How do I calculate deck materials?

Calculate deck area (length × width), divide by board coverage. Standard: 5.5" boards cover 0.46 sq ft each. Add joists every 16" on center, posts every 6-8ft. Add 10% waste for all materials.

What size deck boards should I use?

2×6 (5.5" wide): most common, good balance. 2×4 (3.5"): smaller decks, lower cost. 5/4×6 (5.5"): lighter weight, composite decking. Longer boards (12-16ft) mean fewer butt joints.

How much does deck material cost?

Pressure-treated: $2-4/sq ft. Composite: $4-8/sq ft. Cedar/redwood: $6-10/sq ft. Hardware, joists, posts add $3-5/sq ft. Total DIY material cost: $15-25/sq ft.

What else do I need besides boards?

Joists (support every 16"), posts (every 6-8ft), beams, ledger board, joist hangers, deck screws (3" stainless), post anchors, concrete for footings, railing system.

How far apart should deck joists be?

16 inches on center for 2× boards, 12 inches for 5/4 boards. Closer spacing for composite decking (check manufacturer specs). Proper joist spacing prevents bouncing and sagging.

Deck Calculator

Calculate deck boards, joists, and materials needed

Deck Calculator

Calculate decking materials needed for your project. Get board counts, joist requirements, post numbers, and cost estimates.

Deck Dimensions

Deck Length *

Length of the deck

Deck Width *

Width of the deck

Board Specifications

Board Length *

Typical: 8ft, 10ft, 12ft, or 16ft

Board Width *

Common: 5.5 inches (2×6) or 3.5 inches (2×4)

Spacing Gap *

1/4 inch standard for drainage and expansion

Deck Building Guidelines

Standard deck boards are 2×6 (actual 5.5 inches wide) or 2×4 (3.5 inches). Use 1/4 inch spacing between boards for drainage and wood expansion. Joists should be spaced 16 inches on-center for structural integrity.

Posts are typically 4×4 pressure-treated lumber, spaced 6-8 feet apart for proper support. Use 2.5-inch coated deck screws, installing 2 screws per joist crossing. Add 10% extra materials for cuts, waste, and end trimming.

Frequently Asked Questions

Everything you need to know about this tool