Deck Square Footage Calculator
Every other deck calculator starts with area. Measure one rectangle, circle or triangle, multiply for repeated sections, and you have the square footage everything else runs on.
Result
- Total area192sq ft
- Area (metric)17.84m²
- Area (sq yd)21.33sq yd
How it works
area = length × width
- Rectangle = 16 ft × 12 ft = 192 sq ft
How the deck square footage calculator works
Area is length times width for a rectangle, πr² for a circle and half the base times height for a triangle. Nothing more.
Real decks are usually several rectangles bolted together. Calculate each section separately and add them — that's why the calculator includes a repeat multiplier and why you can run it per section.
Round your measurements to the nearest inch before converting to feet; measuring to the quarter inch adds precision the lumber yard can't sell you.
Formula
rectangle = length × width | circle = π × (d ÷ 2)² | triangle = (base × height) ÷ 2
Worked example: L-shaped deck as two rectangles
- Section A = 16 × 12 = 192 sq ft
- Section B = 8 × 6 = 48 sq ft
- Total = 192 + 48 = 240 sq ft
- In metric = 240 × 0.0929 = 22.3 m²
- Feed 240 sq ft into the boards or cost calculator
Common deck sizes
| Dimensions | Square feet | Square metres | Boards (5.5" × 12 ft, +10%) |
|---|---|---|---|
| 8 × 10 ft | 80 | 7.4 | 16 |
| 10 × 12 ft | 120 | 11.1 | 24 |
| 12 × 12 ft | 144 | 13.4 | 29 |
| 12 × 16 ft | 192 | 17.8 | 38 |
| 16 × 20 ft | 320 | 29.7 | 63 |
Board counts from the deck boards calculator with a 10% waste allowance.
Frequently asked questions
How do I measure square footage of an irregular deck?
Split it into rectangles, triangles and circles you can measure. Calculate each shape with the calculator, then add the results. An L-shape is two rectangles; a curved end is a rectangle plus half a circle.
How many square feet is a 12×16 deck?
192 square feet, which is 17.8 square metres. That area needs about 38 boards (5.5" × 12 ft with 10% waste) or roughly $1,560 in DIY pressure-treated materials.
How many square feet do I need for a deck with furniture?
Plan for a dining table plus circulation at about 60 sq ft, and each lounge chair with its side table at about 30 sq ft. A typical outdoor dining set plus grill lands around 150–200 sq ft.
How do I convert square feet to linear feet of boards?
Divide the area by each board's coverage: face width plus gap, times length, all over 12. The square-feet-to-linear-feet converter does it directly — 200 sq ft of 5.5" boards is about 422 linear feet.