A cannabis scale is accurate when it is verified against certified test weights, sits level on a stable surface, and holds a current legal-for-trade certification from your state or county weights and measures office. Scales used for legal cannabis sales must meet NIST Handbook 44 tolerances, be checked at the start of every shift, and be recalibrated after any move, drop, or large temperature swing.
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What does legal for trade mean for a cannabis scale?
A legal-for-trade scale is one a weights and measures official has tested and sealed for commercial use. It carries a certificate, a tamper seal, and a rated capacity and resolution that fit how you sell. A kitchen scale bought online is not legal for trade, even if it displays to 0.01 g.
How often should a cannabis scale be calibrated?
Run a test-weight check at the start of each shift and calibrate whenever that check lands outside tolerance. Full certification follows the interval your state sets, often once a year.
cannabis scale accuracy and calibration
Recalibrate right away after any of these events:
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- Moving the scale to another room, counter, or store
- A drop, bump, or spill on the weighing pan
- A power surge, battery swap, or long stretch powered off
- A room temperature shift of roughly 10 degrees Fahrenheit or more
How do you calibrate a cannabis scale step by step?
- Let the scale warm up for the period in the manual, usually 15 to 30 minutes.
- Place it on a rigid, level surface away from vents, doors, and vibrating equipment.
- Zero the display and confirm it returns to zero after you lift the test weight off.
- Set a certified test weight near your most common sale size, such as 10 g or 100 g.
- Record the reading. If it falls outside tolerance, enter calibration mode and adjust to the weight value.
- Repeat at mid-range and near capacity, then log the results and your initials.
What tolerance counts as accurate?
Handbook 44 expresses tolerance as a multiple of the scale's verification division, so a 0.1 g scale has to hold within a fraction of a gram at normal retail loads. A drift of several tenths of a gram at 28 g is a fail, not a rounding quirk. Check tolerance against the class printed on the scale's data plate.
What causes a cannabis scale to drift?
- Drafts from HVAC vents, fans, and propped-open doors
- Vibration from a grinder, receipt printer, or heavy foot traffic
- Residue, trichomes, or spilled concentrate on the pan
- Overloading past rated capacity, which can bend the load cell for good
- Weak batteries or an unstable power supply
- Direct sun and rapid temperature swings
Why does accuracy matter beyond the label?
States audit commercial weighing devices, and a failed inspection can pull a scale from service and trigger fines. Undermeasure shortchanges the customer and undermines the net weight claim on the package. Overmeasure quietly drains margin across hundreds of transactions, and both outcomes surface in a compliance review.
What should a calibration log include?
Keep a written or digital log for every scale in the building, and have it ready for an inspector.
- Scale ID, make, model, capacity, and resolution
- Date, time, and initials of the person who ran the check
- Test weight values used and their certification dates
- As-found and as-left readings
- Seal or certificate number from the weights and measures inspector
What test weights should a dispensary keep on hand?
Buy certified weights that bracket your normal sale sizes, such as 1 g, 10 g, 100 g, and 500 g. Store them in a case, handle them with gloves or forceps, and send them out for recertification on the schedule your state requires. Weights that are out of certification make your calibration record worthless.
Can a customer check a dispensary scale?
Yes, within reason. Ask to see the seal or certificate, and watch that the budtender tares the container before weighing the flower. A sealed legal-for-trade scale carries a visible sticker, and staff should be able to point to it.
How do you keep a scale accurate between calibrations?
Treat the scale as a piece of regulated equipment, not counter clutter. Keep it on a dedicated surface, wipe the pan between customers, and cover it when the shop closes. Any employee who weighs product should know how to run a test-weight check and where the log lives.