Free Deck Footing Calculator
Calculate how many footings you need for a deck based on beam span, joist span, and footing spacing requirements.
Maximum spacing between footings along beam
Spacing between beam rows (perpendicular to joists)
Total Footings
9
Total Footings vs Deck Length
How to Calculate Deck Footings
Formula
Beam Rows = floor(Deck Width / Beam Spacing) + 1
Footings per Row = floor(Deck Length / Footing Spacing) + 1
Total Footings = Beam Rows × Footings per Row
Concrete per Footing = pi × r² × depth / 27
Footing spacing is typically 6-8 ft for 2×8 beams or 8-10 ft for doubled 2×10 or 2×12 beams. Footing depth must extend below the frost line per local building code.
Example Calculation
A 16×12 ft deck with 8 ft footing spacing, 6 ft beam spacing, 12-inch diameter footings 42 inches deep.
- 01Beam rows = floor(12 / 6) + 1 = 3 rows
- 02Footings per row = floor(16 / 8) + 1 = 3 footings
- 03Total footings = 3 × 3 = 9 footings
- 04Footing radius = 12 / 2 / 12 = 0.5 ft
- 05Concrete per footing = 3.14159 × 0.5² × 3.5 / 27 = 0.102 cu yd
- 06Total concrete = 9 × 0.102 = 0.92 cu yd
Frequently Asked Questions
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