Concrete Footing Calculator
Enter your footing size to get the concrete you need in cubic yards, metres cubed and bags, plus an estimated cost. Waste is included.
Concrete needed
Estimated cost
How to calculate concrete for a footing
A footing is a long, narrow slab, so the math is the same as a slab. Multiply length by width by depth, with everything in feet, then convert to cubic yards by dividing by 27. Depth is usually quoted in inches, so divide it by 12 first.
Formula: cubic yards = length (ft) × width (ft) × depth (in ÷ 12) × (1 + waste %) ÷ 27
Worked example: 30 ft × 2 ft × 12 in footing
Volume = 30 × 2 × (12 ÷ 12) = 60 ft³. Add 10% for waste and uneven ground: 66 ft³. Divide by 27: 2.44 cubic yards. In bags, that is 110 bags of 80 lb mix.
How wide and deep should a footing be?
Footings are normally 12 inches deep and at least twice as wide as the wall they carry. Wide, shallow footings spread the load, but the exact size depends on soil and load, so check your local building code.
Ready-mix or bags?
As a rule of thumb, bags make sense under about 1 cubic yard. Above that, mixing by hand is slow and the cost per yard of bagged concrete is usually higher than ready-mix. Ready-mix suppliers often add a short-load fee for small orders, so check your local minimum before you compare prices.
Common footing sizes
Cost tips
Prices on this page are editable estimates, not quotes. Get 2 to 3 local quotes before you buy, and ask if delivery is included. Delivery, tax and waste can change the total a lot. Order a little extra for cuts and breakage, and confirm final quantities with your supplier or a qualified professional.
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Frequently asked questions
How much concrete do I need for a footing?
A 30 ft by 2 ft footing at 12 inches deep needs about 2.44 cubic yards with 10% waste, which is roughly 110 bags of 80 lb mix.
How wide and deep should a footing be?
Footings are usually 12 inches deep and at least twice as wide as the wall they carry. Follow your local building code.
Do concrete footings need rebar?
Most footings need steel reinforcement. Check your local code or ask an engineer for your project.
How much waste should I add?
Add 5 to 10 percent. Use 10 percent or more on uneven ground, and when you are pouring into an excavated trench.
Are the prices accurate?
Prices are editable estimates. The defaults are typical US figures, and your local price can be higher or lower. Delivery and short-load fees are not included.
How many bags are in a cubic yard?
One cubic yard is about 45 bags of 80 lb mix, or 60 bags of 60 lb mix.