Free lumber calculator
Turn a pile of measurements into a shopping list: enter the total linear feet of lumber your project needs, the board length you'll buy, and the price per board, and this calculator works out how many boards to put in your cart, the board feet, and the cost — boards, board feet, and dollars all updated live, as you type.
On this page14 sections
2×6 nominal — actual surfaced size 1.5" × 5.5".
| Item | Quantity | Est. cost |
|---|---|---|
| 2×6 boards | 22 × 12 ft | $308.00 |
| Per board | $14.00 | — |
Cost = boards × price per board. Board feet use the nominal size (2×6 → 2 × 6), the lumber-yard convention; the actual surfaced size is 1.5" × 5.5". Prices vary by species, grade and market — confirm at the yard.
Board feet use nominal sizes; prices vary by species, grade and supplier. How accurate is this?
Results are estimates. Consult a professional.
How the lumber calculator works
Lumber is bought as boards of a fixed length — 8, 10, 12, 16 feet — but a project is measured in the total run of material it needs. The lumber calculator bridges the two. You tell it how many linear feet of a given size you need and what length of board you plan to buy; it divides one by the other, rounds up to whole boards because you cannot buy half a board, and adds a waste margin for cuts and defects. From the same inputs it tallies board feet (the volume unit yards sell rough lumber in) and multiplies the board count by your price to estimate the bill.
What the result means
The headline is the board count — the number of full-length pieces to put in your cart, waste already included. The board-feet figure is what a yard selling rough hardwood or quoting by volume will price against. The cost is the board count times your per-board price. Buy in whole boards: even if your run divides evenly, defects and end-trimming mean the waste margin keeps you from a second trip to the yard.
Nominal vs. actual lumber sizes
A 2×4 is not 2 inches by 4 inches. The number on the bin — the nominal size — is the rough dimension before the board is dried and planed smooth. Drying and surfacing shave off the difference, so the board you carry home is smaller. Length is the exception: a 12-foot board is a full 12 feet (sometimes a hair over for trimming). Only thickness and width shrink.
| Nominal size | Actual size | Board feet per linear foot |
|---|---|---|
| 1×4 | 0.75" × 3.5" | 0.33 |
| 1×6 | 0.75" × 5.5" | 0.50 |
| 2×2 | 1.5" × 1.5" | 0.33 |
| 2×4 | 1.5" × 3.5" | 0.67 |
| 2×6 | 1.5" × 5.5" | 1.00 |
| 2×8 | 1.5" × 7.25" | 1.33 |
| 2×10 | 1.5" × 9.25" | 1.67 |
| 2×12 | 1.5" × 11.25" | 2.00 |
| 4×4 | 3.5" × 3.5" | 1.33 |
Actual (surfaced-dry) sizes follow the Lowe's / ALSC softwood lumber chart. Board feet per linear foot use the nominal size ÷ 12 — the lumber-yard convention — so a 2×6 is exactly 1 board foot per running foot.
A worked example using the lumber calculator
Maria is building a ground-level deck frame. After laying out the joists, rim and blocking she totals 240 linear feet of 2×6. Her yard stocks 12-foot boards at $14 each, and she wants a 10% waste margin for cuts and the odd cupped board.
Step 1 — Add the waste margin to the run
240 linear feet × 1.10 = 264 linear feet of 2×6 to buy, allowing for offcuts and defects.
Step 2 — Convert the run into whole boards
264 ÷ 12 ft per board = 22 boards exactly, so she needs 22 boards. (Without waste it would be 240 ÷ 12 = 20 boards — the margin adds two.)
Step 3 — Tally the board feet
A 2×6 is 1 board foot per linear foot, so the bare project is 240 board feet; the 22 boards she buys total 22 × 12 = 264 board feet.
Step 4 — Estimate the cost
22 boards × $14 = $308 for the 2×6 framing, before tax and any other sizes the deck needs.
How many boards do I need?
