Every transaction in the gem and jewellery trade starts with a weight. A stone sold as 1.00 carat and weighed as 0.99 is a different stone with a different price, so the scale on your desk is not an accessory - it is the instrument your margins depend on. This guide explains how to choose between pocket, bench and lab scales, and which specifications actually protect you.
Carat scales vs gold scales: what is the difference?
The difference is readability and capacity. Diamond and gemstone scales weigh small amounts with very fine resolution, typically 50 to 300 grams capacity at 0.001g (0.005ct) readability. Gold and silver scales weigh heavier items at coarser resolution, typically 300g to several kilograms at 0.01g or 0.1g. One scale cannot do both jobs well: fine readability and high capacity work against each other in load-cell design.
What does readability mean, and how much do you need?
Readability is the smallest step the display shows. For diamonds and gemstones, 0.001g - equal to 0.005ct - is the working standard, because carat weights are stated to two decimal places and rounding rules demand better resolution than the stated figure. For melee parcels, that same 0.001g readability keeps per-stone averages honest. For gold, 0.01g is standard for jewellery and 0.1g acceptable for bullion-scale weights.
Which type of scale fits how you work?
Pocket and portable scales
For buying trips, trade shows and site visits. Modern pocket carat scales deliver 0.001g readability in a case that fits a jacket pocket, usually with a wind shield and calibration weight included. Their limitation is drift: recalibrate after travel and let them warm up before weighing.
Bench diamond and gemstone scales
The daily workhorse for offices and counters. Bench diamond and jewellery scales add a stable weighing chamber, faster settling and better repeatability than pocket units. If a scale gets used more than a few times a day, this is the category to buy.
Laboratory balances
For certification work, lab-grade carat scales offer 0.0001g class readability, full draft shields and internal calibration. Buy this class when your weights go on grading reports.
Gold and silver scales
For bullion and heavy jewellery, gold and silver bench scales provide the capacity headroom fine scales lack, and portable gold scales cover buying on the road.
Comparison at a glance
| Type | Typical capacity | Readability | Best for |
|---|---|---|---|
| Pocket carat scale | 50-100g | 0.001g | Buying trips, shows |
| Bench diamond scale | 100-300g | 0.001g | Daily office weighing |
| Lab balance | 100-220g | 0.0001g | Certification, labs |
| Gold bench scale | 600g-3kg+ | 0.01-0.1g | Bullion, heavy jewellery |
Calibration: the habit that keeps weights honest
A scale is only as accurate as its last calibration. Three rules serve every desk well: calibrate with a certified test weight after any move or transport; let electronic scales warm up for several minutes before precise work; and keep scales away from drafts, vibration and direct sun. Certified calibration weights and accessories cost little compared to a single mis-weighed parcel.
Do you need a legal-for-trade scale?
If you sell by weight to the public, many jurisdictions require a certified, sealed legal-for-trade scale. Requirements differ by country, so check your local weights-and-measures rules; for internal grading, sorting and buying, a standard precision scale is sufficient. Our Bangkok team can advise on what fits your market - contact us with your use case.
The bottom line
Buy readability for stones, capacity for metal, and never share one scale between the two jobs. Start with a bench carat scale for the office and add a pocket scale for travel. Browse the full weighing scales collection - genuine calibrated stock, shipped worldwide from Bangkok since 2001.