Guide
Gross Weight vs Net Weight in Jewellery
Gross weight is the whole piece on the scale, stones included. Net weight is the metal alone, gross minus the stone weight. The metal rate is charged on net weight, never on gross — and fine weight, the figure stock is reconciled on, is derived from net weight multiplied by the purity of the metal.
The four figures, in the order they are recorded
A piece of jewellery does not have a weight. It has four, and each one answers a different question. Collapsing them into a single number is the root of most billing disputes and nearly every stock figure that will not reconcile.
| Figure | What it is | What it is for |
|---|---|---|
| Gross weight | The whole piece on the scale, metal and stones together | Physical counts — it is the only figure you can measure without dismantling the piece |
| Stone weight | The part of the gross weight that is not metal | Subtracting, so it must be a number and not a note in a description |
| Net weight | Gross minus stone. The metal alone | Charging the metal rate, and deriving fine weight |
| Fine weight | Net weight multiplied by the fineness of the metal | Reconciling stock, because it is the only figure that adds up across purities |
Why the metal rate is charged on net weight
The rate board quotes a price for gold. A stone is not gold. If a ring weighs 8.500 g on the scale and 1.200 g of that is a stone, then charging today's gold rate on 8.500 g charges the customer for 1.200 g of stone at the price of gold — and separately charges for the stone again on its own line. The same piece is billed twice for the same stone, once at the wrong price.
This is not a rare edge case. It is every stone-set piece in the shop, and at Nepal gold rates the error on a single ring is larger than a day's making charges.
Fine weight comes from net weight, for every metal
Fine weight is how much pure metal a piece actually contains. It is net weight multiplied by the fineness of its purity — and the multiplication is always on net weight, because the stones are not made of the metal whose purity is being applied. That holds for gold and for silver alike; the fineness changes, the rule does not.
| Purity | Fineness | Net weight | Fine weight |
|---|---|---|---|
| 24K gold | 0.999 | 10.000 g | 9.990 g |
| 22K gold | 0.916 | 10.000 g | 9.160 g |
| 18K gold | 0.750 | 10.000 g | 7.500 g |
| 999 silver | 0.999 | 50.000 g | 49.950 g |
| 925 silver | 0.925 | 50.000 g | 46.250 g |
Fine weight matters because it is the only figure that can be added across a tray holding several purities. Two grams of 24K and two grams of 18K are not comparable quantities; 1.998 g fine and 1.500 g fine are, and they belong in the same total. That total is what a monthly stock reconciliation is run against. See tracking gold stock accurately for how the reconciliation itself is done.
Stones: carats, grams, and which one to record
Stone weight is quoted in carats as often as in grams, and the conversion is fixed: one carat is 0.2 grams. A 6-carat stone is 1.200 g. Whichever unit the trade uses, the figure that has to reach the stock record is the one that can be subtracted from gross weight — so it has to be stored as a weight, in the same unit as the gross figure, not as text.
A stone can be priced two ways, and a jewellery system should support both: a rate per carat or per gram, or a flat value for the stone. Neither of them changes the net weight, which is decided by the stone's weight alone.
Where this goes wrong in practice
- Net weight typed, gross weight assumed. If a system derives net from gross by subtracting a stone weight nobody entered, net silently equals gross and every stone-set piece is overpriced.
- Stone weight recorded as a description. "1 stone approx 6ct" cannot be subtracted by anything, so it is not a weight; it is a note.
- Fine weight taken from gross. Stock then claims to hold metal that is demonstrably stone, and the monthly reconciliation cannot close.
- Purity from the wrong metal. A silver fineness applied to a gold item produces a fine weight that is arithmetically fine and physically nonsense.
What DataJewellers does with these figures
Every item carries gross weight, stone weight and net weight as separate stored figures. Net weight is entered rather than inferred, so a piece with no stones and a piece whose stone weight was never captured are not the same record. Fine weight is derived from net weight and the item's purity, and a purity belonging to another metal cannot be attached to an item — a gold piece takes gold karats, a silver piece takes silver fineness.
The same four figures print on the tag and appear on the invoice, so what the scale said, what the label shows and what the customer is charged are one set of numbers rather than three. Jewellery inventory management describes how those records are kept across branches.
Questions
Is net weight the same as fine weight? No. Net weight is the metal in the piece at whatever purity it is. Fine weight is how much pure metal that represents: net weight times fineness. A 10 g 22K item has a net weight of 10 g and a fine weight of 9.16 g.
Should making charges be calculated on gross or net? On the basis the business agrees with the customer, and it varies by shop — per gram of net weight, a flat amount per piece, or a percentage. What matters is that it is applied consistently and shown on the invoice as its own line rather than folded into the metal price.
What about wastage? Wastage is an agreed percentage applied to the metal, and like making charges it belongs on its own line. It is a commercial term, not a property of the piece, so it does not change any of the four weights.
Related
- Jewellery purityKarats, fineness, and what 916 and 925 mean
- Tracking gold stockReconciling on fine weight
- Jewellery billing softwareHow these figures reach an invoice
- Inventory managementWhere the weights are stored
See the weights on a real item
DataJewellers records gross, stone and net weight for every piece and derives fine weight from net weight and purity.