The short answer
For checking what you bought, you want a pocket scale with 0.01 g resolution, 100 g or more of capacity, a tare button, and a calibration weight you can trust. Anything less is decoration. The scale behind the dispensary counter is a different animal: it has to be legal for trade, meaning it passed a type evaluation and gets inspected under state weights and measures rules. Your $20 pocket scale is not legal for trade, and it does not need to be. It needs to be honest enough to catch a short eighth.
Why a fraction of a gram is real money
Cannabis sells in fractions of an ounce: an eighth is 3.5 g, a quarter is 7 g, an ounce is 28.35 g. At $40 an eighth, 0.1 g is about $1.14. At $60 an eighth, the same sliver runs $1.71. That gap is the whole reason a scale belongs in your kit. A 0.1 g resolution scale steps in chunks that big, so a short eighth and a full one can look identical. A 0.01 g scale shows you 3.48 and 3.51 separately. I look for that resolution first and ignore most of what the packaging brags about.
What legal for trade actually means
Commercial scales in the US fall under NIST Handbook 44, which sets accuracy classes, tolerance bands, and inspection requirements that states adopt into their own rules. A legal-for-trade scale is type evaluated, then inspected and sealed by a weights and measures official. Cannabis regulators layer their own requirements on top. Washington requires licensed retailers to use approved commercial scales, and Colorado requires cannabis businesses to use scales certified by the state measurement standards program. If you want to know whether the counter scale is on the level, look for the inspection sticker and read the date. It is a fair question and most budtenders will answer it.
What to look for in a personal scale
- Resolution of 0.01 g. Fine enough to see a tenth of a gram move. Skip 0.1 g scales for flower.
- Capacity of at least 100 g. You need room to tare a jar or a small tray and still weigh an ounce.
- Tare button. Non-negotiable. A glass jar lid can add 10 g or more to the reading.
- Recalibration. A scale you cannot calibrate will drift and then lie with confidence.
- Windshield or cover. At 0.01 g, a ceiling fan or an open window is enough to spoil the reading.
- Backlit display. Small thing, but you will weigh in low light more often than you expect.
A 60-second check before you trust any number
- Zero the scale and let it sit for 10 seconds. If the display wanders off zero, stop there.
- Weigh the calibration weight, or a clean US nickel. A new nickel is 5.000 g by Mint specification. A reading from 4.95 to 5.02 g is normal for a circulated coin; a reading of 5.4 g means the scale is out.
- Weigh the same object three times, lifting it off between readings. You want the same number, or within one step.
- Check the battery. A weak battery is the most common cause of a scale that reads high or low at random.
Sealed packages and the average rule
Convenience pushed weighing back to the producer. You buy a sealed jar, a pre-roll pack, or a delivery bag, and the net weight on the label is your only evidence. Net content rules (NIST Handbook 133, also from the weights and measures world) allow one package to run a little under the declared weight as long as the lot average meets or beats it. So a 3.5 g eighth reading 3.45 g on your scale is not proof of fraud by itself. A stack of them reading 3.4 g is a pattern, and that pattern is worth a conversation with the shop.
cannabis scale that weighs ounces
Price per gram, the only comparison that matters
Once you trust the weight, divide price by grams. A $45 eighth is $12.86 per gram. A $120 half ounce (14 g) is $8.57 per gram. A $200 ounce is $7.05. Pre-rolls, delivery fees, and taxes hide those numbers. Running the division takes ten seconds and it changes what you buy.
Bottom line
Buy a 0.01 g pocket scale with tare and calibration, keep a known weight with it, and check the shop inspection sticker when you are curious. Nothing here is exotic. It is the same routine a deli uses, applied to a product where the margin is measured in tenths of a gram.