Lf to Square Feet Calculator: How to Convert

This calculator converts linear feet (lf) to square feet (sq ft) when you know the width in inches. Enter the total length in linear feet and the width, and you get the area in square feet instantly.

Formula

The conversion is straightforward: Square Feet = Linear Feet × (Width in inches ÷ 12).

In symbols: sq ft = lf × (w / 12)

• lf – linear feet (total length in feet)
• w – width in inches
• sq ft – area in square feet

If the width is already in feet, simply multiply linear feet by width in feet: sq ft = lf × w_ft.

Worked Example

Using the calculator defaults: 100 linear feet of material with a width of 12 inches.

1. Convert width to feet: 12 in ÷ 12 = 1 ft
2. Multiply: 100 lf × 1 ft = 100 sq ft

The result is 100.00 square feet.

What Are Linear Feet?

Linear feet (often abbreviated as LF or lf) measure length in a straight line. One linear foot equals 12 inches. It does not account for width or height. For example, a 10-foot-long board is 10 linear feet regardless of whether it is 2 inches wide or 12 inches wide.

Square feet measure area – a two-dimensional space. To get square feet from linear feet, you need a second dimension (width). This is why the conversion requires both length and width.

When to Use This Conversion

You typically need this when buying materials sold by the linear foot but installed over an area. Common examples:

• Lumber and decking – boards are sold by linear foot, but you need to cover a deck area.
• Carpet and flooring – rolls come in set widths (e.g., 12 ft), and you buy by linear foot.
• Fabric – sold by the yard (linear), but you need to cover a surface.
• Fencing – panels or pickets sold by linear foot, but you may need area for paint or stain.

How to Measure Correctly

To get accurate results, measure the length and width carefully. Use a tape measure and record in feet and inches. If you have a mixed measurement like 5 feet 6 inches, convert the inches to a decimal: 6 ÷ 12 = 0.5, so it becomes 5.5 feet. For width, use inches if you are entering it in the calculator above, or convert to feet if using the direct formula.

Always double-check that both dimensions are in the same unit system (imperial or metric). This calculator uses feet and inches; if you have meters, convert to feet first (1 m = 3.28084 ft).

Common Mistakes and Misconceptions

The biggest error is forgetting to convert width to feet. Multiplying linear feet by width in inches gives you square foot-inches, not square feet. For example, 100 lf × 12 in = 1200, which is meaningless unless you divide by 12.

Another misconception: linear feet and square feet are not interchangeable. A 100-square-foot room could be 10 ft × 10 ft, or 20 ft × 5 ft. Knowing only the area does not tell you the linear feet needed for baseboard or trim – you need the perimeter.

Also, be careful with waste. If you are buying material for a project, add 5-10% extra for cuts and mistakes. This calculator gives the exact area, not the amount to purchase.

Limitations and Alternatives

This formula assumes a uniform width along the entire length. If the width varies, you need to calculate each section separately or use an average width (which reduces accuracy). For irregular shapes, divide the area into rectangles, calculate each, and sum them.

If you are working with metric units, the equivalent conversion is: square meters = linear meters × width in meters. You can also use online converters that handle both systems, but the math is the same.

Frequently Asked Questions

How many square feet is 100 linear feet?

It depends on the width. With a width of 12 inches (1 foot), 100 linear feet equals 100 square feet. With a width of 6 inches, it equals 50 square feet (100 × 0.5).

What is the difference between linear feet and square feet?

Linear feet measure length (one dimension). Square feet measure area (two dimensions: length × width). To convert linear feet to square feet, you must know the width.

Can I convert square feet to linear feet?

Yes, but you need the width. Divide square feet by the width in feet. For example, 200 sq ft divided by 2 ft width = 100 linear feet.

How do I convert linear feet to square feet for a room?

For a rectangular room, measure the length and width in feet, then multiply them. That gives square feet directly. Linear feet are not needed unless you are dealing with a material roll width.

Is a linear foot the same as a foot?

Yes, a linear foot is exactly 12 inches, the same as a regular foot. The term “linear” is used to clarify that it is a straight-line measurement, not an area or volume.

What if my width is in centimeters?

Convert centimeters to inches first (1 cm = 0.393701 inches), then use the calculator. Or convert to feet directly (1 cm = 0.0328084 feet) and multiply.

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in lf | Linear Feet | ft | 100 | 0
in w | Width | in | 12 | 0
out sqft | Square Feet | sq ft | lf * w / 12 | 2