Deck Post & Footing Depth Calculator
Calculate Sonotube diameter, frost line depth, concrete bags per hole, and post anchor brackets for deck piers.
Input Parameters
Enter dimensions and specifications to estimate materials.
80 lb Concrete Bags Needed
Total Concrete Volume
0.93cu yd
60 lb Bags (alternative)
56bags
Hole Depth Each
42in
Concrete per Footing
3.1cu ft
Gravel Base
400lbs
Post Base Brackets
8brackets
Material estimates include recommended trade waste buffer. Always confirm dimensions on site prior to ordering.
How The Calculation Works
Formulas, material coverage assumptions, waste buffers, and rounding standards.
Hole depth is frost depth plus the height you want the tube standing above grade โ the footing base must sit below the frost line or the deck will heave and settle with each freeze cycle.
Concrete volume is the cylinder area times total depth, converted to 60 lb and 80 lb bag equivalents so you can compare bagged mix against ordering ready-mix.
A flared base spreads the bearing load over a wider area of soil, which matters on soft ground; it also adds roughly 40% to the concrete for that footing.
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Frequently Asked Questions
Practical installation guidance and purchasing tips for deck post & footing depth calculator.