Concrete Footing Calculator: Calculate Footing Concrete Volume
Use this concrete footing calculator to find the volume of concrete needed for strip footings, deck footings, or column pads, plus how many bags that works out to if you're mixing by hand. It's built for contractors and DIY builders planning a foundation pour. Enter your footing dimensions and how many you're pouring, and it returns volume per footing, total volume, and bag counts for both 60 lb and 80 lb mix.
How to use this calculator.
- Enter footing length. Measure the run of a single footing in feet.
- Enter footing width and depth. Both are entered in inches: check your local building code for the minimum sizing your soil and frost line require.
- Enter the number of footings. Count identical footings (e.g., 4 deck post footings) so the calculator can total them.
- Review your results. The calculator shows volume per footing, total volume in cubic yards, and bag counts if you're buying pre-mixed bags instead of ready-mix.
- Decide bagged vs. ready-mix. Under roughly 1 cubic yard, bagged mix is usually cheaper; above that, a ready-mix delivery is typically more cost-effective.
How do you calculate concrete footing volume?
The calculator finds the volume of one footing, multiplies by how many you're pouring, and converts to cubic yards and bag counts.
Volume per Footing (cu ft) = Length × (Width ÷ 12) × (Depth ÷ 12)
Total Volume (cu yd) = (Volume per Footing × Quantity) ÷ 27
60 lb Bags = (Total Volume × 27) ÷ 0.45 | 80 lb Bags = (Total Volume × 27) ÷ 0.6
Where:
- Length: Footing run, in feet. Widthand Depth: footing cross-section, in inches (divided by 12 to convert to feet).
- Quantity: Number of identical footings being poured.
- 0.45 / 0.6: Cubic feet of concrete yielded by one 60 lb or 80 lb bag of pre-mixed concrete, respectively.
Example calculation.
Scenario: You're pouring 4 identical footings for a deck, each 30 ft long, 16 inches wide, and 12 inches deep.
- Convert width and depth to feet: 16 ÷ 12 = 1.33 ft; 12 ÷ 12 = 1 ft
- Calculate volume per footing: 30 ft × 1.33 ft × 1 ft = 40 cu ft
- Multiply by quantity: 40 cu ft × 4 = 160 cu ft
- Convert to cubic yards: 160 ÷ 27 = 5.93 cu yd
- Convert to 80 lb bags: (5.93 × 27) ÷ 0.6 = 267 bags
- Convert to 60 lb bags: (5.93 × 27) ÷ 0.45 = 356 bags
Result: This job needs about5.93 cubic yards of concrete: 267 bags of 80 lb mix, 356 bags of 60 lb mix, or a small ready-mix delivery.
Tips from the field.
- Dig below the frost line. Footing depth is driven by local frost depth, not just load: check your building department's frost line requirement before finalizing dimensions.
- Rest footings on undisturbed soil. Compacted fill or loose backfill under a footing leads to settling and cracking.
- Order ready-mix above 1 cubic yard. Mixing more than about 27 bags by hand or in a mixer is slow and inconsistent: ready-mix delivery becomes cost-competitive around this volume.
- Add 10% for spillage and over-dig. Hand-dug footings rarely come out to exact dimensions; round your bag or yardage order up.
- Use rebar for structural footings. Two horizontal #4 bars are standard for residential strip footings; verify sizing with your local code or an engineer for anything load-bearing.
Disclaimer: This calculator provides estimates for planning purposes only. Footing size, depth, and reinforcement are structural decisions: consult a licensed structural engineer or your local building department before pouring. PavementCalculator.com assumes no liability for structural failures or material overages.
Cost, price, and density figures on this page reflect approximate U.S. averages as of August 2026 and vary by region, supplier, and material availability.
Frequently asked questions.
How do I calculate concrete for footings?
Multiply the footing length (ft) × width (ft, converted from inches ÷ 12) × depth (ft, converted from inches ÷ 12) to get cubic feet per footing. Divide by 27 to get cubic yards. Multiply by the number of footings for the total. Use our calculator above for instant results: just enter your dimensions.
How many bags of concrete per footing?
For a typical 16-inch wide × 12-inch deep footing that's 30 feet long, you need about 67 bags of 80 lb concrete mix. Each 80 lb bag yields 0.6 cubic feet. A 30 ft × 16 in × 12 in footing = 40 cubic feet ÷ 0.6 = 67 bags. Always add 10% for waste: round up to 74 bags. Use our calculator for your exact footing dimensions.
How deep should concrete footings be?
Footings must extend below the frost line, which ranges from 12 inches in warm climates to 48+ inches in northern states. Minimum footing depth is typically 12 inches. Footings should also rest on undisturbed soil or compacted gravel. Check local building codes for your area's specific requirements.
How wide should a concrete footing be?
Footing width should be at least twice the wall thickness and typically ranges from 12 to 24 inches for residential construction. A standard 8-inch foundation wall requires a 16-inch wide footing. For two-story homes or poor soil conditions, wider footings (20-24 inches) may be required.
What size rebar for concrete footings?
Residential footings typically use #4 (1/2-inch) rebar: two bars placed horizontally, 3 inches from the bottom of the footing. Vertical dowels (#4 or #5) are placed every 4-6 feet to tie the footing to the foundation wall. For heavy-load or seismic areas, larger bars and closer spacing may be required.
How much does a concrete footing cost?
Concrete footings cost $5 to $15 per linear foot on average, including materials, excavation, forms, rebar, and concrete. A typical 150-linear-foot foundation footing costs $750-$2,250. Costs vary by region, soil conditions, footing size, and accessibility.