Linear Feet Calculator
Add up linear feet for boards, trim, moldings, fencing and decking — enter piece lengths with quantities, or convert an area in ft² to linear feet from the board width, and get total cost per linear or board foot.
Add Up Linear Feet — Boards, Trim, Fences, Decking and Cost
Linear Feet Formula
Where:
- \(L_i\) — length of piece \(i\), converted to feet (1 ft = 12 in = 0.3048 m)
- \(q_i\) — quantity of identical pieces of that length
Each distinct length gets its own row, and repeats are handled by the quantity, so 12 boards of 8 ft is one row: 8 ft × 12.
When you start from an area instead of piece lengths (decking, flooring, siding), the calculator uses:
Where:
- \(A\) — area to cover in ft²
- \(w\) — actual board width in inches
- \(p\) — waste allowance in %
For pricing, board feet per linear foot equal \(T \times w \div 12\), and the volume of all pieces in board feet is \(\text{LF} \times T \times w \div 12\), where \(T\) is the board thickness in inches.
Linear Feet – Calculation Example
Example: a trim order needs four boards 8 ft long, two boards 10 ft 6 in long, and one piece 96 in long. The lumber is 2× stock (actually 1.5 in thick and 5.5 in wide) priced at $8 per board foot.
\[ 8 \times 4 = 32 \text{ ft}, \qquad \left(10 + \tfrac{6}{12}\right) \times 2 = 21 \text{ ft}, \qquad \tfrac{96}{12} \times 1 = 8 \text{ ft} \]
\[ \text{LF} = 32 + 21 + 8 = 61 \text{ ft} \]
\[ \tfrac{\text{BF}}{\text{ft}} = \frac{1.5 \times 5.5}{12} = 0.6875, \qquad \text{price per LF} = 8 \times 0.6875 = 5.50 \text{ per ft} \]
Result: 61 linear feet total (20.333 yd, 18.59 m). Cost of the pieces: 61 × $5.50 = $335.50, containing 41.94 board feet. Covering a 200 ft² deck with 5.5 in boards plus 10% waste needs 480 linear feet, costing 480 × $5.50 = $2,640.
How to Use the Calculator
- Set Piece rows to show to the number of distinct lengths in your order. Rows below this number are hidden and ignored, so you only enter what you need.
- For each row, enter the length in Piece N length and pick the Unit: ft, ft + in, in, cm or m. If you choose ft + in, an extra inches field appears — e.g. 10 ft + 6 in. Blank rows are skipped.
- Enter Piece N — qty for repeats. A blank quantity counts as 1 piece; a quantity of 0 skips the row.
- For decking, flooring or siding, fill in Area to cover (ft² or m²), the actual Board width, and a Waste / extra allowance of 10–15% for cuts and defects. The calculator converts the area to linear feet and shows the total with waste included.
- To price the job, enter the Price and choose what it is per: linear foot, board foot or piece. Board-foot pricing uses Board thickness together with the board width; per-piece pricing uses the Piece length field to convert the price to a per-foot basis.
The result shows the total length in feet, yards and meters, the linear feet needed for the area, the price per linear foot, the total costs, and the board-foot equivalents. If you also need mixed feet-and-inches arithmetic for site measurements, the Feet and Inches Calculator handles that separately.
What Is a Linear Foot?
A linear foot is simply one foot of length — 12 inches — measured in a straight line along a board, a wall, a fence run or a roll of material. Width and thickness are ignored: a 16 ft board, 16 ft of baseboard and a 16 ft fence section are each 16 linear feet. That is why trim, molding, lumber, pipe, wire, countertop edging and fence rails are quoted per linear foot: only the length matters to the seller.
Linear feet differ from square feet, which measure area (length × width), and from board feet, which measure volume (144 in³ each). A 12 ft board that is 5.5 in wide covers 5.5 ft², and if it is also 1.5 in thick it contains 8.25 board feet — but it is still just 12 linear feet. Choosing the right unit is what avoids the classic ordering mistake of buying "200 feet of decking" and ending up far short of the area you need.
The area mode bridges the two: since one running foot of a board covers \(w/12\) square feet, dividing the area by \(w/12\) — that is, multiplying by 12 and dividing by the width in inches — gives the exact linear footage. The waste allowance then covers offcuts, defects and the small gaps between decking boards.
