Deck Board Quantity Calculator
Plan straight full-run deck boards, fixed gaps and the final ripped strip using actual board dimensions.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Count parallel strips across the deck width, calculate the last strip and apply an entered order allowance.
Strips=ceil[(width+gap)/(board width+gap)]; last width=deck width−(strips−1)(board width+gap)
Worked example
For 3 m width, 140 mm boards and 5 mm gaps, 21 strips are required. The final strip is 100 mm wide. With 10% allowance, order 24 full-run boards.
Assumptions and input details
Every board is assumed long enough to span the entire entered run; stock lengths, butt joints, diagonal patterns and offcut reuse are not optimized. Widths are actual dimensions, not nominal lumber sizes. Gaps and waste are entered choices and must suit the real material/manufacturer. The calculator does not size joists, beams, fasteners or loads.
References: Trex: board spacing depends on material and installation
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
Choose from 23 length definitions, including explicitly labelled regional measures. Area conversions square the length factor; geometric volumes cube it.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · Japanese traditional units · Mainland China and Hong Kong unit distinctions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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