Lumber Calculator
Count the boards a project really takes with this lumber calculator. Pick the cover an area route for a deck and read rows, boards to buy, total board feet and total linear feet in one result. Or pick the count boards route and tally a plain list by size, with board feet and the weight of the load by species. The project comes first here, and the piece count lands before the board foot tally, the way a job actually plans.
What the result numbers mean
Your rows plus waste for your job type, rounded up. This is the count you hand the store.
The boards that span the cover width, each counted at its true width plus the gap. A row count with no gap always reads short.
The buy count times the board feet in each board, on the nominal size. Yards tally and charge on this basis.
The buy count times the board length. Delivery, storage and trim plans read this line.
A plain list tallied by the board foot rule, thickness times width times length over 12, per board and in total.
The count route weighs the tally at your species rate. Pine runs 2.9 pounds per board foot, oak 3.9, walnut 3.5 and cedar 2.3.
How much lumber do I need?
Start from the project, not the board. A deck 16 feet wide with 12 foot boards of 5/4 by 6 decking takes 35 rows at a 1/8 inch gap. With 10 percent waste, buy 39 boards. That is 292.5 board feet and 468 linear feet.
How the math works
Cover an area counts boards for a deck or a floor of boards. Count boards tallies a list you already hold, by size and pieces.
For an area, divide the cover width in inches by the board true width plus the gap. Round up. That is the row count.
Cover in / (Board width + Gap)Decking adds 10 percent. Framing adds 15. Finish work adds 20, because grading and selection eat boards before cuts start.
Decking 10, Framing 15, Finish 20Multiply thickness by width by length in feet, then divide by 12. A 5/4 by 6 board at 12 feet holds 7.5 board feet.
T x W x L / 12The buy count times board feet per board gives the tally. The buy count times board length gives total linear feet.
Pick a species and the tally turns into pounds. The rate is an estimate for load planning, not a scale ticket.
Board feet x Pounds per bfA deck, 16 feet wide and 12 feet long, with 5/4 by 6 boards
Here is the deck from the quick answer, on a breakdown slip, the way the tool builds it.
Read the slip top to bottom. The row pitch is the quiet number in deck math: board width plus gap. Miss the gap and the count reads short by a board on every few rows. The waste line then covers cuts, defects and the one warped board in the pile. The lumber calculator above counts your own deck the same way.
Boards and routes, explained
This lumber calculator knows the true width behind each shelf name, and the board feet in each board. Tap a card to load that board or route in the tool.
The deck standard. True width 5.5 inches, true thickness about 1 inch. Each foot holds 0.625 board feet at the nominal size.
Key measure: 0.625 bf per footTap to load in the calculatorDeck boards, joists and strong frames. True size 1.5 by 5.5 inches. Each foot holds a full 1.00 board foot at the nominal size.
Key measure: 1.00 bf per footTap to load in the calculatorThe framing stud. True size 1.5 by 3.5 inches. Run as deck boards it takes more rows, because each row covers less width.
Key measure: 0.67 bf per footTap to load in the calculatorFence boards stand side by side, so the cover width is the fence length and the board length is the fence height. A 50 foot fence at 6 foot boards loads here.
Key measure: fence length as cover widthTap to load in the calculatorA shed or frame starts as a list of sizes and counts. The count route tallies board feet per board and in total, on the nominal basis.
Key measure: size, length and countTap to load in the calculatorThe same tally weighs apart by species. Ten 2 by 6 boards at 12 feet hold 120 board feet, which is 348 pounds in pine and 468 in oak.
Key measure: pounds per board footTap to load in the calculatorLumber numbers, in one place
| Nominal size | Actual size | BF per foot, nominal | BF in an 8 ft board |
|---|---|---|---|
| 1 x 4 | 0.75 x 3.5 in | 0.33 | 2.67 |
| 1 x 6 | 0.75 x 5.5 in | 0.50 | 4.00 |
| 2 x 4 | 1.5 x 3.5 in | 0.67 | 5.33 |
| 2 x 6 | 1.5 x 5.5 in | 1.00 | 8.00 |
| 2 x 8 | 1.5 x 7.25 in | 1.33 | 10.67 |
| 2 x 10 | 1.5 x 9.25 in | 1.67 | 13.33 |
| 2 x 12 | 1.5 x 11.25 in | 2.00 | 16.00 |
Common mistakes
Yards tally on the nominal name. Figure the tally on actual size and the price talk at the counter goes sideways. This page tallies nominal and labels it.
Boards at true width alone undercount every deck. The gap is small per row and adds a full board on every few rows.
A framing run needs a stud at each end. Wall length over spacing, plus one for the end, is the count. Drop the plus one and the wall ends open.
A diagonal deck lay cuts every board at an angle. At a straight lay waste count the pattern eats the pile before the last row.
How to buy lumber with your count
The result moment is the buying moment. Take the board count and the tally from this lumber calculator to the store or the yard. Two routes cover most lumber buys.
Option A: The big home stores
- Home Depot and Lowes sell by the board. Your boards to buy count is the order number.
- Deck screws and joist hangers are the hardware the deck job needs next. Count them with the boards, not after.
- Sight down each board for bow and twist at the pile. One bad board costs more time than money.
- Long lengths ride poorly in a car. Ask about delivery when the run passes 12 feet.
Option B: The lumber yard
- The yard prices by the board foot. Your tally is the number their quote multiplies.
- For board foot math in full depth, the board foot calculator owns both size bases and the price line.
- Ask about grade. Clear boards cost more per foot and waste less.
- Buy the full list in one trip, so the stack matches in tone and moisture.
For the deck surface as bare area, the square footage calculator owns the flat measure. For the concrete footings under the same deck, the concrete calculator gives yards and bags from one measure.
Questions, answered
Related calculators
Ready to plan your project?
Pick a calculator and get your numbers in seconds.
Find your calculator