Decking Board Calculator
Estimate decking board quantity for a rectangular deck.
Calculation example
Inputs: Deck Length (ft): 20 ft, Deck Width (ft): 12 ft, Board Width (in): 6 in, Gap (in): 0.125 in, Board Length (ft): 12 ft, Waste %: 0 %
Result: 48 boards
A 12 ft by 20 ft deck using 6 inch boards, a 0.125 inch gap and 12 ft boards needs 48 boards before waste in this simplified row calculation.
Formula
Boards needed = board rows × boards per row, adjusted by the selected waste percentage.
How to use this calculator
Estimate the number of board rows from deck width and board width plus gap, then divide the deck length by board length and add waste.
Before you calculate
Measure the project dimensions as accurately as practical and keep all measurements in compatible units. For material products, use the coverage, yield, density, or package size stated by the manufacturer or supplier rather than a generic assumption.
Choose the waste allowance based on the project shape, installation method, cutting requirements, and material characteristics. A simple rectangular estimate may need adjustment for openings, corners, slopes, joints, patterns, compaction, or other site conditions.
Understanding the result
The calculator provides a planning estimate based on the inputs shown above. It is not a substitute for project drawings, structural design, manufacturer instructions, or local requirements. Before ordering, compare the calculated quantity with the supplier's package sizes and ordering units.
Tips
- Joins, overhangs, picture framing and board lengths can change the actual quantity.
Frequently asked questions
How are decking boards estimated?
Board rows are estimated from deck width and board plus gap, then boards per row from deck length and board length.
Does it include waste?
Yes. The selected waste percentage is applied.
Related calculators
Use compatible units and verify estimates against project specifications, local requirements and manufacturer instructions.