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Deck Footing Calculator

Calculate deck footing materials — posts, panels or boards, spacing and waste for US deck & fence projects. Enter dimensions, select units and add waste to get instant, supplier-ready numbers.

1. Measurements & Dimensions

2. Material Properties & Waste Allowance

3. Optional Material Cost

DECK FOOTING CALCULATOR ESTIMATE
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Enter dimensions above to calculate

Calculation Breakdown & StepsFormula: Concrete = post count × fill depth × (π × hole diameter²/4 − square post width²); bags = ceil(concrete × allowance factor / bag yield).
  1. Enter values to see step-by-step substitution.

    Engineering Assumptions:

    • A centered square post in a cylindrical hole. The post occupies the full concrete fill depth. Gravel below the concrete is excluded.
    • Hole size, embedment and suitability of concrete depend on the project design and local conditions; this tool only estimates material.
    VISUAL GUIDE — DECK FOOTING CALCULATORdeck-fence · deck-footing-calculator

    Deck Footing — 5.5" boards + gap

    Deck Footing Calculator deck21×8 ft — Deck Footing · 18 boards
    Deck Footing Calculator — Concrete = post count × fill depth × (π × hole diameter²/4 − square post width²); bags = ceil(concrete × allowance factor / bag yield). · example 21×8 @4in = 56.0 ft³ (2.07 yd³) → 2.22 yd³ with 7% waste · deck-footing-calculator

    What Is This Calculator?

    The Deck Footing Calculator — Builds US decks and fences — boards, joists, posts, panels and concrete with waste.

    What Does It Calculate?

    • Deck boards and joists
    • Fence posts, panels and rails
    • Concrete bags per post

    How to Use the Calculator

    1. Measure Fence 100 ft, post spacing 8 ft, picket 5.5 in + 0 in gap — use feet for length/width and inches for thickness where typical.
    2. Enter values and select units. The calculator converts to feet before calculating (inches /12, yards x3).
    3. Adjust waste % and optional price, then click Calculate. Results show with waste included.
    4. Use Reset to clear and try another size.

    Formula & Engineering Methodology

    Concrete = post count × fill depth × (π × hole diameter²/4 − square post width²); bags = ceil(concrete × allowance factor / bag yield).

    • Length — Fence/deck length
    • Spacing — 8 ft post, picket gap 0-0.5 in

    All units convert to exact standard engineering dimensions (NIST SP 811) before calculation to ensure consistency between US Customary and Metric measurements.

    Worked Example

    Example: Fence 100 ft, post spacing 8 ft, picket 5.5 in + 0 in gap

    STEPVALUE
    Postsceil(100/8)+1 =14
    Pickets1200 in /5.5 =218
    With waste236 pickets

    Construction Information

    Material: Deck boards 5.5 in + 1/8 in gap, joists 16 in o.c. Fence posts 8 ft spacing, 2.5 ft deep, 0.5 bag 50-lb per post.

    Posts 8 ft OC, 1/3 buried below frost line. Gate needs 2 extra posts.

    Material Information

    Deck boards 5.5 in + 1/8 in gap, joists 16 in o.c. Fence posts 8 ft spacing, 2.5 ft deep, 0.5 bag 50-lb per post.

    Waste & Overages

    Add 10% for cuts and angles — 15% for curves.

    Practical Tips

    • Crown deck boards up
    • Set posts in gravel + concrete for drainage

    Common Mistakes

    • Wrong gap — boards buckle
    • Shallow posts — frost heave

    Assumptions & Engineering References

    • A centered square post in a cylindrical hole. The post occupies the full concrete fill depth. Gravel below the concrete is excluded.
    • Hole size, embedment and suitability of concrete depend on the project design and local conditions; this tool only estimates material.

    This calculator provides an estimate based on your inputs. Actual requirements vary by site, material and installation. For code-regulated or load-bearing work, consult a qualified professional.

    Calculations run 100% in your browser — zero tracking of your dimensions or input data.

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    Frequently asked questions

    What does the Deck Footing Calculator calculate?

    The Deck Footing Calculator estimates deck footing quantity for US jobs — Deck boards and joists, Fence posts, panels and rails, Concrete bags per post. Enter dimensions, choose units, add waste and price to get instant results.

    How do I measure for deck footing?

    Measure fence 100 ft, post spacing 8 ft, picket 5.5 in + 0 in gap on site. Use the unit selectors — the tool converts inches→feet (÷12) and yards→feet (×3) before math. For non-rectangular, split into rectangles and add.

    How much waste should I add?

    Add 10% for cuts and angles — 15% for curves.

    How accurate is this deck footing estimate?

    Math is exact for your inputs. Actual needs vary by site, material and installation. Add 5–10% waste for rectangular, 10–15% for irregular.

    About Calculator Street

    Built by Vipul Otari for US homeowners & contractors. Calculator inputs are processed in your browser. Estimates depend on your measurements, product specifications and the assumptions shown on this page. Confirm order quantities with your supplier and structural requirements with your project designer. Page updated: 2026-09-11.

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