ft to square feet calculator

How this ft to square feet calculator works

People often search for a “ft to square feet calculator” when planning flooring, siding, decking, fabric, or rolls of material. The key idea is simple: feet (linear feet) measure length, while square feet measure area. To calculate area, you need both length and width.

This calculator takes a length in feet and multiplies it by a width you enter in either feet or inches. That makes it useful for both room-size calculations and strip-based materials.

Formula for converting feet to square feet

When width is in feet

Square feet = linear feet × width (ft)

When width is in inches

First convert inches to feet: width (ft) = width (in) ÷ 12
Then: Square feet = linear feet × width (ft)

Examples

• 24 linear ft of material that is 18 in wide = 24 × (18/12) = 36 sq ft
• 15 ft by 12 ft room = 15 × 12 = 180 sq ft
• 40 linear ft at 2.5 ft width = 40 × 2.5 = 100 sq ft

Quick reference table

Linear Feet	Width	Square Feet
10 ft	12 in (1 ft)	10 sq ft
10 ft	24 in (2 ft)	20 sq ft
25 ft	18 in (1.5 ft)	37.5 sq ft
30 ft	36 in (3 ft)	90 sq ft

Common use cases

Flooring and carpet

For flooring, you typically use room length × room width directly in feet. If your material is sold by linear foot with a fixed roll width, use this tool with that width.

Deck boards and paneling

Decking and panel projects often involve long strips. In these cases, the linear-foot value is obvious, but the width can vary by product. Always use the actual installed width for better estimates.

Fabric and turf rolls

Roll goods are a perfect match for linear-feet-to-area conversions. Enter your purchased length and the roll width to estimate total coverage in square feet.

Mistakes to avoid

• Trying to convert linear feet to square feet without a width.
• Forgetting to convert inches to feet.
• Using nominal board width instead of actual width.
• Not adding a waste factor for cuts and trim.

Pro tip: add a waste factor

Most projects need extra material. After finding total square footage, add 5% to 15% depending on complexity. For example, 200 sq ft with a 10% waste factor means you should buy about 220 sq ft.

FAQ

Can I convert feet to square feet directly?

Not with one measurement alone. You need a second dimension (width) to calculate area.

Is linear foot the same as square foot?

No. A linear foot is one-dimensional (length). A square foot is two-dimensional (area).

What if I only know one side?

You can only estimate square feet if you assume a width. For a strip exactly 1 foot wide, linear feet and square feet are numerically equal.