Concrete Footing Calculator
Total run × width × depth, with the right waste factor for trench or formed pours. Sizing guidance follows IRC Chapter 4.
MaterialsCalc Editorial TeamConstruction Estimating EditorsJuly 15, 2026Contents
Footing sizes that pass inspection
Footing dimensions come from the code table, not from the concrete budget.
| Supporting | Minimum width | Typical section |
|---|---|---|
| 1-story wood frame | 12 in (305 mm) | 12 × 6 inOn ≥1,500 psf soil |
| 2-story wood frame | 15 in (380 mm) | 16 × 8 inMost common residential pour |
| 3-story / brick veneer | 18–23 in | 20 × 10 inVerify bearing capacity |
| Garden / landscape walls | 2 × wall thickness | 16 × 8 in for 8 in wallBelow frost line |
| Deck beams (continuous) | Per span tables | Use column calc for piersPiers are more common |
The footing volume formula
V = Run × Width × Depth × (1 + waste)
- Run
- total length of all footings (ft or m)
- Width
- footing width (in or mm)
- Depth
- footing thickness (vertical) (in or mm)
- waste
- 0.10 formed · 0.15 earth-formed
For a rectangular building, Run = 2 × (length + width). Interior bearing walls add their own runs — walk the foundation plan and sum every footing line.
Worked example: house perimeter footing
A 40 × 28 ft house with one 28 ft interior bearing wall. Footings are 16 in wide × 8 in deep, earth-formed in clean trenches.
- 1
Perimeter run
2 × (40 + 28) = 136 ft
- 2
Add interior bearing wall
136 + 28 = 164 ft total run
- 3
Convert section to feet
16 in = 1.333 ft · 8 in = 0.667 ft
- 4
Gross volume
164 × 1.333 × 0.667 = 145.8 ft³
- 5
Add 15% (earth-formed) and convert
145.8 × 1.15 ÷ 27 = 6.21 yd³
Result: Order 6.5 yd³. One truck, one pour, no cold joints in the foundation.
What goes wrong in trench pours
Footings feed directly into wall volume — if you're pouring a stem wall or full foundation wall on top, run the wall calculator next and schedule both pours with the plant at once. Plants discount combined orders more often than you'd think; see the cost guide for how delivery fees stack.
Frequently asked questions
Estimating the whole foundation?
Footings, walls and a slab each take two minutes — then hand the plant one combined order.
Open the Concrete CalculatorFoundation reading list
Sources & references
- [1]2021 International Residential Code, Ch. 4: Foundations — International Code Council, 2021
- [2]ACI 318-19: Building Code Requirements for Structural Concrete — American Concrete Institute, 2019
- [3]IS 456:2000 — Plain and Reinforced Concrete: Code of Practice — Bureau of Indian Standards, 2000
Concrete Footing Calculator
Continuous (strip) footings for foundations, garden walls and deck beams. Enter the total run length.