Enter your footing dimensions and instantly calculate concrete volume in cubic yards, bag counts, and total cost estimate. Supports strip footings, pad footings, and spread footings.
Free to use
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Formulas verified against ACI 318
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Imperial & metric supported
✓ Strip, pad & spread footings✓ Multiple footing count✓ Cost estimator included✓ Last verified May 2026
Strip footing: a long, continuous rectangular footing under a wall or foundation wall.
Total run of the footing. For strip footings, measure the full perimeter or linear run.Please enter a valid length greater than 0.
Footing width. IRC minimum is 12 in for most residential walls; typical is 16–24 in.Please enter a valid width greater than 0.
Thickness of the footing itself, not the depth of excavation. Typical: 8–12 in residential.Please enter a valid depth greater than 0.
For pad/pier footings, enter the total number of identical footings. Use 1 for a continuous strip.
Add 5–10% for standard pours. Uneven trench bottoms can consume more concrete than expected — 10% is a safe minimum.
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Leave blank to skip cost estimate. US average: $110–$160/yd³ for ready-mix delivered to site.
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Your Footing Estimate
Concrete Volume (with waste)
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Cubic Yards (yd³)
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Cubic Feet (ft³)
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Cubic Meters (m³)
Bags Required (includes waste)
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40 lb bags
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60 lb bags
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80 lb bags
—Per Footing (yd³)
—Footings
—Depth
—Waste Factor
Estimated Material Cost
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Concrete material cost only. Add excavation ($3–$8/linear ft), forming lumber, labor ($4–$8/lin ft), and rebar for a full budget. Use our Full Project Estimator for a complete breakdown.
Step 1: Convert all dimensions to feet
Step 2: Single footing volume (ft³) = Length (ft) × Width (ft) × Depth (ft)
Step 3: Total volume (ft³) = Single volume × Number of footings
Step 4: Cubic Yards = Total ft³ ÷ 27
Step 5: Final Volume = Volume × (1 + waste% ÷ 100)
Step 6: Bags = CEIL(Final ft³ ÷ bag yield) — never round down
Select your footing type and measure the dimensions.
Choose Strip/Continuous if you're pouring a wall footing that runs the full perimeter of a building — enter the total linear run of the footing, not just one wall. Choose Pad/Spread for isolated column footings — enter a single footing's dimensions and the total footing count. Measure length and width inside the form boards, not the outside of the lumber.
Enter width and depth with the correct units.
Footing width and depth are almost always in inches on a residential project — use the inch dropdown. A common mistake is entering 16 feet instead of 16 inches for a footing width. Double-check your units before calculating.
Set the footing count and waste factor.
For pad footings supporting a deck or post frame building, enter the exact number of pads. Leave at 1 for a continuous strip. Set waste to 10% for most pours — trench bottoms are never perfectly flat, and any concrete that drops into loose soil below the bearing surface is wasted volume.
Use the cubic yards figure when ordering ready-mix.
Give this number to the ready-mix dispatcher. For anything under 1 yard, bag concrete is more economical. For jobs between 1–2 yards, get quotes from both the batch plant and your hardware store — the minimum delivery charge for a short load can make bags competitive at small volumes.
⚠ Pro Tip: The most expensive footing mistake isn't the concrete — it's the bottom of the trench. If the excavator over-digs or rain softens the bearing surface, you pour extra concrete to fill the low spots. Always clean and compact the trench bottom, and add 5–10% waste beyond what the calculator shows for trenched strip footings.
Concrete Footing Volume Formula
Footing concrete volume uses the standard rectangular volume formula. The key is ensuring all dimensions are in consistent units before calculating. Here's the step-by-step process:
Step
Formula
Example (20 ft × 16 in × 12 in, 1 footing)
1. Convert width to feet
inches ÷ 12
16 ÷ 12 = 1.333 ft
2. Convert depth to feet
inches ÷ 12
12 ÷ 12 = 1.000 ft
3. Volume in cubic feet
L × W × D
20 × 1.333 × 1.000 = 26.67 ft³
4. Convert to cubic yards
ft³ ÷ 27
26.67 ÷ 27 = 0.988 yd³
5. Add waste factor (10%)
Volume × 1.10
0.988 × 1.10 = 1.086 yd³
Common Footing Size Reference Table
Concrete volumes for common footing configurations — no waste factor applied. Add 10% for real-world ordering.
