Calculate CBM

CBM stands for “cubic meters.” When abbreviated in this manner, this measurement typically refers to the total number of cubic meters required to pack and ship packages. The precise method of calculating CBM will vary depending on the shape of the involved unit.

Steps

Calculating CBM per Rectangular Prism

  1. Measure the sides of the carton. You'll need to know the length, width, and height of the rectangular carton. Use a measuring stick to find all three distances and mark them down separately.
    • CBM is a measurement of volume, so you'll be using the standard volume formula for rectangular prisms.
    • Example: Calculate the CBM of a rectangular package with a length of 15 cm, a width of 10 cm, and a height of 8 cm.
  2. Convert the measurements into meters, if necessary. For small packages, you may end up taking measurements in centimeters, inches, or feet. Before you can calculate CBM, you'll need to convert each measurement into its equivalent value in meters.
    • The exact conversion equation will vary depending on the unit used in your original measurements.
    • Example: The original measurements were taken in centimeters. To convert centimeters into meters, divide the number of centimeters by a conversion factor of 100. Repeat this process for all three measurements. The unit for the length, width, and height should be the same.
      • Length: 15 cm / 100 = 0.15 m
      • Width: 10 cm / 100 = 0.1 m
      • Height: 8 cm / 100 = 0.08 m
  3. Multiply the length, width, and height. Following the formula for CBM, multiply together the length, width, and height of the rectangular prism.[1]
    • Written in abbreviated form the formula you'll need to use looks like: CBM = L * W * H
      • Where L = length, W = width, and H = height
    • Example: CBM = 0.15 m * 0.1 m * 0.08 m = 0.0012 cubic meters
  4. Note the CBM. The product of the original three dimensions will be both the volume and CBM of the individual package unit.
    • Example: The CBM of this package is 0.0012. This signifies that the package will take up 0.0012 cubic meters of space.

Calculating CBM per Cylindrical Unit

  1. Measure the length and radius of the carton. When dealing with tubes and other cylindrical packages, you'll need to know the height or length of the cylinder, as well as the radius of its circular sides. Find these measurements using a measuring stick, then write both down separately.
    • Since CBM is actually a measurement of volume, you'll need to use the standard volume formula for cylinders when calculating the CBM of a cylindrical package.
    • Note that the radius of the circular side is half its diameter, and the diameter is the distance from one side of the circular face to the other. To measure the radius, measure the diameter of one circular face and split the number in half.
    • Example: Calculate the CBM of a cylindrical package with a height of 64 inches and a diameter of 20 inches.
      • Find the radius of this package by dividing the diameter in half: 20 inches / 2 = 10 inches
  2. Convert these measurements into meters, when applicable. For many small packages, you may naturally take measurements in centimeters, inches, or feet. You must convert such measurements into their equivalent value in meters before calculating cubic meters.
    • The conversion factor you'll need to use will depend upon the unit used in your original measurement.
    • Example: These original measurements were taken in inches. To convert inches into meters, you need to divide the number of inches by a conversion factor of 39.37.[2] Repeat this process for both measurements.
      • Height: 64 inches / 39.37 = 1.63 m
      • Radius: 10 inches / 39.37 = 0.25 m
  3. Plug the values into the volume equation. To find the volume and CBM of a cylinder, you need to multiply the cylinder's height with its radius. You must then multiply the product of those two values by the fixed value of pi.[3]
    • When written in abbreviated form, the formula you need to use looks like: CBM = H * R2 * π
      • Where H = height, R = radius, and π = the constant pi, 3.14
    • Example: CBM = 1.63 m * (0.25 m)2 * 3.14 = 1.63 m * 0.0625 m2 * 3.14 = 0.32 cubic meters
  4. Note the CBM. The product you calculated during the previous step should be the volume and CBM of the individual cylindrical unit.
    • Example: The CBM of this package is 0.32, meaning that it will take up 0.32 cubic meters of space.

