Last updated: 2026-03-06
Quick Answer
To calculate concrete for footings: Volume (ft³) = Width (ft) × Depth (ft) × Length (ft), then divide by 27 to get cubic yards. Add 5–12% for waste. This footing calculator handles the math instantly - enter your footing dimensions in inches and total linear feet, and it returns cubic yards, 60/80 lb bag counts, and an optional ready-mix cost estimate.
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 |
Standard IRC footing sizes by application
These are IRC minimums for typical residential construction. Local codes may require larger footings depending on soil type, load, and frost depth.
| Application | Width | Depth | Notes |
|---|---|---|---|
| Single-story wood frame | 12"–16" | 6"–8" | Most common residential minimum |
| Two-story wood frame | 18"–24" | 8"–12" | Wider to distribute increased load |
| Detached garage / shed | 12" | 6"–8" | Some jurisdictions allow 10" wide |
| Deck (standard post) | 16"–24" dia. | Below frost | Typically round tube forms; use Concrete Calculator |
| Retaining wall (residential) | 2× wall height | 12"–18" | Width depends on soil pressure and wall height |
Source: IRC Table R403.1. Always verify with your local building department.
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)
Once you have your material quantities, EstimationPro turns them into a professional proposal in minutes - then automatically follows up with the homeowner so you win more of the bids you already send. No more losing jobs because a competitor replied first. 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
Free to Embed on Your Website
Add this calculator to your blog, resource page, or client portal — just copy one line of code. Your visitors get a useful tool, you get more engagement.
EstimationPro AI For Contractors, By Contractors From Material Quantities to Full Project Estimates
You have the numbers. Now generate a professional estimate with materials, labor, and markup included.
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?
What are standard footing sizes for residential construction?
How deep do footings need to be below grade?
Related Articles
Why Contractors Choose EstimationPro AI
Estimates in 60 Seconds
AI generates detailed, line-item estimates from basic project details. No more hours on spreadsheets.
Accurate Pricing Data
Built on real contractor pricing and industry cost databases, updated for 2026 market conditions.
Professional Proposals
Send polished PDF estimates with your branding. Clients see a professional contractor they can trust.
Get Paid Faster
Built-in invoicing and Stripe payments. Collect deposits and progress payments directly from estimates.
Related Free Tools
Drywall Calculator
Calculate drywall sheets, joint compound, tape, and screws needed for any room. Enter dimensions to get a complete materials list.
Fence Calculator
Calculate fence materials and costs. Enter linear feet and fence type to get posts, rails, pickets, concrete, and total cost estimates.
Concrete Calculator
Calculate cubic yards of concrete needed for slabs, footings, columns, and walls. Enter dimensions to get volume, bags, and cost estimates.
Roofing Calculator
Calculate roofing materials and costs. Enter roof dimensions and pitch to get shingles, underlayment, flashing, and total project cost.
Paint Calculator
Calculate how much paint you need for any room or surface. Enter dimensions and get gallons needed, with cost estimates for different paint grades.
Mulch Calculator
Calculate cubic yards and bags of mulch needed for your landscaping project. Enter bed dimensions and desired depth for accurate quantities.
Gravel Calculator
Calculate tons and cubic yards of gravel needed for driveways, paths, and landscaping. Enter area dimensions and depth for accurate estimates.
Sand Calculator
Calculate tons and cubic yards of sand needed for bedding, fill, masonry, and concrete projects. Enter area dimensions and depth for accurate estimates.