Deck Material Calculator
Turn rectangular deck sections into a material purchase plan. Choose board direction, stock length, gaps and a picture frame, then inspect the cuts allocated to each stock board. Optional stair treads add decking cuts without claiming a structural stair design.
Your result
How the calculation works
Board courses = round up((deck width + gap)/(board width + gap)). Geometric joists = round up(board run / entered spacing) + 1. Cuts are packed longest-first into stock lengths with saw kerf. Purchase boards = round up(packed boards × allowance).
Worked example
A 4 m × 3 m section, boards running 4 m, 0.14 m boards, 0.005 m gaps and no picture frame needs 21 field cuts of 4 m. With 4 m stock, each uses one board; 10% extra gives 24 boards. At 0.4 m spacing there are 11 geometric joists.
Assumptions and limitations
One stock length, rectangular sections and no spliced field boards. Picture frames use two full-length edges and two inset edges. Cuts longer than stock are rejected; split a section only where a properly designed joint exists. Kerf is conservatively reserved at every cut.
Joist counts and entered spacing are quantity assumptions, not span tables or structural approval. Beams, posts, footings, blocking, hangers, railings and stair stringers are excluded. Have the assembly designed for local loads and requirements before ordering.
Sources and editorial responsibility
Maintained by Renvoro Pty Ltd. Sources inform the methods and assumptions shown here; outputs have the limitations described on this page.
Method reviewed 2026-10-11. Calculation standards · Report an issue