Calculating CBM per Irregular Unit

  1. Measure the greatest distances. You'll need to treat an irregularly shaped package like a rectangular package when calculating CBM, but since there is no consistent length, width, and height, you must identify the longest, widest, and tallest portions of the package and measure those maximum distances with some type of measuring stick. Mark each of these three measurements down separately.
    • Even though CBM is a measurement of volume, there is no standard formula to use when calculating the volume of an irregularly shaped three-dimensional object. Instead of finding an exact volume, you can only calculate an estimated one.[4]
    • Example: Calculate the CBM of an irregularly shaped package with a maximum length of 5 feet, a maximum width of 3 feet, and a maximum height of 4 feet.
  2. Convert the measurements into meters, if needed. If you inadvertently took the length, height, and width in centimeters, inches, or feet, you need to convert those measurements into meters before calculating the package's cubic meters.
    • Note that the conversion factor will vary based on the unit used when originally measuring the three sides of the package.
    • Example: The original measurements in this example were taken in feet. To convert feet into meters, divide the number of feet by a conversion factor of 3.2808.[5] Repeat this process for all three measurements.
      • Length: 5 ft / 3.2808 = 1.52 m
      • Width: 3 feet / 3.2808 = 0.91 m
      • Height: 4 feet / 3.2808 = 1.22 m
  3. Multiply the length, width, and height. Treat the package as though it were a rectangular unit and multiply together the maximum length, width, and height of the unit.
    • If written in abbreviated form, the formula will look like: CBM = L * W * H
      • Where L = length, W = width, and H = height
    • Example: CBM = 1.52 m * 0.91 m * 1.22 m = 1.69 cubic meters
  4. Note the CBM. After finding the product of the three maximum measurements, you should know the volume and CBM of this individual, irregularly shaped package.
    • Example: The estimated CBM of this package is 1.69. Even though it may not fill the entire space, the unit will require 1.69 cubic meters of space to pack and ship.

Calculating CBM per Total Shipment

  1. Find the unit CBM for each batch. If the shipment contains multiple batches, and each batch consists of a certain number of equally sized packages, you can calculate the total CBM without calculating the CBM of each individual carton. You'll need to start by finding the unit CBM of the standard carton in each batch.
    • Use whichever unit CBM calculation is needed based on the shape of the package (rectangular, cylindrical, or irregular).
    • Example: The rectangular, cylindrical, and irregular packages described in the previous sections of this article are all being delivered in a single shipment. This means that unit CBM of the rectangular batch is 0.0012 m3, the unit CBM of the cylindrical batch is 0.32 m3, and the unit CBM of the irregular batch is 1.69 m3.
  2. Multiply each unit CBM by the number of units. Within each batch, multiply the unit CBM you calculated by the number of units or packages in that particular batch. Repeat this process until you have gone through each batch within the shipment.
    • Example: There are 50 packages in the rectangular batch, 35 packages in the cylindrical batch, and 8 packages in the irregular batch.
      • Rectangular batch CBM: 0.0012 m3 * 50 = 0.06 m3
      • Cylindrical batch CBM: 0.32 m3 * 35 = 11.2 m3
      • Irregular batch CBM: 1.69 m3 * 8 = 13.52 m3
  3. Add the batch CBM totals together. After calculating the total CBM of each batch within the shipment, you'll need to add those totals together to find the overall CBM of the entire shipment.
    • Example: Total CBM = 0.06 m3 + 11.2 m3 + 13.52 m3 = 24.78 m3
  4. Note the total CBM of the shipment. Review your work. At this point, you should know the total CBM of the entire shipment. No further calculations should be needed.
    • Example: The total CBM of the entire shipment, including all three batches, will be 24.78. This means that 24.78 cubic meters of space are required to pack and ship all of the units involved.

Related Articles

Sources and Citations

  1. ↑ http://www.nobleship.com/cbm-formula.html
  2. ↑ http://www.metric-conversions.org/length/inches-to-meters.htm
  3. ↑ http://shippingandfreightresource.com/calculation-of-cbm-update/
  4. ↑ http://www.utsexpress.com/faqdetails.php?faqid=25
  5. ↑ http://www.metric-conversions.org/length/feet-to-meters.htm
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