TOOL 12 / FREE · NO SIGNUP
Deck Board Calculator
Plan parallel deck boards using actual width, gaps and stock length. See the row count and whole stock-board estimate.
Worked example loaded. These are example measurements and product assumptions.
THE METHOD
How to use this estimate
- Length follows the boards; width runs across them. Use actual board width and a product-appropriate gap.
- Rows include gaps between boards, with no added outside-edge gap. The last row may need ripping.
- Stock pieces are counted per row before the final allowance. This conservative model does not reuse offcuts between rows.
rows = ceil((deck width + gap)/(board width + gap)); stock boards = ceil(rows × ceil(deck length/stock length) × allowance factor)
A worked example
The “Load worked example” button uses the same inputs as this example. Explicit unit suffixes keep their meaning in either unit system.
- Deck length along boards
- 4 m
- Deck width across boards
- 3 m
- Actual board width
- 140 mm
- Side-to-side gap
- 5 mm
- Stock board length
- 4 m
- Ordering allowance
- 10
- Deck surface area
- 12 m² / 129.167 ft²
- Straight board courses
- 21
- Stock boards per course
- 1
- Boards before allowance
- 21
- Additional boards after allowance
- 3
- Total ordered stock length
- 96 m / 314.961 ft
Questions, answered
Does this optimize a cutting plan?
No. It counts each row’s stock pieces separately and does not claim the smallest possible purchase.
Does entering a gap make it suitable for my decking?
No. Check the product’s installation instructions. Geometry alone does not approve a spacing or support design.
Sources and product assumptions
These references explain units or product specifications. Your selected product label takes priority; none of these sources endorses this calculator.
Source check: 4 October 2026. Worked examples use stated, editable assumptions.