How to Calculate Board Feet
Three Parts:Calculating Board Feet with Length in InchesCalculating Board Feet with Length in FeetCalculating Cost by Board Foot
Hardwood board is sold in random widths and lengths, so you will need to calculate the board footage of any hardwood you plan to purchase. Board footage is actually a measurement of volume; as such, you'll need to know the length, width, and depth/thickness of the board to calculate it. The length can be in either inches or feet.
Steps
Part 1 Calculating Board Feet with Length in Inches
- 1Measure the length, width, and depth in inches. Use a stiff tape measure to measure the length, width, and depth of the board. Each measurement should be taken separately and recorded in inches.
- Using this method of calculation, you must know the length, width, and depth of each board in inches. Round fractional sizes to the nearest quarter-inch.
- Note that board thickness is always expressed in quarter-inches, even when you have a whole number. In other words, 1-inch thick board would be expressed as four-quarter (4/4) board. When calculating board feet, however, you should still use the actual measured number of inches for the sake of simplicity.
- If you are buying pre-measured, marked hardwood from a reliable source, you can skip this step and begin your calculations. Measuring the hardwood board yourself is always recommended when possible, though.
- Example: Calculate board feet for five-quarter (5/4) hardwood measuring 26 inches long and 4.5 inches wide.
- Note that “five-quarter” hardwood is 1.25 inches thick.
- 2Multiply these three measurements together. Multiply the measured length, width, and depth of the board. Write down the product of all three measurements.
- During this part of the calculation, you are actually determining the volume of the board. As such, your answer will need to be in cubic inches.
- Example: length * width * depth = 26 inches * 4.5 inches * 1.25 inches = 146.25 cubic inches
- 3Divide the product by 144. Divide the product you just calculated by 144 cubic inches. Write down the quotient you calculate.^{[1]}
- Note that 1 board foot equals 144 cubic inches. That is the reason you must divide the board volume—the number of cubic inches—by 144.^{[2]}
- Example: 146.25 cubic inches / 144 cubic inches = 1.02 board feet
- 4Double check the result. You should now know the board feet of the hardwood you're looking at. Run through the calculations one more time to verify your answer.
- Example: Board feet = [length * width * depth] / 144 = [26 * 4.5 * 1.25] / 144 = 146.25 / 144 = 1.02 board feet
Part 2 Calculating Board Feet with Length in Feet
- 1Measure the length in feet. Use a stiff tape measure to measure the length of the board. Record this measurement in feet.
- When using this method of calculation, you need to know the length of the hardwood board in feet and not in inches. Fractional feet should be written as x / 12, with x equaling the number of inches.
- It is always a good idea to measure the hardwood boards yourself before purchasing them. If you intend to buy pre-measured, marked hardwood boards from a trusted source, however, you can technically skip the measuring steps and jump directly into the calculations.
- Example: Calculate board feet for a piece of hardwood measuring 2-2/12 feet long.
- The fraction here can be simplified, giving you a measurement of 2-1/6 feet.
- Alternatively, you can divide the fraction into a decimal, giving you a measurement of 2.17 feet.
- 2Measure the width and depth in inches. Use the same stiff tape measure to measure the width and depth of the same board. Take each measurement separately and record them both in inches.
- Width and depth are both measured in inches, not in feet. Round fractional sizes to the nearest quarter-inch.
- Board depth/thickness is referred to by the quarter-inch, so 1-inch thick board would be described as four-quarter board. You will still use the actual number of inches in your board feet calculation, though.
- Example: Calculate board feet for 2.17 feet of five-quarter (5/4) hardwood measuring 4.5 inches wide.
- Note that "five-quarter" hardwood is 1.25 inches thick.
- 3Multiply the three measurements together. Multiply the length measurement with the width and depth measurements. Write down the product of all three measurements.
- You're actually calculating the volume of the board during this step. Since one of the measurements is not in inches, however, the product will not be in cubic inches. Instead, it will be in feet by squared inch (ft*in^{2}).
- Example: length * width * depth = 2.17 feet * 4.5 inches * 1.25 inches = 12.21 ft/in^{2}
- 4Divide the product by 12. Divide the product you just calculated by the number 12. Save the quotient you calculate during this step.^{[3]}
- Since the calculated board volume is in ft*in^{2} instead of cubic inches, you cannot divide the volume by the amount of cubic inches per board foot (144 cubic inches).
- Instead, you must divide the volume by a measurement taken in ft*in^{2}. There are 12 ft*in^{2} per board foot.
- Example: 12.21 ft/in^{2} / 12 ft/in^{2} = 1.02 board feet
- 5Double check the result. At this point, you've already calculated the board feet of the hardwood board in front of you. It is still a good idea to work through the same calculations one more time to verify the accuracy of your answer, though.
- Example: Board feet = [length * width * depth] / 12 = [2.17 * 4.5 * 1.25] / 12 = 12.21 / 12 = 1.02 board feet
Part 3 Calculating Cost by Board Foot
- 1Calculate board feet for each piece of wood. Use either method of calculation to find the board feet of each piece of wood you plan to purchase.
- Note that this will only work if there is one consistent cost per board foot for each piece of wood included in your total board footage. Do not include boards priced at a different rate in your cost calculation.
- Example: Calculate the cost of three separate pieces of hardwood available at a price of $5.45 per board foot. The first piece is 4.3 board feet, the second is 6.8 board feet, and the third is an even 2 board feet.
- 2Add the board footage together. Once you have calculated the board feet of each piece of hardwood, add the amounts together to find the total board footage.
- Example: Total board footage = 4.3 board feet + 6.8 board feet + 2 board feet = 13.1 board feet
- 3Multiply by the price per board foot. Multiply the total board footage by the price per board foot of the hardwood.
- Example: Total board footage * cost per board foot = 13.1 board feet * $5.45 = $71.40
- 4Double check your calculations. You should now know the cost of the hardwood based on board footage. Verify the accuracy of your answer by working through the calculations again.
- Example: Total cost = total board footage * cost per board foot = 13.1 * 5.45 = $71.40
Sources and Citations
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Categories: Mathematics | Woodworking