MyYardCalc
Lumber & Woodworking · Material planning

Decking Calculator

Estimate deck boards for a rectangular layout using actual board width, gaps, direction and stock length. See allowance and cutting assumptions.

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US & metric

Example values are filled in. Replace them with your measurements.

ft
ft
ft
in
in
%

An editable purchasing margin, not a measured compaction rate.

$

Enter your measurements

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The calculation

Rows = ceil((cross-deck width + side gap) ÷ (board width + side gap)). Multiply by stocks per row and allowance.

  • Straight decking only; offcuts are not reused between rows. Framing and stair materials are excluded.

Saved on this device

Only estimates you choose to save are stored here.

    Measure with a little context

    How to use this decking calculator

    Use actual board width and the gap recommended for that material and installation condition. Choose the direction before estimating board rows.

    Stock is counted for each row without reusing offcuts across rows. This excludes framing, stairs, picture-frame borders, fastening and structural design.

    Rows = ceil((cross-deck width + side gap) ÷ (board width + side gap)). Multiply by stocks per row and allowance.

    A worked example

    With the example values shown below, the calculated result is 29 boards. These are demonstration inputs, not installation specifications.

    View the example measurements
    • Deck length: 16 ft
    • Deck width: 12 ft
    • Board stock length: 16 ft
    • Actual board width: 5.5 in
    • Side gap: 0.125 in
    • Extra allowance: 10 %

    From estimate to order

    Whole packages and pieces round up; measured lengths, areas and volumes keep full precision during calculation. Match the product dimensions and units to your quote, and check cuts, minimum orders and delivery before purchasing.

    Read our formulas, rounding rules and limitations →

    Decking planning questions

    Why does deck-board direction change the result?

    Direction determines the length of each board run and the width across which rows are counted. With a fixed stock length, turning the boards can change both joints per row and the total stock count. Use the layout that matches your intended framing and installation.

    Is this a complete deck material or cost calculator?

    No. It estimates surface boards and optional board cost. Joists, beams, posts, stairs, railings, fasteners and structural spans are separate. Offcuts are not reused across rows, so a detailed cutting plan can change the final purchase quantity.

    Calculation notes updated . Formulas, sources and limitations.

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