Deck Post Quantity Calculator
Estimate preliminary deck-post positions, total posts and footing allowance from deck length, beam-row count, target spacing and end setbacks.
Default project preview
14 posts
Beam rows
2
Posts per row
6
Calculated spacing
6 ft
Supported beam length
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 beam
Enter this project assumption in ft. The current imperial default is 32 ft.
Post-supported beam rows
Enter this project assumption in a unitless value. The current imperial default is 2. Minimum: 1.
Target post spacing
Enter this project assumption in ft. The current imperial default is 6 ft.
Post setback at each end
Enter this project assumption in ft. The current imperial default is 1 ft. Minimum: 0.
Extra or special posts
Enter this project assumption in a unitless value. The current imperial default is 2. Minimum: 0.
Price per post
Enter this project assumption in a unitless value. The current imperial default is 38. Minimum: 0.
Footing allowance per post
Enter this project assumption in a unitless value. The current imperial default is 72. Minimum: 0.
How to read the outputs
Beam rows
post-supported rows. Default preview: 2.
Posts per row
5 spaces. Default preview: 6.
Calculated spacing
between post centers. Default preview: 6 ft.
Supported beam length
between end setbacks. Default preview: 30 ft.
Footing allowance
entered amount per post. Default preview: $1,008.00.
Posts and footings
preliminary materials allowance. Default preview: $1,540.00.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Usable beam length = deck length − two end setbacks. Spaces are rounded up from target spacing; posts per row = spaces + 1.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: August 19, 2026
Estimate the number of deck support posts from beam runs and the selected post spacing for preliminary layout planning.
Calculation steps
- 1Measure each beam or support line separately.
- 2Enter the maximum planning spacing between posts.
- 3Divide each support run into spans that do not exceed that spacing.
- 4Count the required support points, including ends where posts are actually specified.
Worked numerical example
A 24 ft beam with posts at a maximum 6 ft spacing needs support points at 0, 6, 12, 18 and 24 ft, for five posts along that beam before accounting for any engineered end condition.
Purchasing and rounding
Purchase posts only after the beam layout, footing locations and post size are confirmed by the project design. Post count is not a substitute for footing size, beam sizing, lateral bracing or connection design.
Interpret the result
The result is a preliminary support-point count based on spacing. Shorter spacing can increase the count, while cantilevers or engineered beam details can change where posts are required.
Page-specific assumptions
- Posts are placed along defined beam/support lines.
- The entered spacing is a project-approved maximum, not a code value invented by the calculator.
- End supports are counted only where the chosen framing layout requires posts.
Common mistakes
- Using joist spacing as post spacing.
- Counting deck corners instead of actual beam support points.
- Ignoring beam cantilevers or offsets.
- Treating the count as structural approval.
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 Post Quantity Calculator questions
Can posts always be spaced at the entered distance?+
No. Structural beam spans and loads determine the maximum permitted spacing.
Why include extra posts?+
Stairs, beam splices, landings, corners or concentrated loads may need additional support.
Does the calculator size footings?+
No. Footing dimensions depend on loads, soil, frost depth and local requirements.