Quick Answer
Square feet measure area — two dimensions multiplied together (sq ft = length × width). Linear feet measure length — one dimension only. They are not interchangeable, but they connect: linear feet × material width (in feet) = coverage in square feet.
When to Use Square Feet
Use square feet when measuring or pricing a surface:
- Flooring (hardwood, laminate, LVP, tile)
- Paint and primer coverage
- Wallpaper coverage
- Roofing (also expressed in "squares" of 100 sq ft each)
- Real estate property sizes
- HVAC sizing
- Lawn area for seed, sod, fertilizer
When to Use Linear Feet
Use linear feet for anything sold by length:
- Lumber (2×4 studs, deck boards, framing)
- Baseboards and crown molding
- Stair nosing and transition strips
- Fencing material and installation
- Gutters and downspouts
- Pipe and conduit
- Wire and cable
- Cabinet countertop edges
Converting Between the Two
You can convert between square feet and linear feet only when you know the material's width. The formula:
Linear Feet = Square Feet ÷ Material Width (in feet)
Worked example — deck boards:
You need 200 sq ft of deck surface. Your boards are 5.5 in wide (5/4 × 6, actual width). Convert width: 5.5 ÷ 12 = 0.458 ft. Linear feet needed: 200 ÷ 0.458 = 437 linear ft of board.
Worked example — vinyl plank:
You have a 50 linear ft purchase of 7-inch-wide vinyl plank. Width in feet: 7 ÷ 12 = 0.583 ft. Square footage: 50 × 0.583 = 29.2 sq ft.
Common Mistakes
- Pricing confusion. A "$3 per foot" flooring quote almost always means per square foot, but always confirm. Some specialty floors (extra-wide hardwood) are quoted per linear foot to highlight the width premium.
- Carpet conversion. Carpet is sold per square yard. To convert linear feet of carpet roll (12 ft wide) to square yards: linear ft × 12 ÷ 9 = sq yd. So 30 linear ft of broadloom = 40 sq yd = 360 sq ft.
- Lumber estimating. Decking, fencing, and trim all start as square feet (surface area or perimeter), then convert to linear feet using the chosen board width. Skipping the conversion gives wrong material counts.