Deck Calculator

Measure your rectangular deck surface, choose board direction, enter the actual board width and length plus gap between boards, add a waste allowance, and press Calculate. The calculator determines row count (in Deck dimensions mode), total board length required, exact boards before waste, and boards to buy rounded up to whole boards.

Use the actual face width—the dimension after planing or manufacturing—not the nominal lumber name. A nominal 6-inch board often measures about 5.5 inches. Enter the width from your product specification. Using nominal size overestimates coverage and underestimates the number of boards needed.

Gap is added to board width to determine coverage width per row. A larger gap means fewer rows fit across the deck and reduces area-based coverage per board. Enter the gap you plan to use and confirm it matches your product and manufacturer instructions.

Board direction determines which deck dimension boards run along (board run length) and which dimension sets the number of rows (cross-deck width). Swapping direction changes row count and total board length required even when deck area stays the same.

Yes, use Known deck area mode and enter total square footage or square meters. The calculator divides deck area by nominal coverage area per board. This is an area-based estimate—it does not account for deck proportions, row geometry, or joint placement, so it is less precise for layout planning than Deck dimensions mode.

Waste depends on deck geometry, board direction, stagger pattern, cuts, damaged boards, and installer experience. A 10% allowance is a common planning starting point, but complex layouts often need more. Enter the percentage that fits your project—the calculator does not prescribe one universal value.

Decking boards are purchased as whole units. After waste is applied to the exact board count, the calculator rounds up with Math.ceil. If the exact count with waste is already a whole number, no extra board is added. Partial boards cannot be purchased.

Sometimes, but not always. Offcut reuse depends on deck geometry, board direction, stagger requirements, joint placement, and whether leftover pieces meet length and quality requirements. This calculator does not optimize cut patterns or guarantee that offcuts can be reused.

No. The estimate multiplies your optional price per board by boards to buy only. It does not include joists, beams, posts, concrete, fasteners, clips, screws, railing, stairs, fascia, framing, flashing, tools, surface preparation, delivery, taxes, or labor.