Footing Length
Width × Depth
Cubic Feet
Cubic Yards
60 lb Bags
20 linear ft
12 in × 8 in
13.33 ft³
0.49 yd³
30 bags
20 linear ft
16 in × 12 in
26.67 ft³
0.99 yd³
60 bags
40 linear ft
16 in × 12 in
53.33 ft³
1.98 yd³
119 bags
60 linear ft
16 in × 12 in
80.00 ft³
2.96 yd³
178 bags
100 linear ft
20 in × 12 in
166.67 ft³
6.17 yd³
371 bags
120 linear ft
24 in × 16 in
384.00 ft³
14.22 yd³
854 bags
8 pad footings
24 in × 24 in × 12 in each
32.00 ft³
1.19 yd³
72 bags
12 pad footings
30 in × 30 in × 12 in each
75.00 ft³
2.78 yd³
167 bags
Bag counts assume no waste factor and use 0.45 ft³ yield per 60 lb bag. Add 10% for real-world ordering.
What Depth Does My Concrete Footing Need?
Footing depth is not optional — it's governed by local frost depth and the bearing capacity of the soil beneath. Going too shallow is the single most common footing failure mode in cold climates. The footing must bear on undisturbed soil below the frost line.
Recommended minimum footing depths by application and climate zone.
Application
Footing Depth (to bottom)
Footing Thickness
Notes
Southern US / warm climates (frost depth <6 in)
12 in minimum
8–12 in
Must bear on undisturbed native soil
Mid-Atlantic / moderate climates (frost 12–24 in)
24–30 in
10–12 in
Check local codes; often 18 in minimum
Northern US / Midwest (frost 36–48 in)
42–54 in
12 in
Below local frost depth is non-negotiable
Canada / upper Midwest (frost 48–72 in)
54–78 in
12–16 in
Often 60 in+ by code; verify with authority
Deck post footings (freestanding)
Below local frost line
Pad or tube, 8–16 in dia.
Many jurisdictions allow frost-protected shallow
Interior column footings (heated slab)
Below slab, on compacted gravel
12–16 in
No frost concern; soil bearing governs
Retaining wall footings
Below frost line, minimum 24 in
12–16 in (≥ wall thickness)
Lateral load — engineer review recommended
Never assume the frost depth. Look up your jurisdiction's required footing depth on the IRC frost depth map or call your local building department — it's a 2-minute phone call that can save you from a failed inspection or a frost-heaved footing next spring.
Common Mistakes When Estimating Footing Concrete
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Confusing footing depth with excavation depth.
The footing depth (what you enter in this calculator) is the thickness of the concrete footing itself — typically 8 to 16 inches. The excavation depth is how far down you dig, which includes the footing plus any gravel drainage bed below it. Entering total excavation depth into a footing calculator will dramatically over-order concrete.
📐
Entering footing width in feet instead of inches.
The most common unit error in footing calculations. A 16-inch-wide footing entered as "16 feet" produces a number 12 times too large. Always confirm your units before calculating — the calculator defaults width and depth to inches because that's how footings are specified on virtually every US residential drawing.
🔢
Not counting all footing runs separately.
A house foundation has a perimeter footing plus interior load-bearing wall footings. If you only calculate the perimeter, you'll miss the interior runs. Add all linear footage of footing — exterior and interior — and run a single calculation with the total length.
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Ignoring the trench bottom condition.
Concrete poured into a wet, muddy, or loosely backfilled trench will lose volume to absorption and voids. Always pour on undisturbed or well-compacted soil. If the trench bottom is soft, install a thin gravel bed and compact it before pouring. Factor an additional 5–10% overage for any trench that isn't clean and firm.
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Assuming bagged concrete is economical for large footings.
Bagged concrete at $6–$8 per 80-lb bag (0.60 ft³) costs roughly $270–$360 per cubic yard. Ready-mix delivered to site averages $110–$160 per cubic yard. For anything over 1.5 cubic yards, a ready-mix delivery is almost always cheaper — even after the short-load fee. Run the math before buying bags for a whole-house foundation.
Frequently Asked Questions
Multiply the footing length by its width by its depth — all in feet — to get cubic feet of concrete. Divide by 27 to convert to cubic yards. Then multiply by 1.10 to add a 10% waste factor. For multiple identical footings, multiply a single footing's volume by the count before adding waste. This calculator does all of that automatically once you enter your dimensions.
