All scales used for commercial purposes must meet strict standards for accuracy and customer visibility established in the Missouri Code of State Regulations. Appropriate and suitable scale must be approved by the Missouri Department of Agriculture’s Division of Weighs, Measures, and Consumer protection on an annual basis, and must bear a National Type Evaluation Program (NTEP) Certificate of Conformance before commercial use.

Selecting a suitable device for Medical Marijuana applications is in everyone’s best interest. The proper selection of scale must be based upon the specific application in which they are used. Missouri Law requires all scales to meet the requirements of NIST Handbook 44 Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices. Located in the Scales Code, section 2.20., paragraph UR.1. Selection Requirements, information can be found on number of scale divisions, value of the verification scale division, and minimum capacity for scales. Table 7a. - Typical Class or Type of Device for Weighing Application shows that all laboratory scales must be Class I or II. Additionally, the scales code discusses prescription scales as being Class I or II. This means that all laboratory and packaging scales must meet Class I or II requirements.

There are some cases where a Class III scale may be the best choice for the application at hand. Since airflow and vibration have a significant effects on weighing quality, a Class III scale may be appropriate for use in loosely controlled environments such as greenhouses and cultivation facilities to obtain raw product weights. Only in these areas will the use of a Class III scale be permitted. Once the product is processed further into smaller and smaller quantities, a Class I or II scale must be used. The suitability of the scale selection made by the user will be confirmed by the Weights & Measures official.

Step 1: Things to consider before purchasing a scale:

  • Range of Weighing (minimum and maximum capacities)
  • Division (weighing increment) size
  • Precision Class (i.e. scales that comply with Accuracy Class I & II parameters)

Step 2: Placing into Service:

  • A registered service company can be used to install and place the device into commercial service, pending inspection by a Weights, Measures, and Consumer Protection official. You can view a list of registered service companies in Missouri.
  • Legal-for-trade scales must be “inspected, tested and sealed” by the division of Weights, Measures and Consumer Protection.
  • Because of their sensitivity, precision scales may need to be verified and recalibrated when moved to another location within a production facility or retail establishment.
  • Contact the division of Weights, Measures and Consumer Protection to request an inspection of a device that has not been placed into commercial service by a registered service company.

Step 3: Using and Maintaining:

  • The owner is responsible for ensuring accuracy and proper maintenance of a commercial scale, benefiting all parties involved.
  • Scales must be installed and operated according to the manufacturer’s instructions, as well as according to Missouri laws and regulations.
  • Scales must be placed on a solid, level surface.
  • Deduct “TARE” (packaging, wrappings, containers, etc.) to determine “NET” weight (NET = GROSS - TARE).

Sales by Weight

When sales are made by weight, a business needs to determine weight of the following:

  • Containers/packages of trimmings
  • Containers/packages of product, and
  • Packages of dried flowers

You must deduct “TARE” (weight of the packaging material, wrappings, containers, labels, etc.) to determine the “NET” weight of the product. (NET=GROSS-TARE). This may include, but is not limited to, packages of:

  • Usable buds or flower
  • Edibles
  • Topical ointments, creams, balms, etc.
  • Shatter or other concentrates

Sales by Volume

Products sold in liquid form are sold by volume, e.g., milliliters (ml) and fluid ounces (fl oz). This may include, but is not limited to, packages of:

  • Oils
  • Tinctures
  • Extracts

Additional Resources