Linear Feet Calculator

What a linear foot measures#

A linear foot (also called a lineal foot) is one foot of length: exactly 12 inches. It is a one-dimensional measurement. Width and thickness do not change the number of linear feet, although they matter when converting area or board-foot volume.

For example, one 8-foot board, one 8-foot pipe and one 8-foot strip of molding are each 8 linear feet long. They may have different widths, thicknesses and uses, but their measured length is the same.

The calculator keeps those measurement types separate:

• Use Pieces → length for equal boards, pipes, trim pieces or rolls.
• Use Add runs for several fence sides, walls, baseboard runs or measured segments.
• Use Perimeter for a rectangular room, building or fence layout.
• Use Area ↔ length only when the material's installed coverage width is known.
• Use Length → pieces when material is sold in fixed stock lengths.
• Use Board feet when converting lumber volume and length with a known thickness and width.
• Use Cost per foot to calculate a total or derive the price per linear unit from a quote.

How to calculate linear feet#

For separate measured runs, add their lengths:

For repeated pieces of the same length:

Ten pieces that are each 8 ft long equal 80 linear ft. If the project needs a 10% extra allowance, the planning length becomes 88 linear ft. Waste is applied once to the combined base length; it is not repeatedly compounded on every line.

Keep all measurements in one unit before adding them. This calculator converts between US Customary and metric values while preserving the physical length. The conversion uses the exact international definition of 1 inch = 25.4 millimeters, so 1 foot = 0.3048 meter exactly.

Fence, room and baseboard perimeter#

For a rectangular layout, the gross perimeter is:

A 20 × 12 ft room has a 64 ft perimeter. If a 3 ft doorway receives no baseboard, the net baseboard run is 61 linear ft before waste. The same geometry can estimate a simple rectangular fence, but subtract gates or unfenced sides.

Irregular layouts should use Add runs. Measure each actual side instead of forcing the project into a rectangle. A fence linear feet calculation does not determine post spacing, panel compatibility, corners, slopes, hardware or installation method; those are separate design and purchasing decisions.

Convert square feet to linear feet correctly#

Square feet and linear feet measure different things. There is no universal feet-to-linear-feet conversion because ordinary feet and linear feet already represent the same length. There is also no universal square-feet-to-linear-feet conversion without a coverage width.

When the installed coverage width is known:

The units must be compatible. A 120 ft² area covered by material with a 6 in installed width uses a width of 0.5 ft:

Use the effective installed width. Tongue-and-groove boards, lapped siding and overlapping sheet products can cover less than their full physical width. Manufacturer instructions or the approved project specification should control that value.

Convert required length to stock pieces#

When boards, rails, pipe or trim are sold in fixed lengths, the basic purchasing count is:

If 100 linear ft is required and stock is sold in 8 ft pieces, the basic result is 13 pieces, providing 104 ft. With a 10% allowance, 110 ft is required and the basic result rises to 14 pieces, providing 112 ft.

This is a quantity check, not a cutting-stock optimizer. Suppose a project needs many segments just over half a stock length; the unused portion of one piece may not fit another required segment. Check a real cut list, available stock lengths, defects, pattern matching, joints and minimum splice rules before ordering.

Board feet to linear feet#

A board foot is a volume equal to 144 cubic inches. Linear feet measure only length, so a board-foot conversion also needs thickness and width.

Using dimensions in inches and length in feet, the familiar relationship is:

For example, 100 board ft at a 2 × 8 in calculation basis equals:

Nominal and actual lumber dimensions are not the same thing. Pricing conventions also vary. Enter the thickness and width used by the supplier, estimate or inventory record you are converting. The calculator deliberately does not guess whether a “2 × 8” should be treated as nominal 2 × 8 in or an actual dressed size such as 1.5 × 7.25 in.

Calculate cost per linear foot#

To estimate a total from a known rate:

To derive the rate in a quote:

One hundred linear ft at USD 2.50 per ft equals USD 250. If a supplier instead quotes USD 375 for 150 ft, the implied rate is USD 2.50 per ft.

Currency selection changes the label only. It does not look up exchange rates, regional prices or sales-tax rules. The optional fixed cost and tax fields are transparent scenario inputs, not market estimates.

Waste, ordering and rounding#

Waste is not part of the definition of linear footage. It is a purchasing allowance layered on top of the measured quantity. Appropriate waste depends on cuts, defects, laps, matching, corners, experience and return policies. The Quick result therefore starts at 0% instead of inventing a universal recommendation.

The optional purchase-rounding field rounds the waste-adjusted length up to the next increment you enter. It is useful when a supplier sells only a stated length increment, but it does not replace the dedicated whole-stock-piece calculation.

The result breakdown keeps three quantities distinct:

1. Base length from the selected geometry or conversion.
2. Required length after the entered waste percentage.
3. Planning or purchase length after optional rounding.

That separation makes it possible to audit where extra material came from.

Common mistakes to avoid#

1. Multiplying length by width and still calling the answer linear feet; that product is area.
2. Converting square feet to linear feet without an installed coverage width.
3. Adding mixed feet, inches and meters before converting them to a common unit.
4. Applying waste to each intermediate number and then applying it again to the total.
5. Treating a rounded stock-piece count as a cut-optimization plan.
6. Converting board feet without specifying thickness and width.
7. Mixing nominal lumber dimensions with actual dimensions in the same estimate.
8. Assuming a currency label supplies local prices or performs exchange-rate conversion.

Assumptions, limitations and sources#

This calculator is for measurement and preliminary purchasing estimates. It does not inspect a site, create a cut list, select a material, determine code compliance or replace project drawings, manufacturer instructions or a supplier takeoff. Verify field measurements and the installed coverage dimension. Complex curves, miters, laps, pattern matching, unusable offcuts and structural requirements need project-specific treatment.

The formula is shown, assumptions are editable, limitations are disclosed and the engine is tested against known cases. No organization below endorses Efficienco.

• NIST: SI Units — Length — SI length and the exact international inch-to-millimeter relationship used for conversions.
• NIST Special Publication 811 — authoritative guidance for using SI units and conversion practices.
• USDA Forest Products Laboratory: Wood Handbook (2021) — reference context for commercial lumber and wood-product measurement.

Method and sources reviewed September 10, 2026 · Engine linear-1.0.0 · Prices and project allowances are entered by the user.