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Decking Calculator

Estimate stock deck boards from actual widths, gaps, orientation and an explicit no-offcut-reuse model.

Your numbers

Make it your own
Updates as you type
Stock boards to order
58boards

Calculated from your inputs · rounded for display

Rows across deck26
Stock pieces per row2
Deck area240ft²
Board material cost$1,044.00

Actual board dimensions. Butt joints assumed; no offcut reuse across rows. Framing, clips, stairs and structural suitability are excluded.

Your calculation, step by step

No black boxes
  1. Rows = ceil((cross dimension in inches + gap) / (actual board width + gap)).
  2. Each row needs ceil(20 / 16) stock pieces; add entered waste and round up.

What if things were different?

Save up to three scenarios, then change your inputs to compare the possibilities.

How to use this calculator

  1. Enter your own values in the labeled fields. Check the units and assumptions before comparing results. Only the fields needed for your selected calculation mode are shown.
  2. Your answer updates automatically. Review the calculation steps to see exactly how it was calculated.
  3. Copy, share, save, or download your result. Saved inputs stay on this device.

How the calculation works

Rows=ceil((cross span+gap)/(board width+gap)); boards=ceil(rows × pieces/row × allowance)

Board widths are actual sizes, not nominal names. Rows run in the selected direction. Each row uses whole stock pieces; the model does not reuse cut-offs across rows and can overestimate purchases when an optimized cutting plan is available. Review the units, period and assumptions before comparing scenarios. Displayed values are rounded, while the underlying calculation retains its available precision.

A worked example

A 10 × 10 ft deck using 6-inch-wide boards, no gaps, 10-ft stock and no allowance uses 20 boards.

Reading your result

Use the main result together with its units and supporting figures. Display values are rounded; calculations keep their underlying precision. A change in inputs or assumptions can change the answer. Compare the step-by-step working with your intended use before relying on an estimate.

Frequently asked questions

What assumptions does this calculation use?

Board widths are actual sizes, not nominal names. Rows run in the selected direction. Each row uses whole stock pieces; the model does not reuse cut-offs across rows and can overestimate purchases when an optimized cutting plan is available.

Can I save or check a scenario?

The result includes the working and supporting values. Save and Restore keep inputs on this device; Copy, Download and Print export the result. Sharing a scenario explicitly includes the inputs in its link.

Sources & methodology

This calculator uses the mathematical identity and assumptions stated above. No current rates, prices, or external data are loaded. Conversion tools use international unit definitions.

Formula review: October 24, 2026. Read our methodology.