Last updated: 2026-02-12
Quick Answer
Use this concrete footing calculator to estimate cubic yards for continuous footings from width, depth, and total linear feet. It also shows an overage-adjusted total (waste %) plus approximate 60/80 lb bag counts for very small pours.
Inputs you’ll need
- Footing width (inches)
- Footing depth (inches)
- Total footing length (feet)
- Waste/overage % (optional, but recommended)
- Price per cubic yard + delivery/short-load fee (optional)
Related tools: Concrete Calculator, Concrete Cost Per Yard, and Rebar Weight Calculator.
How to use this footing calculator
- Enter footing width and depth from the plan (inches).
- Add total linear feet for all continuous footings (perimeter + interior).
- Set waste/overage (we default to 8%).
- Round your order per your batch plant minimums (many contractors round to the next 0.25 yd³).
If you want help turning takeoffs into a clean customer quote, start with our Construction Bid Template.
Preset sizes are common rules-of-thumb. Always follow engineered plans and local code.
Tip: use total linear feet for continuous footings (perimeter + interior runs).
Typical: 5–12% (forms not perfect, spillage, uneven trench).
Use your ready-mix quote (delivered price).
Optional flat fee (common on small pours).
Assumptions
- Volume is calculated as width × depth × length using your entered dimensions.
- Waste is applied as a simple percentage to the total volume.
- Bag counts use typical yields: 60 lb ≈ 0.45 ft³, 80 lb ≈ 0.60 ft³.
- Cost estimate includes optional price/yd + delivery fee; it does not include excavation, rebar, forming, or labor.
Concrete Footing Results
Total volume (yd³)
3.56
Total volume (ft³)
96.0
80-lb bags (approx)
160
60-lb bags (approx)
214
Detailed Breakdown
12,800+ estimates calculated this month
Note: For ready-mix ordering, many contractors round up to the next 0.25 yd³ (or follow your batch plant minimums).
Quick reference: volume per 10 linear feet
| Footing size | ft³ per 10 lf | yd³ per 10 lf |
|---|---|---|
| 16" × 8" | 8.89 | 0.329 |
| 18" × 10" | 12.50 | 0.463 |
| 24" × 12" | 20.00 | 0.741 |
Concrete Footing Guide
Standard footing sizes, rebar requirements, and soil bearing capacity for residential foundations.
Standard Concrete Footing Sizes by Structure
Residential footings are typically 12" deep × 16–24" wide, sized to spread structural loads across soil.
- Residential foundation wall: 12" deep × 16"–20" wide (minimum 2× wall thickness)
- Deck post footing: 12" deep × 16"–24" diameter (round Sonotube)
- Fence post footing: 8"–12" diameter × 24"–36" deep (below frost line)
- Garage/shop footing: 12" deep × 20"–24" wide
Frost line depth determines minimum footing depth: 12" in the South, 36"–48" in northern states, up to 60"+ in Alaska.
Key Takeaways
- Residential: 12" deep × 16"–20" wide minimum
- Footing width = 2× wall thickness (code minimum)
- Frost line: 12" (South) to 48"+ (North)
Footing Concrete Requirements & Rebar
Use 3,000–3,500 PSI concrete for residential footings with #4 rebar (1/2") as standard reinforcement.
- Continuous footings: 2 horizontal runs of #4 rebar, 3" from bottom, 3" from each edge
- Pier footings: 2 pieces #4 rebar crossed in a grid pattern at the base
- Vertical rebar (dowels): Extend 18"–24" above footing to tie into foundation wall
- Rebar cover: Minimum 3" of concrete on all sides (bottom: use chairs/supports)
A 100 linear foot foundation footing (12"×20") requires approximately 6.2 cubic yards of concrete.
Key Takeaways
- Use 3,000–3,500 PSI for residential footings
- #4 rebar (1/2") is standard for residential
- Minimum 3" concrete cover on all rebar
Soil Bearing Capacity & Footing Design
Soil bearing capacity determines footing width. Weak soils need wider footings to spread the load.
- Bedrock: 12,000+ PSF — minimal footing needed
- Gravel/sand-gravel: 3,000–5,000 PSF — standard footing widths
- Sand: 2,000–3,000 PSF — may need wider footings
- Clay: 1,500–2,500 PSF — often requires engineered footings
- Soft clay/silt: 1,000–1,500 PSF — may need piers or deep foundations
When in doubt, a geotechnical soil test ($500–$1,500) prevents costly foundation failures.
Key Takeaways
- Gravel soil: 3,000–5,000 PSF bearing capacity
- Clay soil may need engineered wider footings
- Soil test: $500–$1,500 (prevents costly failures)
Footing volume examples (5 test cases)
Use these to sanity-check your numbers. (Yards shown are before waste unless noted.)
| Case | Inputs | Expected |
|---|---|---|
| 1 | 16" × 8", length 100 ft, 0% waste | (16/12)×(8/12)×100 = 88.89 ft³ → 88.89/27 = 3.29 yd³ |
| 2 | 24" × 12", length 60 ft, 0% waste | (2.0)×(1.0)×60 = 120 ft³ → 120/27 = 4.44 yd³ |
| 3 | 18" × 10", length 120 ft, 0% waste | (1.5)×(0.8333)×120 = 150 ft³ → 150/27 = 5.56 yd³ |
| 4 | 12" × 12", length 40 ft, 0% waste | (1.0)×(1.0)×40 = 40 ft³ → 40/27 = 1.48 yd³ |
| 5 | 16" × 8", length 100 ft, 8% waste | Base 3.29 yd³ × 1.08 = 3.55 yd³ |
Common mistakes (avoid these)
- Using trench width instead of the planned footing width (or vice versa).
- Forgetting waste/overage and coming up short on pour day.
- Mixing inches and feet (width/depth are inches; length is feet).
- Ignoring batch plant minimums and short-load fees for small orders.
Pro tip: If you’re also taking off steel, run the same linear feet through the Rebar Weight Calculator.
Turn takeoffs into quotes (fast)
EstimationPro turns job photos, notes, and scope into clean estimates and proposal-ready line items. Try EstimationPro free.
How to Use This Calculator
Measure the footing size
Enter footing width and depth (inches). Use the engineered plan or your local code requirements.
Add total linear feet
Enter total length (ft) for all continuous footings (perimeter + interior runs).
Add waste/overage
Add 5–12% to cover uneven trenches, spillage, and small form changes. (Use your own standard.)
Optional: estimate cost
If you have a ready-mix quote, enter price per yard and any short-load/delivery fee.
Concrete Footing Formulas
Width (ft) = Width (in) ÷ 12
Depth (ft) = Depth (in) ÷ 12
Volume (ft³) = Width (ft) × Depth (ft) × Length (ft)
Volume (yd³) = Volume (ft³) ÷ 27
Volume w/ Waste = Volume × (1 + Waste%/100)
Estimated Concrete Cost = (Volume w/ Waste in yd³) × (Price per yd³) + Delivery FeeWhere:
- Waste%
- = Overage to cover uneven trenches, spillage, and small changes in the field
- Price per yd³
- = Optional delivered ready-mix price; set 0 to skip cost estimate
- Delivery Fee
- = Optional short-load or delivery fee
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Frequently Asked Questions
How do you calculate concrete for footings?
How many cubic yards are in a 16" × 8" footing per 100 feet?
How much waste should I add for footings?
Should I order concrete in bags or ready-mix for footings?
Does this footing calculator include rebar or labor?
Can I use this for stem walls or thickened-edge slabs?
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