Linear feet are just feet
There is no separate 'linear foot' unit. The word exists to remove ambiguity in trades where the same material can be sold by length, by area or by volume.
Fencing, trim, gutter, conduit, cable and pipe are priced per linear foot. Flooring and roofing are priced per square foot. Framing lumber is often priced per board foot, which is a volume.
For conversion purposes, a linear foot is a foot. Divide by 5,280 and you have miles.
| Unit | What it measures |
|---|---|
| Linear foot | Length along one line — 1 ft |
| Square foot | Area — 1 ft × 1 ft |
| Board foot | Volume — 144 cubic inches (1 ft × 1 ft × 1 in) |
| Cubic foot | Volume — 1 ft × 1 ft × 1 ft |
Where the mile conversion actually matters
On most jobs it does not — nobody quotes a kitchen in miles. It matters on infrastructure: utility runs, highway barrier, rail, pipeline, perimeter fencing on large sites.
A quote for 26,400 linear feet of guardrail is 5 miles of guardrail. Stating it in miles makes the scale legible to anyone reading the bid, and makes an order-of-magnitude error obvious.
It also matters for material logistics. Cable is delivered on reels rated in feet, but routes are planned in miles, and reconciling the two is where shortfalls appear.
Going the other way, miles to feet does the reverse conversion. If you want a figure already worked out, conversion chart lists the common ones, and about & methodology documents every constant used here and where it comes from.
5,280 linear feet = 1 mile. 26,400 linear feet = 5 miles. Restating a large quantity in miles is a cheap sanity check.
The board-foot trap
A board foot is a volume: 144 cubic inches, equivalent to a piece one foot by one foot by one inch. It has no direct conversion to linear feet without knowing the lumber's cross-section.
A 2×4 is nominally 2 inches by 4 inches but actually 1.5 by 3.5, giving 5.25 square inches of cross-section. One linear foot of 2×4 is therefore 5.25 × 12 ÷ 144 = 0.4375 board feet.
So 1,000 linear feet of 2×4 is 437.5 board feet. Quoting one figure when the supplier expects the other is a routine and costly error.
- Linear feet → miles: divide by 5,280.
- Linear feet → board feet: needs the cross-section.
- 1 linear ft of 2×4 ≈ 0.4375 board feet.
- Square feet → square miles: divide by 27,878,400, not 5,280.
Board feet: the unit that looks linear but is not
There is one unit in timber that regularly catches people new to construction. A board foot is not a length — it is a volume: 144 cubic inches, or a board 12 inches wide, 12 inches long and 1 inch thick.
So 10 linear feet of 2×6 is not 10 board feet. A 2×6 actually measures 1.5 × 5.5 inches, so 10 feet of it is about 5.5 board feet.
The rule is: linear feet for the length you are buying, board feet for the quantity of wood you are getting. The two are not interchangeable, and mixing them in a quote changes the price substantially.
Measuring length over uneven ground
The length on a plan is horizontal distance; the length on the ground follows the terrain. On steep ground the two differ noticeably.
The arithmetic is Pythagorean. Over 1,000 feet of horizontal distance with 200 feet of drop, the actual ground length is about 1,020 feet — two per cent more.
At a 30 per cent slope the excess is about four per cent. That sounds small until you multiply it by a mile: 5,280 feet on paper becomes 5,490 feet of actual cable or fence.
So in hilly terrain the standard 5 per cent allowance is not enough. Measure the actual profile where you can, or treat 10 per cent as the minimum.
Voltage drop: where length really bites
In electrical work, length is not just a cost line — it is a design constraint. Every foot of conductor has resistance, and that resistance becomes voltage lost at the far end of the run.
The usual limit is 3 per cent for a branch circuit and 5 per cent overall. On 12-gauge cable at 20 amps, 3 per cent arrives at roughly 100 feet — about 0.019 miles.
So long runs need thicker cable. A mile-long run at 240 volts is impossible in ordinary gauge; you need higher voltage or a much larger conductor. That is where 5,280 feet stops being a number in a quote and becomes an engineering problem.
Related conversions: ft/s to mph for speed, sq ft to sq miles for land area, and feet to mil for the unit people most often confuse with the mile.
The allowance people forget
The theoretical length is never the length you have to buy. Cable sags, fencing follows the contour of the ground, and pipe has bends in it.
An allowance of 5 to 10 per cent is normal on a straight run, more in hilly terrain. A one-mile run may need 5,600 feet of material rather than 5,280.
This is one reason it matters to divide exactly and not round early. If you round up and then add an allowance, you have paid for the same margin twice — and on a project measured in miles of cable, that is a real number rather than a rounding detail.
Key takeaways
- A linear foot is a foot — divide by 5,280 for miles.
- 'Linear' only distinguishes length from area and volume pricing.
- Board feet are a volume and need the lumber cross-section to convert.
- Restating large linear-foot quantities in miles catches order-of-magnitude errors.
Try it yourself
Ft to Miles Calculator
Convert feet to miles and back, live as you type.