How to Use This Linear Feet to Square Feet Calculator
Pick the direction you need. On the first tab, type the total length of material in linear feet, then the width of one piece in inches or feet. The calculator returns the net area, the area including your waste allowance, and a suggested order quantity rounded up. On the second tab, enter the area you want to cover and the width of the material, and it tells you how many linear feet to buy, plus how many 8, 10, 12 and 16 ft boards that equals.
Why This Matters
Lumber yards sell decking, fence boards, baseboard and trim by the linear foot, but the job you are planning is usually measured in square feet. A 12 × 16 ft deck is 192 square feet, yet nobody sells deck boards by the square foot. You have to convert in both directions to compare prices, check a quote or avoid a second trip to the store.
The same conversion shows up everywhere. A fence contractor quoting $4.20 per linear foot of 5.5-inch cedar boards is really charging about $9.16 per square foot of coverage. A flooring installer working with 3.5-inch strip oak needs roughly 3.4 linear feet for every square foot of floor, before waste. Fabric, vinyl, gutter guards, roofing underlayment and landscape edging all follow the same pattern.
Getting the conversion wrong is expensive. Under-order by 5% and you wait days for a matching batch, with possible colour variation. Over-order by 30% and you pay for material that sits in the garage. A quick, accurate calculation with a sensible waste factor keeps the project on budget.
How It's Calculated
The math is plain rectangle geometry. A strip of material is a long, narrow rectangle, so its area is its length times its width, with both measured in the same unit. Because length is quoted in feet and width is usually in inches, the width is converted to feet first by dividing by 12.
Net area (sq ft) = length (linear ft) × width (ft)
Area with waste = net area × (1 + waste % ÷ 100)
Linear ft needed = area with waste ÷ width (ft)
Square yards are the area divided by 9, and square meters are the area multiplied by 0.09290304. Order quantities are always rounded up to the next whole square foot or linear foot, never down, so the estimate errs on the side of having enough.
Rule of thumb and limits: this tool uses standard area geometry and the common 5–15% waste guideline for straight-lay projects. No building code sets these numbers. It is a material-estimating aid only, not an engineering, permit or inspection approval. Local codes, span tables and manufacturer instructions vary, so confirm quantities and any structural requirements with your supplier or local building department.
Worked Example
You are decking a small platform with 5.5-inch wide boards (the actual width of a 5/4×6 deck board) and have priced 120 linear feet. Allow 10% waste.
- Width in feet: 5.5 ÷ 12 = 0.4583 ft
- Net area: 120 × 0.4583 = 55.00 sq ft
- Waste at 10%: 55.00 × 0.10 = 5.50 sq ft
- Area with waste: 55.00 + 5.50 = 60.50 sq ft, so order at least 61 sq ft worth
- In other units: 60.50 ÷ 9 = 6.72 sq yd, and 60.50 × 0.0929 = 5.62 sq m
Going the other way, to cover 200 sq ft with the same boards plus 10% waste you need 220 ÷ 0.4583 = 480 linear feet. That is 60 boards at 8 ft, 48 at 10 ft, 40 at 12 ft or 30 at 16 ft.
Tips & Common Mistakes
- Use actual width, not nominal. A "1×6" or "2×6" is about 5.5 inches wide, a 2×4 is 3.5 inches, and a 1×8 is 7.25 inches. Using the nominal size overstates your coverage.
- Account for gaps. Deck boards are often spaced 1/8 to 1/4 inch apart. For tighter accuracy, add the gap to the board width, so a 5.5 in board with a 1/8 in gap covers 5.625 in.
- Match waste to the layout. Straight runs often need 5–10%, diagonal or herringbone patterns 15% or more, and rooms with many cuts or defective stock may need extra. Round up, never down.
- Do not mix units. The most common error is multiplying feet by inches. If the width is 12 inches or more, double-check that you chose the right unit.
- Think about board length. Buying 16 ft boards for a 10 ft run wastes 6 ft per piece. Choose lengths that divide well into your runs.
Frequently Asked Questions
How do you convert linear feet to square feet?
Multiply the length in linear feet by the width in feet. If the width is in inches, divide it by 12 first. For example, 100 linear feet of 6-inch wide material is 100 × 0.5 = 50 square feet.
How many linear feet are in a square foot?
It depends on the width. Divide 12 by the width in inches. A 3.5-inch board gives about 3.43 linear feet per square foot, a 5.5-inch board gives about 2.18, and a 12-inch board gives exactly 1.
Can you convert linear feet to square feet without a width?
No. Linear feet measure length only, and square feet measure area, so you need a second dimension. Without a width, any answer would be a guess.
How much waste should I add for flooring or decking?
A common starting point is 10% for straight-lay installations and 15% for diagonal or complex layouts. Add more if the room has many corners or if you want spare boards for future repairs. Always round the final quantity up.
How do I convert square feet to linear feet?
Divide the area in square feet by the width in feet. To cover 150 sq ft with 7.25-inch boards (0.604 ft), you need about 248.3 linear feet before waste. Use the second tab above to include waste and round up automatically.
Is a linear foot the same as a board foot?
No. A linear foot is one foot of length regardless of thickness or width. A board foot is a volume of 144 cubic inches, usually 1 inch thick by 12 inches wide by 12 inches long. Hardwood is often priced by the board foot, while dimensional lumber and trim are priced by the linear foot.