Deck Footing Calculator

Pick a tube size and get concrete per hole, total bags, and dig depth below your frost line.

Inputs
in
Footings6
in
Results update as you type — no submit
ResultsLIVE
80-lb bags to buy
60 bags
Per footing10 bags
Concrete per hole5.6 cu ft
Total volume1.2 cu yd
Dig depth48 in
Formula
per hole = π × (16 ÷ 24)² × (48 ÷ 12) = 5.6 cu ft
bags = ceil(5.6 ÷ 0.6) × 6 footings = 60
Diagram — footing sectionNTS · IN
GRADE6×6 POSTFROST LINE 42″48″ DEPTH16″ DIATUBE FORM ·FOOTING BELOW FROST
MeasureShedmeasureshed.com/calculator/deck-footing-calculator
Deck footing — material listUNITS: IN · SCALE: NTS
Inputs
Tube diameter16 in
Depth48 in
Footings6
Bag size80 lb
Results
80-lb bags60
Per footing10 bags
Concrete per hole5.6 cu ft
Total volume1.2 cu yd
Footing sectionNTS · IN
GRADE6×6 POSTFROST LINE 42″48″ DEPTH16″ DIATUBE FORM ·FOOTING BELOW FROST
Shopping list
☐ 60 × 80 lb bags concrete
☐ 6 × 16 in tube forms
Formula
per hole = π × (16 ÷ 24)² × (48 ÷ 12) = 5.6 cu ft
total = 5.6 × 6 = 33.5 cu ft = 1.2 cu yd
bags = ceil(5.6 ÷ 0.6) × 6 = 60
Estimates for planning only — verify before purchaseSHEET 1 OF 1
How it works

A tube footing is a cylinder, so the concrete per hole is π × radius² × depth. Diameter is in inches and depth is in inches, so the calculator works in feet under the hood and returns cubic feet per hole. Multiply by the number of footings for the total, then divide by the bag yield and round up.

Bags round up per hole, not across the whole job — you mix and pour each footing before moving on, so a partial bag left over at one hole rarely carries to the next. That is why the total is the per-hole bag count times the number of footings.

Depth is set by your frost line, not by the load. The bottom of the footing has to sit below the depth to which the ground freezes, plus a few inches of bearing, or frost heave will lift the deck every winter. Your building department publishes the frost depth for your area.

Worked example
Tube 16 in dia · depth 48 in · 6 footings · 80 lb bags
per hole = π × (16 ÷ 24)² × (48 ÷ 12) = 5.6 cu ft
bags per hole = ceil(5.6 ÷ 0.6) = 10 → total = 10 × 6 = 60
Questions from the jobsite
Below your local frost line — commonly 36–48 in in the northern US, less in the south — plus about 6 in of bearing. Your building department publishes the exact frost depth; it governs, not any rule of thumb.
SOURCES — IRC R403 footings · DCA 6 deck construction guide
Footing depth and size are set by local code — confirm with your building department before digging.
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