Board Foot Calculator for Lumber and Cost
Enter one board size and how many you need, and the calculator gives the board feet, the amount to buy with waste and the cost.
Your measurements
Enter one board size and how many you need. Everything updates as you type.
One board
4/4 is 1 in thick. Hardwood yards price on this rough thickness, not the planed one.
Measure the narrowest point of the board, or the width the yard quotes.
How many, and the price
Boards of the size above. For a mix of sizes, run each size and add the totals.
15% is a common starting point for hardwood. Allow more for knotty stock or a tight grain match.
From the yard's price list. Leave at 0 if you only need the board feet.
Results
Board feet to buy
bd ft
= 10 boards, 4/4 × 6" × 8 ft
40 board feet of boards plus 15% extra, about $368.00 at $8.00 per board foot.
- One board
- 4bd ft
- 1" × 6" × 8 ft
- Before waste
- 40bd ft
- 0.0944 m³ of wood
- Cost
- $368.00
- $320.00 before waste
How this was calculated
Board feet, waste and cost, with your numbers.
How this was calculated
Board feet, waste and cost, with your numbers.
Step 1: Board feet in one board
thickness (in) × width (in) × length (ft) ÷ 12
= 1 × 6 × 8 ÷ 12
= 4 board feetOne board foot is a piece 1 inch thick, 12 inches wide and 12 inches long (144 cubic inches). Dividing by 12 instead of 144 works because the length is in feet.
Step 2: Multiply by the number of boards
board feet per board × boards
= 4 × 10
= 40 board feetThis is what the boards measure, before any waste.
Step 3: Add the waste allowance
board feet × (1 + waste)
= 40 × 1.15
= 46 board feet to buyExtra for defects, knots, snipe and cutting mistakes. The percentage is your choice; 15% is a common starting point for hardwood.
Step 4: Cost
board feet to buy × price per board foot
= 46 × $8
= $368.00Without the waste allowance the boards you need come to $320.00. Rough lumber is priced on its rough thickness, so measure the thickness the yard quotes (4/4, 8/4), not the planed thickness.
In short
Board feet = thickness (in) × width (in) × length (ft) ÷ 12. 10 boards of 4/4 × 6 in × 8 ft are 40 board feet, or 46 with 15% extra.
It uses the rough thickness in quarters that hardwood yards price on.
Board feet in common boards
Board feet in one board 6 inches wide and 8 feet long, by rough thickness.
| Rough thickness | Thickness | Board feet | Per foot of length |
|---|---|---|---|
| 4/4 | 1" | 4 | 0.5 |
| 5/4 | 1.25" | 5 | 0.625 |
| 6/4 | 1.5" | 6 | 0.75 |
| 8/4 | 2" | 8 | 1 |
| 10/4 | 2.5" | 10 | 1.25 |
| 12/4 | 3" | 12 | 1.5 |
| 16/4 | 4" | 16 | 2 |
Worked example: 10 boards, 4/4 × 6 in × 8 ft
15% extra for waste at $8 per board foot.
Step 1: Board feet in one board
thickness (in) × width (in) × length (ft) ÷ 12
= 1 × 6 × 8 ÷ 12
= 4 board feetOne board foot is a piece 1 inch thick, 12 inches wide and 12 inches long (144 cubic inches). Dividing by 12 instead of 144 works because the length is in feet.
Step 2: Multiply by the number of boards
board feet per board × boards
= 4 × 10
= 40 board feetThis is what the boards measure, before any waste.
Step 3: Add the waste allowance
board feet × (1 + waste)
= 40 × 1.15
= 46 board feet to buyExtra for defects, knots, snipe and cutting mistakes. The percentage is your choice; 15% is a common starting point for hardwood.
Step 4: Cost
board feet to buy × price per board foot
= 46 × $8
= $368.00Without the waste allowance the boards you need come to $320.00. Rough lumber is priced on its rough thickness, so measure the thickness the yard quotes (4/4, 8/4), not the planed thickness.
Before you buy
- Ask the yard whether it prices by rough or surfaced thickness. Most hardwood dealers use the rough thickness (4/4, 8/4).
- Softwood and construction lumber is usually sold by the piece or the linear foot, not by the board foot.
- Board feet only measure wood volume. Planing 4/4 down to ¾ inch leaves you with less usable wood than you paid for, so allow for it in the waste figure.
Board feet: common questions
The formula, quarters and waste.
How do you calculate board feet?
Multiply thickness in inches by width in inches by length in feet, then divide by 12. A board 1 inch thick, 6 inches wide and 8 feet long is 1 × 6 × 8 ÷ 12 = 4 board feet. If you have all three in inches, divide by 144 instead.
What does 4/4 or 8/4 mean on hardwood?
It is the rough thickness in quarters of an inch: 4/4 is 1 inch, 5/4 is 1¼ inch, 6/4 is 1½ inch and 8/4 is 2 inches. Yards price and measure board feet on that rough thickness, even though the board is planed thinner before you use it.
How much extra hardwood should I buy?
A common allowance is 15% for defects, knots and cutting errors, and 20% to 25% if you need to match grain or the boards are rough. It is your call: the calculator takes whatever percentage you set.
Is a board foot the same as a square foot?
No. A square foot is an area. A board foot is a volume of 144 cubic inches, which is why thickness matters: a 2 inch thick board has twice the board feet of a 1 inch board of the same size.