When someone looks at a box of jewellery they're about to sell, the first question is often: "Is this 18K or 14K?" The assumption is that a higher karat automatically means a better price. That's partly true — but only partly.
In reality, weight matters just as much as purity. A thick 14K chain can bring in significantly more than a thin 18K ring. In this guide, we walk through the exact calculation you can use to estimate the value of your own jewellery before selling.
What does karat mean?
Karat (K) tells you what share of a piece's weight is pure gold. The scale runs downward from 24 — 24K is almost pure gold, while lower-karat pieces are made up partly of other metals, usually silver, copper or zinc.
| Karat | Gold content | Common use |
|---|---|---|
| 24K | 99.9% | Investment bars and coins |
| 18K | 75.0% | Luxury jewellery, Europe |
| 14K | 58.5% | Everyday jewellery, North America |
| 9K | 37.5% | More affordable jewellery, UK |
Finnish jewellery is most commonly stamped 750 (= 18K), 585 (= 14K) or 375 (= 9K). The number gives the gold content in thousandths — 750 means 750/1000, i.e. 75%.
How is the sale price calculated?
When gold is bought — including here at Gold Lab — the price is always based on the amount of pure gold in grams, not the total weight of the piece. The formula is simple:
This amount of pure gold is then multiplied by the London spot price, from which the service fee and refining fee are deducted. So the karat directly affects the price — but it's only one variable in the formula.
Why doesn't 18K always mean more money?
Here's the heart of the misconception: the karat tells you the purity percentage, not how many grams of pure gold the piece actually contains. That also depends on the weight of the piece.
In this example, the 14K chain brings in more than twice as much as the 18K ring, simply because the chain contains more metal.
Weight × karat is the number that decides.
When does 18K bring in more?
18K brings in more when the pieces being compared weigh the same. If you have two pieces of equal weight, one 18K and one 14K, the 18K piece is worth more, because it contains more pure gold per gram.
In practice, though, this situation is rare. Jewellery weight varies enormously by type, era and maker:
- Chains and bracelets are often heavier and are commonly 14K
- Rings vary widely — heirloom rings can be light or heavy
- Pendants are often light regardless of karat
- Coins and bars are almost always 24K or 22K
Other factors that don't affect the price
When selling gold, it helps to know what isn't included in the calculation:
- Design or brand doesn't affect the melt value — a Cartier ring and an unbranded ring bring in the same amount if the weight and karat are equal
- Stones and pearls are removed before assessment, and you aren't paid gold prices for them
- Condition doesn't matter, so scratches, dents or a broken clasp don't lower the price, because the gold is melted down regardless
- Gold plating isn't sellable gold, because a thin layer of gold over a steel or silver base doesn't contain a meaningful amount of gold
How to calculate it yourself before selling
You need two things: the piece's weight and its karat. Weight you can get from a kitchen scale; karat from the piece's hallmark.
- Weigh the piece (g)
- Multiply by the gold content: 18K → × 0.750 / 14K → × 0.585 / 9K → × 0.375
- Multiply the result by the spot price (€/g) — you can see it live on our homepage
- The result is the piece's gross potential before service fees
You can also use Gold Lab's calculator directly, which does the math for you and shows an exact offer including service fees.