How to Calculate Linear Feet for Any Project or Material
By The Calcumatix Team Reviewed by Calcumatix Editorial Review 4 min read
Quick Answer
One linear foot equals one foot of length along a single dimension. To calculate linear feet needed for a project, divide the total area by the material width in feet: linear feet = square feet ÷ material width (ft). For 200 sq ft of flooring with 6-inch-wide boards, linear feet = 200 ÷ 0.5 = 400 linear feet. Add 10 to 15 percent for waste on cut materials.
A linear foot is a direct measure of length in one dimension, nothing else. It does not account for width, height, or thickness. This makes it the simplest measurement in construction, but also the most frequently misapplied one: materials are sold by the linear foot but installed to cover area, so projects require converting between the two depending on what is being calculated. This guide explains what a linear foot is, how to calculate it for the most common project types, and how to convert to and from square feet when the material width is known.
What Does a Linear Foot Actually Measure?
A linear foot measures length in one direction only: how long something is, not how wide or tall. A 12-foot piece of crown moulding is 12 linear feet. A 50-foot fence run is 50 linear feet. The width and thickness of the moulding or fence board are irrelevant to the linear foot count. The confusion arises because many building materials come in a fixed width and are sold by the linear foot, which implicitly bundles the width into the pricing. When you buy 6-inch deck boards by the linear foot, the supplier knows the board width; you just need the length.
Linear feet contrast with square feet (area = length × width) and board feet (volume, used for rough lumber). These three measurements serve different purposes, and using the wrong one for a purchase results in either a shortage or significant waste.
| Measurement | Measures | Typical Use |
|---|---|---|
| Linear feet | Length only | Trim, moulding, fencing, piping, framing lumber |
| Square feet | Area (length × width) | Flooring, roofing, paint, tile |
| Board feet | Volume (thickness × width × length) | Rough-sawn lumber, hardwood |
How Do You Calculate Linear Feet for Flooring?
Flooring is sold by the square foot, not the linear foot, so this calculation is about finding how many square feet you need and ordering that way. However, if the flooring comes in strip or plank boards of a fixed width and you want to know the total linear footage to lay, the formula is:
Linear feet = total area (sq ft) ÷ board width (ft)
Flooring Worked Example
Inputs: A room is 20 ft × 15 ft. Flooring planks are 6 inches (0.5 ft) wide.
Step 1: Find the total area Area = 20 × 15 = 300 sq ft
Step 2: Convert to linear feet Linear feet = 300 ÷ 0.5 = 600 linear feet
Step 3: Add waste With 10 percent waste: 600 × 1.10 = 660 linear feet to purchase
Result: Order 660 linear feet of 6-inch planking to cover the room with a 10 percent waste allowance. For rooms with angled cuts, use 15 percent waste instead.
Use the linear feet calculator to quickly convert between area, board width, and total linear feet.
How Do You Calculate Linear Feet for Fencing?
For fencing, calculate the perimeter of the fenced area. The perimeter is the total boundary length and equals the number of linear feet of fence material needed.
Perimeter formula for a rectangular area: Perimeter = 2 × (length + width)
Fencing Worked Example
Inputs: A backyard measures 80 ft × 60 ft. One 80-foot side is the house and needs no fence.
Step 1: Calculate the full perimeter Perimeter = 2 × (80 + 60) = 280 ft
Step 2: Subtract the house side Fence needed = 280 − 80 = 200 linear feet
Step 3: Add for gate and waste A 4-foot gate replaces 4 linear feet of fence panels; add 5 percent material waste: 200 × 1.05 = 210 linear feet of fence panels plus a 4-foot gate
Result: Order 210 linear feet of fence panels and one gate.
How Do You Calculate Linear Feet for Trim and Moulding?
Trim and moulding are sold by the linear foot and installed around the perimeter of rooms, windows, and doors. Measure the length of each run and sum them.
Steps for interior trim:
- Measure each wall length where trim is needed.
- Subtract door and window widths from the wall lengths where trim stops.
- Sum all runs.
- Add 10 percent for waste and mitre-cut losses.
Trim Worked Example
Inputs: A room with four walls: two 12-foot walls and two 10-foot walls. One 36-inch (3 ft) door opening on one 10-foot wall.
Step 1: Sum the wall lengths 12 + 12 + 10 + 10 = 44 linear feet
Step 2: Subtract the door opening 44 − 3 = 41 linear feet of trim needed
Step 3: Add 10 percent waste 41 × 1.10 = 45.1, rounded up to 46 linear feet to purchase
Result: Buy 46 linear feet of trim for this room. Order in the longest available lengths to minimise joints.
How Do You Convert Square Feet to Linear Feet?
To convert square feet to linear feet, you need to know the material width:
Linear feet from square feet: Linear feet = square feet ÷ material width (ft)
Square feet from linear feet: Square feet = linear feet × material width (ft)
Always convert the material width to feet before dividing. Six inches = 0.5 ft; 4 inches = 0.333 ft; 12 inches = 1 ft. You cannot convert between square feet and linear feet without knowing the width, because the calculation needs both dimensions.
Sources
- National Wood Flooring Association: Installation Guidelines, waste factor recommendations for flooring projects.
- This Old House: How to Measure for Trim, step-by-step room measuring guide for moulding and trim.
See all construction measurement tools in the construction calculators hub.
Frequently asked questions
What Is the Difference Between a Linear Foot and a Regular Foot?
They are the same unit of length. "Linear foot" emphasises that only one dimension is being measured, distinguishing it from square feet (two dimensions) and cubic feet (three dimensions). Suppliers use the term to clarify that pricing is by length only, not by area or volume. In everyday measuring, a linear foot is simply 12 inches of length.
How Many Linear Feet Are in a Square Foot?
There is no fixed conversion because it depends on the material width. A square foot is an area; a linear foot is a length. You need the material width to convert: linear feet = square feet ÷ material width in feet. For 6-inch material, 1 sq ft = 2 linear feet. For 12-inch material, 1 sq ft = 1 linear foot.
How Do I Calculate Linear Feet for Lumber?
For framing lumber bought for a specific purpose (studs, joists, rafters), count the number of pieces needed and multiply by the piece length. For a wall with 16 studs each 8 feet long: 16 × 8 = 128 linear feet. For rough-sawn hardwood purchased by board foot, use the board feet formula: (thickness in inches × width in inches × length in feet) ÷ 12. The Linear Feet Calculator handles both unit types.
Should I Add Waste to My Linear Feet Calculation?
Yes. Always add 10 to 15 percent to the calculated total for cut-waste, damaged pieces, and layout adjustments. For diagonal layouts or complex rooms with many angles, use 15 percent. For straight runs with few cuts, 10 percent is sufficient. Buying short and running out mid-project is the most expensive mistake in material ordering; the cost of a few extra linear feet is always less than a return trip to the supplier.