Decking Calculator

Estimate board rows, linear footage, purchase counts by length, and fastener quantities from deck footprint, board width, gap, and joist spacing.

Configuration

Deck Shape

Main Width (ft)

Main Depth (ft)

Boards run across the Width.

Board Type

Actual Board Width (inches)

Gap Spacing

Joist Spacing (On Center)

Fastener System

Waste Factor (For cuts & mistakes)

Deck Boards

Joists (Visible)

Total Linear Feet

0 ft

Includes waste factor

Decking Rows

Across the 12' depth

Board Purchasing Guide
                        If buying 8' boards: 0
                    
                        If buying 12' boards: 0
                    
                        If buying 16' boards: 0
                    
                        If buying 20' boards: 0

Fastener Estimate
                        Face Screws Needed:
                        0
                    
                        Includes 5% extra.

Ordering Decking That Fits the Frame

Decking quantity is not just area divided by board width. Gaps between boards for drainage and swelling, how boards run relative to the joists, and which stock lengths your supplier carries all change the order. This calculator converts deck dimensions into rows and linear feet for rectangle, L-shape, and U-shape layouts, shows how many boards to buy at common lengths after a waste factor, and generates a printable cut list with end-cut diagrams.

How to use this calculator

Pick a deck shape. For L and U shapes, enter the wing dimensions in addition to the main section.
Set board width, gap, joist spacing, fastener type, and waste factor.
Review the visual (joists are visible underneath the semi-transparent boards), the board purchasing guide, and the cut list. Print the cut list for the job site.

Joist spacing, gap, and waste

Most residential decks use 16″ OC joists; 12″ OC stiffens thinner or groove-and-clip composites, while 24″ OC is only for products rated for it. Gap depends on material—pressure-treated softwood often starts around ⅛″ when wet-installed; many composites specify a temperature-based gap from the manufacturer. Waste at 10% covers end cuts and bad boards; picture-frame borders, diagonal decks, and heavy cull rates push you toward 15%. Prefer board lengths that land joints on joists and stagger butts so you are not stacking seams on one joist line.

FAQ

Does this include framing lumber?

No. It estimates decking surface boards and fasteners only. Joists, beams, and posts need a separate framing takeoff.

Should I buy all one length?

Mixing lengths can reduce waste if your deck dimension divides cleanly, but one length simplifies staging. Check which lengths your yard stocks in that species or composite line.

Why does joist spacing affect fasteners?

Face screws are typically two per joist crossing; closer joists mean more crossings per board and a higher screw count.

Is the waste factor applied to fasteners too?

Board waste uses your selected factor; the fastener estimate adds a smaller buffer (about 5%) for drops and stripped screws.

Where this fits in the workflow

Board Foot Calculator Cost the decking and framing lumber.
Screw & Drill Bit Chart Deck screw and pilot sizing for the species you picked.
Wood Species Database Rot resistance and hardness for an outdoor surface.

Read the longer write-up

Deck Takeoff: Gaps, Joists, Waste, and L/U Cut Lists Board count for a deck depends on gap spacing, joist layout, and shape. How to estimate materials for rectangle, L-shape, and U-shape decks including a printable cut list.

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