‑0″ × 12″ 4 #4^h each way	2′‑9″ × 12″ 4 #4^h each way	2′‑6″ × 12″ 4 #4^h each way
25 kips	4′‑6″ × 12″ 6 #4 each way	3′‑9″ × 12″ 5 #4 each way	3′‑6″ × 12″ 5 #4 each way	3′‑0″ × 12″ 4 #4^h each way	2′‑9″ × 12″ 4 #4^h each way
30 kips	4′‑9″ × 12″ 7 #4 each way	4′‑3″ × 12″ 6 #4 each way	3′‑9″ × 12″ 5 #4 each way	3′‑3″ × 12″ 5 #4^h each way	3′‑0″ × 12″ 4 #4^h each way
40 kips	5′‑6″ × 12″ 8 #4 each way	4′‑9″ × 12″ 7 #4 each way	4′‑3″ × 12″ 6 #4 each way	3′‑9″ × 12″ 5 #4 each way	3′‑3″ × 12″ 5 #4^h each way
50 kips	6′‑3″ × 12″ 9 #4 each way	5′‑3″ × 12″ 7 #4 each way	4′‑9″ × 12″ 7 #4 each way	4′‑3″ × 12″ 6 #4 each way	3′‑9″ × 12″ 5 #4 each way
60 kips	6′‑9″ × 12″ 9 #4 each way	5′‑9″ × 12″ 8 #4 each way	5′‑3″ × 12″ 7 #4 each way	4′‑9″ × 12″ 7 #4 each way	4′‑0″ × 12″ 6 #4 each way
80 kips	8′‑0″ × 14″ 8 #5 each way	6′‑9″ × 12″ 10 #4 each way	6′‑0″ × 12″ 9 #4 each way	5′‑6″ × 12″ 8 #4 each way	4′‑9″ × 12″ 7 #4 each way
100 kips	8′‑9″ × 14″ 10 #5 each way	7′‑6″ × 14″ 8 #5 each way	6′‑9″ × 14″ 7 #5 each way	6′‑0″ × 14″ 6 #5 each way	5′‑3″ × 14″ 8 #4 each way
125 kips	10′‑0″ × 16″ 12 #5 each way	8′‑6″ × 16″ 10 #5 each way	7′‑6″ × 16″ 9 #5 each way	6′‑9″ × 16″ 8 #5 each way	5′‑9″ × 16″ 7 #5 each way
150 kips	11′‑0″ × 18″ 14 #5 each way	9′‑3″ × 18″ 12 #5 each way	8′‑3″ × 18″ 11 #5 each way	7′‑6″ × 18″ 10 #5 each way	6′‑6″ × 18″ 9 #5 each way

3000 psi concrete, grade 60 bars with 3 in of cover, and 70% of the load taken as live load. The footing's own weight (150 lb/ft³) is taken off the allowable soil pressure; soil or a slab on top of the footing isn't.
Widths are rounded up to 3 in, with 2 ft 6 in the smallest. Thicknesses start at 12 in.
^h These bars need standard 90° hooks at their ends, because the footing is too small to develop them straight.
The column is centered on the footing and carries no moment or uplift.

For example, a post holding up a 12 ft × 14 ft area of two floors at 55 psf (15 dead and 40 live) carries 168 × 2 × 55 = 18,480 lb, or 18.5 kips. On 2,000 psf soil, use the 20 kip row: a 3′‑6″ square footing 12 in thick with 5 #4 bars each way.

Wall footing width chart

The width of a continuous footing under a wall, in inches, for the load per foot of wall. The footing is taken as 8 in thick.

Wall footing width, inches
Wall load	1,500 psf	2,000 psf	2,500 psf	3,000 psf	4,000 psf
1,000 lb/ft	12 in	12 in	12 in	12 in	12 in
1,500 lb/ft	14 in	12 in	12 in	12 in	12 in
2,000 lb/ft	18 in	14 in	12 in	12 in	12 in
2,500 lb/ft	22 in	16 in	14 in	12 in	12 in
3,000 lb/ft	26 in	20 in	16 in	14 in	12 in
4,000 lb/ft	36 in	26 in	20 in	18 in	14 in
5,000 lb/ft	44 in	32 in	26 in	22 in	16 in
6,000 lb/ft	52 in	38 in	30 in	26 in	20 in

The IRC sets the minimums for house footings: at least 12 in wide and 6 in thick, with the footing projecting at least 2 in past each face of the wall but no more than the footing is thick (section R403.1.1). Wider footings than that need more thickness or reinforcement.

Concrete footing questions

How big should a footing be?

Big enough that the load divided by its area is under the soil's allowable bearing pressure. A 20 kip (20,000 lb) post load on 2,000 psf soil needs about 10 ft², so a footing a little over 3 ft square; the chart gives 3′‑6″ once the footing's own weight is included.

How thick should a footing be?

Thick enough that the column doesn't punch through it. Small footings are set by the 12 in minimum used here; footings for larger loads get thicker, 18 in for 150 kips on soft soil. ACI 318 requires at least 6 in of concrete above the bottom bars.

How deep should a footing be?

Below the frost line, which the local building department sets, and on undisturbed soil. In frost-free areas the IRC requires at least 12 in below the undisturbed ground surface.

Does a footing need rebar?

Footings for columns and posts with real loads do; the chart gives the bars. Small house footings are often plain concrete under the IRC, which is fine within its limits.

For other loads, column sizes, soil and concrete, use the free footing designer or follow the concrete footing design guide.