To convert square feet to linear feet, divide the area by the usable material width in feet. If the width is in inches, multiply the area by 12 first. You cannot make this conversion from area alone.
Use the linear feet calculator for continuous coverage estimates, an optional material allowance and cost per unit of length.
The square-feet-to-linear-feet formula
A 6-inch-wide strip covers half a square foot per linear foot. Covering 100 square feet therefore needs 200 linear feet. Narrower strips need more total length to cover the same area.
To reverse the calculation, multiply linear feet by usable width in inches and divide by 12. For example, 288 linear feet at a 5.5-inch usable width represents 132 square feet of continuous coverage. If the footage already includes extra material, that area includes it too.
| Usable width | Linear feet, before allowance |
|---|---|
| 3 inches | 400 |
| 4 inches | 300 |
| 5.5 inches | 218.18 |
| 6 inches | 200 |
| 8 inches | 150 |
| 12 inches | 100 |
Example: 120 square feet with a 5.5-inch face
Calculate 120 × 12 ÷ 5.5 = 261.82 linear feet, rounded to two decimal places. If you choose 10% extra material, multiply the unrounded length by 1.10 to get 288 linear feet.
At an example price of $2.50 per linear foot, the allowance-adjusted material cost is 288 × $2.50 = $720. This price is illustrative and excludes tax, delivery and installation.
Dividing 288 by a 12-foot stock length gives 24 pieces by total length. That is a length equivalent, not a checked cutting plan. The lengths of individual runs, joint locations and offcuts can change the number of boards you need.
Use the covering width, not just the product name
Check the actual face width and the installed coverage specified for your material. A nominal width can differ from the measured width. For example, Trex lists a 5.5-inch actual width for its nominal 1 × 6 Lineage decking profile.
Overlap, tongue-and-groove joints and gaps can change coverage. Follow the product’s installation details when choosing the usable width. The calculator does not automatically add a gap, subtract an overlap or account for a pattern.
Working in metric units
For 18 m² covered by a 120 mm usable width, the net length is 18 × 1,000 ÷ 120 = 150 metres. A chosen 8% allowance makes that 162 metres. Keep area, width and price in the units selected in the calculator.
Area, length and lumber volume answer different questions
This method estimates length from continuous surface coverage. It does not decide a structural design or optimize how boards should be cut. For trim around a room, measure the required runs directly instead of entering the room’s floor area.
If lumber is priced by volume, use the board foot calculator. The guide to board feet, linear feet and square feet explains which measurements each unit needs.
Reference and method
The examples rearrange area = width × length. The linked manufacturer specification illustrates nominal versus actual width; it is not a product recommendation. Report a calculation issue.