Interpret the results with the same logic: Total linear feet (pieces) is what you would measure with a tape along every piece end to end; linear feet needed for the area is a purchasing quantity that already includes waste, so round it up to whole boards when ordering.
Assumptions, Limitations and Practical Tips
- Use actual, not nominal, dimensions. A "6-inch" deck board is really 5.5 in wide; 2× lumber is 1.5 in thick. The calculator's defaults reflect these real sizes — nominal numbers will understate the material you need.
- Net face width matters for flooring. For tongue-and-groove boards, the tongue hides inside the groove, so measure the visible face width, not the total board width.
- Add waste deliberately. 10% suits straight runs with few cuts; 15% or more is safer for diagonal decking, curved walls or rooms with many obstacles. Set the allowance to 0 for an exact theoretical figure.
- Board-foot pricing needs thickness and width. If the price is per board foot, the board width from the area section and the thickness field are both used; one linear foot of a 1.5 in × 5.5 in board is 0.6875 BF. To work fully in board feet, see the Board Foot Calculator.
- Units are converted exactly. 1 ft = 12 in = 0.3048 m and 1 m² = 10.7639 ft², so you can mix feet-and-inches lengths with metric pieces in one order. For converting dimensions measured in metric, the cm to Inches Converter is a quick companion.
- Up to 20 distinct lengths. Give each different length its own row rather than averaging — quantities handle repeats, and identical lengths combined into one row keep the math clean.
Frequently Asked Questions
How do I calculate linear feet by hand without the calculator?
Measure each piece's length in feet and add them all up, multiplying each length by how many identical pieces you have. For a mix of 10 boards at 8 ft and 5 boards at 12 ft: \(10 \times 8 + 5 \times 12 = 140\) linear feet. If a measurement is only in inches, divide by 12 first — a 96 in board is 8 ft. Width and thickness never enter the total.
Is a linear foot the same as a regular foot?
Yes — a linear foot is exactly 12 inches or 0.3048 m of straight-line length. The word "linear" only clarifies that you are pricing a long, narrow item by its run, not by area or volume. So 20 linear feet of rope, pipe, baseboard or crown molding is simply 20 feet of that material.
How many board feet are in one linear foot of lumber?
It depends on the cross-section: board feet per linear foot \(= T \times w \div 12\), where \(T\) is thickness and \(w\) is width in inches. One foot of a 2×6 (actually 1.5 in × 5.5 in) is \(1.5 \times 5.5 \div 12 = 0.6875\) BF, while a 4/4 board 6 in wide is 0.5 BF per foot. Multiply by total linear feet to get the full volume.
How do I figure out how many boards to buy from the linear feet total?
Divide the total by the stock length and round up: 61 linear feet of 8 ft boards needs \(61 \div 8 = 7.6\), so buy 8 boards. For a decking or flooring job, do this after the waste allowance is added, and note that leftover offcuts from one row can often start the next, so real usage is sometimes slightly less than this simple division suggests.
Why does my square-foot-to-linear-feet conversion come out short?
The most common cause is using nominal instead of actual board width — a "6-inch" deck board only covers 5.5 in, and tongue-and-groove flooring hides even more of each board in the groove. Measure the true visible face width, then use \(\text{LF} = A \times 12 \div w\). Also add 10–15% waste; without it you are buying an exact theoretical length with zero allowance for cuts and defects.
What's the difference between linear feet, square feet and board feet?
Linear feet measure length only — how long the material runs. Square feet measure area (length × width), used for flooring and decking coverage. Board feet measure volume, with 1 BF \(=\) 144 in³, and are the pricing unit for hardwood and rough lumber. A 12 ft piece of 2×6 is 12 LF, covers 5.5 ft², and holds 8.25 BF.
When do movers or contractors charge by the linear foot?
Movers, freight companies and countertop or trim installers quote per linear foot when the job is essentially a uniform run — for example a trailer space measured along its length, or edging charged by how many feet you need. In these quotes, measure the straight-line distance the material occupies and ignore width or depth. Always check whether the quoted rate includes extra charges such as labor, fasteners or corners.