Formula & method
Rows = ceil((deck width + gap) ÷ (board width + gap)); pieces = rows × ceil(deck length ÷ board length)
Worked example
Rows = ceil((deck width + gap) ÷ (board width + gap)); pieces = rows × ceil(deck length ÷ board length)
Assumptions & limitations
Material estimate only. Verify final quantities, product specifications, plans and local requirements before purchase or construction.