If you want a ballpark before you price anything, this table shows how many whole boards a run takes at common board lengths — bare count, no waste yet. Add 10% (round up) before you buy.
| Linear feet needed | 8 ft boards | 12 ft boards | 16 ft boards |
|---|---|---|---|
| 50 ft | 7 | 5 | 4 |
| 100 ft | 13 | 9 | 7 |
| 150 ft | 19 | 13 | 10 |
| 200 ft | 25 | 17 | 13 |
| 300 ft | 38 | 25 | 19 |
| 500 ft | 63 | 42 | 32 |
Bare board counts = ceil(linear feet ÷ board length), no waste. Longer boards mean fewer pieces but more drop waste if your part lengths don't divide evenly — match board length to your cut list where you can.
When to use this lumber calculator
Reach for it whenever a project is priced in boards but planned in total length — which is most framing and woodworking. It turns a tally of run lengths into a shopping list and a budget.
- Framing walls and decks — total the studs, plates, joists, rim and blocking into linear feet, then convert to boards.
- Building fences — rails and pickets bought in fixed lengths from a total run.
- Furniture and woodworking — where rough stock is sold by the board foot and you need the volume, not just the count.
- Pricing a material list — multiply boards by price per board for a fast, defensible budget line.
Waste factor: how much extra lumber to buy
Order the exact run and you will come up short. Every cut leaves a piece too short to reuse, some boards arrive cupped, bowed or split and get culled, and layouts change once the work starts. A waste margin covers all of it.
The 10–15% rule
For straight, simple runs of framing, 10% is the standard margin. For walls with many door and window openings, or a cut list full of short awkward lengths that don't divide cleanly into stock board lengths, go to 15% — the drop waste from trimming long boards into short parts adds up fast. The calculator defaults to 10% and adjusts from 0 to 25%.
Why board length matters as much as the percentage
Two boards of the same total length can waste at completely different rates. A run of 5-foot parts cut from 8-foot boards leaves a 3-foot offcut every time — over a third wasted — while the same parts from 10-foot boards (two 5-footers, no drop) waste almost nothing. Matching board length to your part lengths often saves more than padding the waste percentage.
Lumber definitions
Sources and references
The nominal-vs-actual sizing, the board-foot formula, and the waste-factor guidance follow standard lumber and framing references:
- Lowe's — Lumber Buying Guide: the nominal-vs-actual size chart (a 2×4 is 1.5" × 3.5") and standard board lengths.
- Lumber — Wikipedia: ALSC softwood dimensional-lumber standards, the surfaced (dressed) size convention, and the nominal-size naming system.
- Board foot — Wikipedia: the board-foot definition (1 BF = 144 cubic inches) and the nominal thickness × width × length ÷ 12 formula.
- This Old House — How to Estimate Framing Materials: counting boards from a takeoff and adding a waste allowance for cuts and defects.
- Angi — Lumber Cost Guide: typical board pricing and the 10–15% waste margins used in framing estimates.
How accurate is this lumber calculator?
The board math is exact. Dividing your linear feet by the board length and rounding up gives the precise number of whole boards, and the board-foot figure uses the standard nominal-size formula to the decimal. If your linear-feet total is right, the board count is right.
The estimate's accuracy lives in two inputs you control. First, the linear-feet total: it must come from a real cut list or takeoff — the calculator can't see the offcuts your part lengths will create, so a run of awkward short pieces may need more than the count suggests even with waste added. Second, price: lumber prices swing with the market, the species and the grade, so treat the cost as a planning figure and confirm it at the yard. When in doubt, round the waste factor up — a spare board is cheaper than a second trip.
Frequently asked questions about the free lumber calculator
About this lumber calculator
This lumber calculator runs entirely in your browser. Nothing you enter is uploaded or stored — every figure is computed locally the moment you change an input, so you can try board lengths, sizes, and waste margins as fast as you can type. The board math is exact; the cost is an estimate that moves with your local price per board.
Need related material estimates? See the construction calculators shelf for concrete, plywood, decking, and more, or browse every tool in the full calculator directory.