Concrete Pier Footing Calculator
Building pier footings? Calculate concrete needs with our free tool. Get accurate estimates for pier foundations.
Pro Tips
- →Pier footings must extend below frost line
- →Typical pier diameter is 12-18 inches
- →Top with concrete piers or blocks above grade
- →Include rebar in center of each pier
- →Space piers according to beam span 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.
35 bags × 80lb
0.77 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.
What a Pier Footing Actually Is
A pier footing is a two-part foundation unit: a wide, flat spread footing pad at the bottom and a vertical pier (column) rising from it to support a beam, post, or framing above. The pad spreads the load across enough soil area to prevent settling; the pier carries that load down to the pad while keeping the wood structure above grade.
This differs from a plain drilled pier (a single straight cylinder, covered by our sonotube calculator) and from a standalone spread footing under a wall (covered by our footing calculator). A pier footing combines both into one pour, and it is the standard foundation for decks, porches, raised post buildings, pergolas, and pole barns.
| Part | Shape | Typical Size | Job |
|---|---|---|---|
| Spread footing pad | Square or round | 18–24 in wide, 8–12 in thick | Distributes load to soil |
| Pier / column | Cylinder or square | 8–16 in diameter | Carries load, lifts structure above grade |
| Dowels / rebar | Vertical #4 bars | Full height | Ties pier to pad and post above |
For deck-specific spacing and beam tributary areas, use the dedicated deck footing calculator.
How to Calculate Pier Footing Volume
Total concrete per pier footing is simply the footing pad volume plus the pier volume. Calculate each separately, then add.
- Footing pad (square): length × width × thickness
- Footing pad (round): π × radius² × thickness
- Pier (cylinder): π × radius² × height
Worked example — 24-in square pad + 12-in pier, 36 in tall:
- Pad: 24 in × 24 in × 10 in = 5,760 cu in = 3.33 cu ft
- Pier: π × (6 in)² × 36 in = 4,072 cu in = 2.36 cu ft
- Total: 3.33 + 2.36 = 5.69 cu ft = 0.21 cubic yards per pier footing
For 8 of these piers that is about 1.7 cubic yards before waste, or roughly 1.85 cubic yards with the standard 10% allowance. The calculator above handles both the pad and the pier in one step — enter your dimensions and quantity to skip the arithmetic.
Concrete and Bag Count per Pier Footing
The table below pairs common footing pad sizes with pier diameters at a 36-inch pier height (a typical frost-depth embedment). Bag counts assume 80-lb mix at 0.6 cu ft yield, rounded up, with no waste added — add 10% for spillage and over-dig.
| Pad (square) | Pier dia. | Pad vol. | Pier vol. | Total per pier | 80-lb bags |
|---|---|---|---|---|---|
| 18×18×8 in | 8 in | 1.13 cu ft | 1.05 cu ft | 2.18 cu ft | 4 |
| 20×20×10 in | 10 in | 2.31 cu ft | 1.64 cu ft | 3.95 cu ft | 7 |
| 24×24×10 in | 12 in | 3.33 cu ft | 2.36 cu ft | 5.69 cu ft | 10 |
| 24×24×12 in | 12 in | 4.00 cu ft | 2.36 cu ft | 6.36 cu ft | 11 |
| 30×30×12 in | 14 in | 6.25 cu ft | 3.21 cu ft | 9.46 cu ft | 16 |
Once a single pier footing climbs past about 12 bags, mixing by hand stops making sense. For more than roughly 1 cubic yard total across all piers, a short-load ready-mix delivery is usually cheaper and far faster — see the concrete cost calculator to compare bagged versus delivered pricing for your pier count.
Sizing the Footing Pad by Load and Soil
The pad's job is to keep soil pressure below the soil's bearing capacity. The IRC presumes 1,500 psf for the weakest soils unless a soil test proves higher (IRC Table R401.4.1, presumptive load-bearing values). Required pad area = total load on the pier ÷ allowable soil bearing.
For decks, the IRC deck provisions size footings directly from tributary area (IRC R507.3 and Table R507.3.1, footing size for decks). A pier carrying a 50 sq ft tributary area on 1,500-psf soil needs roughly a 24×24-inch footing.
| Tributary load (per pier) | Soil 1,500 psf | Soil 2,000 psf | Soil 3,000 psf |
|---|---|---|---|
| 2,000 lb | 16×16 in | 14×14 in | 12×12 in |
| 3,000 lb | 18×18 in | 16×16 in | 14×14 in |
| 4,500 lb | 22×22 in | 19×19 in | 16×16 in |
| 6,000 lb | 24×24 in | 22×22 in | 18×18 in |
These are guideline sizes; always confirm against your local code and tributary-area calculation. When in doubt, a structural engineer's stamp is cheap insurance against a settling deck.
Frost Depth and Embedment
The most common pier-footing failure is frost heave — soil water freezes, expands, lifts a shallow footing, then drops it unevenly on thaw. To prevent it, the bottom of the footing must sit below the local frost line (IRC R403.1.4, footings below frost line). That is why pier height in your volume calc is usually dictated by frost depth, not by how far above grade the post must sit.
| Region / climate | Typical frost depth | Common pier height |
|---|---|---|
| Deep South / coastal | 0–12 in | 12–24 in |
| Mid-Atlantic / Midwest | 24–36 in | 36–42 in |
| Northern / mountain | 42–60 in | 48–60 in |
Check your jurisdiction's adopted frost depth before ordering tube forms — it sets both the hole depth and your concrete volume. Permitting offices publish this number; our permit requirements guide explains how to find and document it.
Rebar, Dowels, and Tube Forms
Most codes require at least one vertical #4 rebar running the full pier height, with dowels bent into the footing pad so the pad and pier act as one unit. Larger piers use 2–4 vertical bars tied with horizontal hoops. The pier top receives an anchor bolt or standoff post base so the wood post never touches concrete. Our rebar guide covers bar sizing and placement.
For the form work, the pier is usually poured in a cardboard tube (Sonotube), while the pad is formed in the bottom of the hole or in a plastic bell base such as a Bigfoot footing form that slips over the tube to create the spread pad in one pour. Building square pads from lumber instead? The form-building guide walks through bracing them against the wet-concrete pressure.
| Form type | Best for | Notes |
|---|---|---|
| Cardboard tube only | Pier with hand-dug pad | Cheapest; form the pad separately |
| Tube + bell base | Combined pad + pier, one pour | Fast, consistent pad area |
| Lumber-framed square pad | Shallow / wide pads | More labor, full size control |
How Many Piers Does Your Structure Need
Pier count comes from beam span and load, not guesswork. Typical residential spacing runs 6–8 ft on center along beams, tightened where loads concentrate.
| Structure | Approx. size | Typical pier count |
|---|---|---|
| Small deck | 10×12 ft | 4–6 |
| Mid-size deck | 16×20 ft | 6–9 |
| Covered porch | 12×16 ft | 6–8 |
| Pole / post building | 24×30 ft | 12–15 |
Multiply your per-pier volume from the tables above by this count, add 10% waste, and you have your order. Ready to size your piers? Enter your pad and pier dimensions in the calculator at the top of this page to get exact concrete volume and bag count, then cross-check deck-specific spacing with our deck footing calculator.