Deck Calculator

Estimate deck area and calculate how many deck boards you need including waste. For basic surface measurement, see our Floor Area Calculator.

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Deck Materials Needed: —
Formula:
Area = Length × Width
Adjusted Area = Area × (1 + Waste%)
Board Area = (Width in ft × Length)
Boards Needed = Adjusted Area ÷ Board Area
Example:
20 × 12 = 240 ft²
10% waste → 264 ft²
5.5" × 12 ft board = 5.5 ft²
264 ÷ 5.5 ≈ 48 boards

Frequently Asked Questions

How much waste should I add for decking?

Most decks require 5–15% extra depending on layout and cuts.

Why are boards rounded up?

Deck boards must be purchased whole, so results round up automatically.

Should I include gaps between boards?

Standard deck spacing (1/8"–1/4") slightly reduces coverage but waste percentage typically accounts for this.