Deck footing calculator
Work out how many footings a deck needs and the concrete to pour them.
Deck footing calculator
Work out how many footings a deck needs and the concrete to pour them.
Enter your deck dimensions to see the footing count.
Footings needed
Project summary
How it works
These are material estimates, not a structural design. Footing size and depth depend on soil bearing capacity, load and frost depth; check local code before building.
Deck footing calculator
Footings follow the same beam and post grid as the deck itself
This calculator uses the same beam and post layout the general deck material calculator uses for its framing: beams run along the deck length at a spacing you choose, and posts support each beam at a spacing along the deck width. Every beam-and-post intersection is a footing, so the footing count is the beam count multiplied by the posts per beam.
Footing size is a site condition, not a formula
Unlike the beam and post count, footing diameter and depth are not something this calculator derives: soil bearing capacity, the load the deck carries and local frost depth all determine what a footing actually needs to be, so this tool asks for those dimensions directly rather than assuming a value.
Frequently asked questions
How many footings does a 16 by 12 foot deck need?
At 8 foot beam and post spacing, a 16 by 12 foot deck needs 3 beams and 3 posts per beam, for 9 footings total. Wider spacing means fewer footings but larger beams and posts to carry the load; enter your own dimensions above for the exact count.
How deep should a deck footing be?
Footing depth is set primarily by the local frost line so it does not heave in freeze-thaw cycles, and is determined by local building code rather than a fixed number. Check with your local building department for the required footing depth before digging.
How many footings does a 12 by 16 foot deck need?
A typical layout has one footing at each corner plus intermediate footings at 6 to 8 foot intervals along the beam lines. For a 12 by 16 foot deck, that is usually 6 footings arranged in two rows of three. The calculator gives you a count based on your beam spacing and deck dimensions.
How deep should deck footings be?
Footings must extend below the frost line, which varies by region. In northern climates that can be 4 feet or more. In southern areas it may be 12 to 18 inches. Check your local building code for the frost line depth in your area. The calculator counts footings, and you dig to the depth your code requires.
What size footings does a deck need?
Most residential decks use 12 inch diameter concrete tube footings, often called sono tubes. Larger decks or heavier loads may require 16 or 24 inch footings. The footing size depends on the load and the soil bearing capacity. Your local building code specifies the minimum footing size. The calculator counts footings, and you select the diameter that matches your code.
Do I need footings for a ground level deck?
Even low decks benefit from footings at post locations. A ground level deck sitting directly on the ground will rot and shift over time. Concrete deck blocks or poured footings keep the posts out of contact with the soil and distribute the load. The calculator counts footings regardless of deck height.
How many bags of concrete per footing?
A 12 inch diameter footing that is 4 feet deep takes about four to five 60 pound bags of concrete mix. A 24 inch diameter footing at the same depth takes roughly 12 to 15 bags. The calculator counts footings, and you can estimate the concrete volume based on the diameter and depth your code requires.
Can I use precast deck blocks instead of poured footings?
Precast deck blocks work for freestanding ground level decks in many jurisdictions. They sit on compacted gravel and accept 4 by 4 or 6 by 6 posts directly. They are not suitable for all soil conditions or for elevated decks that require inspected poured footings. Check your local building code before choosing this option.