Deck Footing Calculator
Deck footings must extend below the frost line and be sized to distribute the deck load to the soil. Enter deck area, post spacing, and soil bearing capacity to get footing diameter, depth, concrete bags per footing, and total material cost.
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How to Use This Calculator
- 1Enter your measurements in the fields above. Use the units shown next to each field (ft, in, etc.).
- 2Click Calculate to get your material estimate instantly.
- 3Review the highlighted result — it shows the key quantity you need to order.
- 4Use Copy Results to save your estimate, or bookmark the URL — your inputs are encoded in the link.
Pro tip: Always add 10% to your material order to account for waste, cuts, and defects.
Frequently Asked Questions
How deep should deck footings be?
Deck footings must extend at least 6 inches below the local frost depth. In areas with no frost (Southern states), 12 inches is the minimum. Check your local building code — many jurisdictions require footings at 36" or deeper in the Midwest and Northeast.
What size footing tube form do I need?
Most residential decks use 10" or 12" diameter tube forms. For heavier loads (hot tubs, multi-level decks, or spans over 10 feet), use 16" or 18" diameter footings. The footing diameter depends on the tributary area it must support divided by soil bearing capacity.