Concrete Footing for 100 Linear Feet
This calculator is pre-filled to estimate the concrete for 100 linear feet of footing. Change any field to match your project, and enter your local price for a precise cost.
Quick answer: 100 linear feet of footing at 1.5 ft wide and 12 in deep needs about 5.83 cubic yards of concrete (158 cu ft) — roughly 263 80 lb bags.
Concrete Footing calculator
How it's calculated: Total run length ft × footing width ft × (depth in ÷ 12) = cubic feet; add 5% waste and divide by 27 for cubic yards. An 80 lb bag yields about 0.6 cu ft.
How to estimate concrete footing
- Footing size is set by your local code and soil; common residential footings run 16-24 inches wide and 8-12 inches deep.
- Add the length of every footing run together for total length, including corners.
- Pour footings monolithically where possible so you are not joining cold pours.
- Call 811 for utility locates before trenching - footing depth is exactly where service lines live.
- If the job needs a permit, schedule the footing inspection while the trench is open; inspectors want to see soil and rebar before concrete.
Frequently asked questions
What do I need for 100 linear feet of footing?
100 linear feet of footing at 1.5 ft wide and 12 in deep needs about 5.83 cubic yards of concrete (158 cu ft) — roughly 263 80 lb bags.
How deep should a footing be?
Footings must sit below the local frost line and on undisturbed soil. Depth is code-driven, commonly 12 inches or more in cold climates.
How much concrete per linear foot of footing?
Multiply width by depth in feet. A 16x8 inch footing is about 0.9 cu ft per linear foot (roughly 30 ft of run per cubic yard); a wide 24x12 inch footing is 2 cu ft per foot, or about 13 ft per yard.
Should I use bags or ready-mix for footings?
An 80 lb bag yields about 0.6 cu ft, so even a modest 40 ft footing run can take 100+ bags. Hand-mixing that many risks weak, inconsistent concrete - order ready-mix for anything near a cubic yard.
Do footings need rebar?
Most codes call for continuous horizontal bars in footings - commonly two runs - with sizes set locally. Get the rebar requirement from your building department before the pour, not after.
Can I pour a footing in sections?
Avoid it where you can; a cold joint is a weak point. If a break is unavoidable, stop the pour at an approved keyway or leave rebar dowels sticking out to tie the next section in.