Deck Footing Calculator
Estimate deck footing count from beam rows and post spacing, then calculate cylindrical footing concrete, bags, drilled depth and cost.
Default project preview
10 footings
Concrete order
1.71 yd³
Concrete bags
77
Actual grid spacing
5 ft
Total drilled depth
30 ft
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Deck length along beams
Enter this project assumption in ft. The current imperial default is 20 ft.
Supported beam rows
Enter this project assumption in a unitless value. The current imperial default is 2. Minimum: 1.
Maximum post spacing
Enter this project assumption in ft. The current imperial default is 6 ft.
Footing diameter
Enter this project assumption in in. The current imperial default is 16 in.
Concrete depth
Enter this project assumption in ft. The current imperial default is 3 ft.
Extra allowance
Enter this project assumption in %. The current imperial default is 10 %. Minimum: 0. Maximum: 50.
Concrete yield per bag
Enter this project assumption in ft³. The current imperial default is 0.6 ft³.
Ready-mix price
Enter this project assumption in per yd³. The current imperial default is 165 per yd³. Minimum: 0.
Price per bag
Enter this project assumption in a unitless value. The current imperial default is 7. Minimum: 0.
How to read the outputs
Concrete order
allowance included. Default preview: 1.71 yd³.
Concrete bags
rounded full bags. Default preview: 77.
Actual grid spacing
equal spacing along beam. Default preview: 5 ft.
Total drilled depth
all footing holes. Default preview: 30 ft.
Posts per beam row
includes both ends. Default preview: 5.
Cost comparison
ready-mix / bags. Default preview: $281.58 / $539.00.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Positions per beam row = round up (deck length ÷ maximum spacing) + 1. Total footings = positions × beam rows. Concrete uses cylindrical footing volume.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: July 29, 2026
Use this calculator to estimate concrete volume and material count for deck footings after the footing diameter, depth and quantity have been established by the project design. It does not size footings or determine allowable soil bearing.
Calculation steps
- 1Confirm footing count from the framing layout.
- 2Enter the specified diameter and concrete depth.
- 3Calculate cylindrical volume for every footing.
- 4Add allowance and round to ready-mix or bag yield.
Worked numerical example
Eight cylindrical footings, each 12 in diameter and 36 in deep, contain about 18.85 ft³ or 0.70 yd³ total. Adding 10% allowance gives roughly 0.77 yd³.
Purchasing and rounding
Concrete is rounded according to bag yield or supplier volume increments. Do not assume excavated hole volume equals concrete volume when forms, bells or gravel bases are used.
Interpret the result
The quantity result cannot validate footing depth, frost protection, uplift resistance or post-base connection.
Page-specific assumptions
- Cylindrical straight-sided footings.
- Uniform dimensions.
- No deduction for reinforcement or post bases.
- No enlarged bell unless modeled separately.
Common mistakes
- Using hole diameter instead of formed concrete diameter.
- Including gravel base as concrete depth.
- Selecting footing size from deck area alone.
- Ignoring local frost and soil requirements.
Primary and technical references
BuildMeter provides planning estimates, not engineering, architectural, electrical, mechanical, plumbing, permit or code approval. Review the methodology and verify final decisions with product documentation and qualified professionals.
BuildMeter Guides
Understand the measurements and assumptions
Use these visible reference guides before changing project inputs or planning allowances.
FAQ
Deck Footing Calculator questions
Why is one added to the spacing calculation?+
A run divided into spaces needs a support position at both ends, so positions are one more than the number of spaces.
Does this size footing diameter?+
No. Diameter depends on tributary load, soil bearing, frost conditions and local code.
Can every beam row use the same spacing?+
Only when the approved structural design permits it. Loads and beam spans may require a different layout.