How to calculate linear feet
To calculate linear feet, as this linear foot calculator does, add the lengths of all the pieces in feet. A linear foot (also called a lineal foot or running foot) measures length only, so a 1x4 and a 2x12 of the same length have the same linear feet. Mixed lengths are easiest in a list:
- 10 pieces at 8 ft = 80 ft
- 4 pieces at 2 ft 6 in = 10 ft
- Total = 90 linear feet
Type lengths as they read on the tape: 2' 6", 30" or 2.5. To add or subtract odd lengths first, use the feet and inches calculator.
Linear feet to square feet and board feet
Linear feet become square feet once you know the board's width, and board feet once you also know its thickness:
| To get | Formula | Example: 100 LF of 1x6 |
|---|---|---|
| Square feet of face | LF × width (in) ÷ 12 | 100 × 5.5 ÷ 12 = 45.8 sq ft (actual width) |
| Board feet | LF × thickness × width ÷ 12 | 100 × 1 × 6 ÷ 12 = 50 bd ft (nominal) |
| Metres | LF × 0.3048 | 30.48 m |
Use the actual face width for coverage (a 1x6 is 5-1/2 in wide[1]) and the nominal size for board feet, as lumber is tallied. The board foot calculator handles mixed sizes.
Linear feet to cover an area
Boards laid side by side cover the area divided by the width each board shows, so the length needed is area × 12 ÷ face width in inches. Add the gap for decking (open gaps add to each board's share) or subtract the lap for siding. Deck boards are fastened to every joist they cross, and the IRC sets how far apart those joists may be for each decking thickness[2]. For decks, the composite deck calculator lays out rows and stock lengths, and the deck calculator adds the frame.
Buying by the linear foot
Trim, moulding, fascia, deck boards and some hardwood are priced per linear foot. Convert your list to pieces of the stock length you can buy, then check that the offcuts work: a 10 ft run cut from 8 ft stock wastes 6 ft. DCA 6 notes that each deck board should bear on at least three joists, which rules out very short offcuts on decks[3].
Frequently asked questions
What is a linear foot calculator?
A tool that adds up lengths in feet, whatever the width of the boards, and converts the total to square feet or board feet once you give it a width and thickness.
How do you calculate linear feet?
Add the length of every piece in feet. Pieces × length, summed over each size.
How many linear feet are in a square foot?
It depends on width. Boards 12 in wide cover 1 sq ft per linear foot; boards 6 in wide need 2 linear feet per square foot.
Is a linear foot the same as a foot?
Yes. A linear foot is 12 inches of length; the word only signals that width and thickness are ignored.
How do I convert linear feet to board feet?
Multiply linear feet by thickness and width in inches and divide by 12. 100 LF of 2x4 is 100 × 2 × 4 ÷ 12 = 66.7 board feet.
How do you convert board feet to linear feet?
Linear feet = board feet × 12 ÷ (thickness × width in inches). 10 board feet of 1x6 is 10 × 12 ÷ 6 = 20 linear feet.