A strip footing (also called a continuous footing) is a long rectangular beam of concrete that runs under a wall continuously, distributing the wall's load across the soil. It's used for foundation walls and load-bearing walls. A pad footing (or spread footing) is a discrete square or rectangular block of concrete placed under a single point load — most commonly a column, post, or pier. Decks, pole barns, and post-frame buildings use pad footings at each post location. Both use the same volume formula; they just differ in count and plan shape.
The minimum footing width under the IRC is typically 12 inches for residential construction, but the practical standard is to make the footing at least twice as wide as the wall it supports. For an 8-inch foundation wall, the footing is typically 16 inches wide. For a 10-inch wall, 20 inches. For load-bearing situations on soft soils, an engineer may specify a wider footing to reduce bearing pressure. Footing width is governed by soil bearing capacity, wall loads, and local code — always verify with your building department or structural engineer for anything other than a basic residential project.
The bottom of the footing — not the top — must be below the local frost depth. Frost depths vary widely: as shallow as 6 inches in coastal California and as deep as 72 inches or more in northern Minnesota or Canada. Check the IRC frost depth map for your county or call your local building department for the required minimum footing depth. A footing that sits above the frost line will heave every winter as the soil freezes and expands, cracking the foundation above it. This is non-negotiable in any climate that experiences ground freezing.
Most residential footings use 3,000 PSI concrete (standard mix). In freeze-thaw climates or where the footing may be exposed to de-icing salts, specify 4,000 PSI with air entrainment. For footings exposed to sulfate-bearing soils, use sulfate-resistant cement (Type V or Type II) per ACI 318 recommendations. Higher-strength concrete (3,500–4,000 PSI) is often specified for commercial footings and any footing with a design load calculated by a structural engineer. Never use less than 2,500 PSI for a footing, even on small projects.
Most residential strip footings require a minimum of two continuous #4 rebar (1/2-inch diameter) running horizontally the full length of the footing, placed near the bottom with 3 inches of concrete cover. Many codes also require vertical dowels (#4 at 4-foot spacing or per engineer) projecting up into the foundation wall above. Pad footings typically require a grid of rebar at 12-inch spacing in both directions. Always check your local building code — unreinforced footings are allowed in some low-seismic, non-expansive-soil jurisdictions, but reinforcement is best practice in virtually every case.
For jobs under about 1 cubic yard (27 cubic feet), bagged concrete is practical — you can mix and pour at your own pace. Above 1 cubic yard, ready-mix becomes competitive on price and far more practical on a jobsite. A whole-house foundation footing typically requires 3–15+ cubic yards; using bags for that volume means hundreds of 80-lb bags mixed by hand or in a rented drum mixer, with a real risk of cold joints if the pour takes too long. Ready-mix plants can add short-load surcharges for orders under 5 yards — factor that into your cost comparison.
Concrete can be successfully placed in cold weather, but it requires precautions. ACI 306 defines cold weather concreting as any time the air temperature drops below 40°F (4°C) for three or more consecutive days. At these temperatures, the hydration reaction slows dramatically and fresh concrete can freeze before it reaches sufficient strength. Practical cold-weather footing measures include using hot water in the mix (your ready-mix plant can do this), placing insulated blankets or heated enclosures over the footing immediately after pouring, and ensuring the subgrade is not frozen before placing concrete. Never pour on frozen ground — the footing will settle when the soil thaws.
Industry standard is to allow footing concrete to cure for a minimum of 3 to 7 days before placing significant loads on it — such as pouring a foundation wall or setting framing. At 7 days, concrete has typically reached about 70% of its 28-day design strength, which is sufficient for most construction loading. Do not strike forms or backfill against a foundation wall until the footing below has reached adequate strength. In cold weather, extend the waiting period — concrete gains strength much more slowly below 50°F.
Yes, in virtually all US jurisdictions, footings for any structure that requires a building permit also require a footing inspection before concrete is placed. The inspector checks that the trench is at the correct depth (below frost line), the width and dimensions are per the approved drawings, the rebar is correctly placed and tied, and the bearing surface is clean and undisturbed. Do not pour concrete until the inspection has been passed and documented. Pouring without inspection can result in a stop-work order, required demolition, and fines. Even small structures like sheds or decks over a certain size typically require footing permits.
