Quick answer
Legal purchase limits cap how much cannabis one customer can buy in one visit. Scale calibration proves the weight on the label matches the weight in the bag. Most adult-use states set limits by product type: about 28 g of flower, 8 g of concentrate, and 800 mg of THC in edibles. A scale used to price cannabis is a commercial weighing device. It must pass state inspection, hold NTEP certification, and stay inside the tolerance listed in NIST Handbook 44.
how to use a cannabis scale properly
Purchase limits by state
Limits apply per transaction, per customer, per day. Numbers differ by state and by medical status.
cannabis scale accuracy and calibration
- California: 28.5 g flower, 8 g concentrate, 800 mg THC in edibles, adults 21 and older.
- Colorado: 28 g flower, 8 g concentrate, 800 mg edible THC, adults 21 and older.
- Washington: 28 g flower, 7 g concentrate, 16 oz solid edible, 72 oz liquid edible.
Several states count limits in flower equivalent. One ounce equals 8 g of concentrate or 800 mg of edible THC. A customer who buys 14 g of flower plus 4 g of concentrate has used half an ounce plus half an ounce. That is the full limit.
Possession limits and purchase limits are not the same number
A store limit is a sale limit. A possession limit is what a person may carry at one time. Some states match them. Others let a customer buy the daily maximum and hold more at home. Medical patients often get higher caps than adult-use customers in the same state. Staff should check the customer type before ringing a sale.
Why cannabis scales are regulated
Cannabis sold by weight falls under state weights and measures law. The device is the cash register for flower and concentrate. A scale that reads high overcharges the customer. A scale that reads low shortens the product and breaks the label. Both are violations.
Certification and inspection
The National Conference on Weights and Measures runs the National Type Evaluation Program (NTEP). NTEP issues a Certificate of Conformance for each scale model. Most states require that certificate before a dispensary can use the scale. A state inspector then places a seal on the device. Breaking the seal voids the approval.
Calibration steps
- Level the scale. Check the bubble or the foot pads.
- Let the device reach room temperature. Cold units drift.
- Run a zero check. The display must read 0.00 g with an empty pan.
- Place a certified test weight on the pan. NIST-traceable weights are the standard.
- Compare the reading to the weight value. Record both numbers.
- Adjust the scale if the reading falls outside tolerance. Repeat the test.
- Log the date, the weight ID, the reading, and the initials of the person who ran the test.
Tolerances and test weights
Handbook 44 expresses tolerance in scale divisions, written as "e." Acceptance tolerance is one division. Maintenance tolerance is two divisions. A scale with e = 0.01 g may not error by more than 0.01 g at inspection. Test weights must be traceable to NIST. Class 1 or Class 2 weights fit most dispensary scales. Weights get recertified on a schedule, often every year or two.
Daily practice at the counter
- Tare the jar or tray before adding product.
- Weigh flower on the same scale the store uses for pricing.
- Print the weight on the label to two decimals.
- Keep the scale on a solid counter away from vents and doorways.
- Recheck zero between customers.
Records to keep
Keep calibration logs, weight certificates, the NTEP certificate, and the state inspection report. Retention periods run 1 to 3 years depending on the state. Inspectors ask for these documents during a site visit.
What changes
Limits, tolerance rules, and certification requirements change by legislative session. Verify current numbers with the state cannabis regulator and the state weights and measures office before a store opens or reorders scales.