Deck Footing Size & Depth Calculator
Each deck post carries a tributary slice of the deck down to a footing. This calculator works out the load on each footing, the bearing area it needs over your soil, how deep it must go below the frost line in your state, and how much concrete to buy.
Member sizes read from the IRC R507.6 (joists) and R507.5 (beams) tables for No. 2 Southern Pineat 40 psf live + 10 psf dead. Footings from tributary load ÷ soil bearing (R507.3); ledger fasteners per R507.9. Confirm with your local building department.
| Decking — Pressure-treated pine192 sq ft · ~28 × 16′ boards | $575–$1,730 |
| Substructure (joists, beam, posts, hardware)192 sq ft framing | $1,150–$2,495 |
| Footings (concrete piers)4 posts | $140–$360 |
| Railing / guard40 lin ft | $600–$2,400 |
| Stairs4 treads | $120–$380 |
| Permit + fasteners + miscallowance | $75–$500 |
| Total estimate | $2,660–$7,865 |
Low = DIY material budget; high = contractor-installed (labor included). Regional prices vary — treat as a planning range, not a quote.
Deck Footing — what to know
- •Footing area = post load ÷ soil bearing. The default 1,500 psf is the IRC presumptive value for sand/silt/clay; gravel can bear far more.
- •The footing bottom must sit below the local frost line so it can't heave — that's why a Minnesota footing is 5 ft deep and a Florida one is 12".
- •Concrete per pier = π × radius² × depth; an 80-lb bag of mix yields about 0.6 cubic feet. Even frost-free regions need at least 12" to reach undisturbed soil.
Want a permit-ready deck plan?
This estimate is built for planning. For your permit packet, DeckCalc HQ Pro turns these numbers into a stamped framing plan, footing schedule and material list as a printable PDF.
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