What this calculator does
The decking calculator estimates the number of deck boards, fasteners, and total material cost needed to build a deck of a given size.
The formula
The calculator divides your total deck area by the surface area of a single board (its width times its length) to find a base board count, then adds your chosen waste percentage to cover cut-offs and mistakes. Screw quantity is estimated at roughly 3.5 screws per square foot, a common rule of thumb for standard joist spacing.
This is a general estimate for planning purposes. Actual material needs vary with joist spacing, board pattern (straight vs. diagonal), and local waste rates, so always round up and check with your supplier.
Last reviewed August 2026