Concrete Deck Footing Calculator
A standard 12-inch diameter deck footing at 48 inches deep needs about 6 bags of 80-lb concrete. A typical 12×16 ft deck with 6 footings needs 36 bags total. Enter your footing dimensions and count below for the exact number.
Pro Tips
- →Deck footings must extend below frost line
- →Typical footing diameter is 12 inches for deck posts
- →Set posts on concrete piers above footing
- →Number of footings depends on deck size and span
- →Check local codes for specific requirements
Includes 10% waste factor
That's typically a professional pour. See costs ↓
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Cost Estimate
Estimated material costs for your project
Recommendation: Bagged Concrete
For smaller projects, bagged concrete gives you more control and less waste.
26 bags × 80lb
0.58 cubic yards + delivery
Prices vary by location and time. Contact local suppliers for accurate quotes.
For general step-by-step instructions, read our complete When To Use Rebar and Permit Requirements.
Deck Footing Requirements
Every deck footing must extend to or below the local frost line — a footing installed above the frost line will heave during freeze-thaw cycles, warping the deck frame and potentially failing a permit inspection.
| Region | Frost Line Depth | Min Footing Depth |
|---|---|---|
| Deep South (FL, GA, LA) | 0–6 in | 18 in minimum |
| Mid-Atlantic, Pacific Coast | 12–24 in | 24–30 in |
| Midwest, Upper South | 30–42 in | 36–48 in |
| Northern states (MN, WI, ME) | 42–60 in | 48–66 in |
Local building codes are authoritative — check with your building department before digging. Most jurisdictions require footings to bear on undisturbed native soil, not backfill.
Footing Diameter by Load
Standard residential deck footings are 12 inches in diameter for single-story decks with post spacing of 8 feet or less. Use 14–16 inch footings for larger decks, multi-story structures, or decks that will support a hot tub. A full hot tub can weigh 6,000–8,000 lbs — that load transfers directly to the footings.
| Footing Diameter | Depth | Bags (80-lb) | Application |
|---|---|---|---|
| 10 in | 36 in | 3–4 bags | Pergola, light structure |
| 12 in | 48 in | 6 bags | Standard residential deck |
| 12 in | 60 in | 7–8 bags | Deep frost-line zone |
| 16 in | 48 in | 11 bags | Heavy deck, multi-story |
| 16 in | 60 in | 13 bags | Hot tub support |
A 12×16 ft deck with 6 footings (12 in diameter, 48 in deep) needs approximately 36 bags of 80-lb concrete. At that volume, bagged concrete is practical — a full deck footing job typically takes a half day.
Post-to-Footing Connection
Never embed posts directly into concrete — the connection will rot within 10–15 years regardless of pressure treatment. The correct method:
- Pour the footing flush with or slightly above grade
- While the concrete is still wet, press a post base anchor (Simpson Strong-Tie ABU44 or equivalent) into the footing and check alignment
- Let concrete cure 48 hours before attaching posts
- Bolt or screw the post into the anchor using structural fasteners per the anchor manufacturer's specifications
Post base anchors elevate the post bottom off the concrete surface, allowing water to drain away from the end grain and extending post life to 40+ years in most climates.
For tube-form (sonotube) footings, see our Sonotube Calculator. For fence and mailbox post holes, use our Post Hole Calculator.