10K, 14K or 18K gold: what's the difference in value?

Two gold-coloured pieces, the same weight on the scale — and yet very different values. The reason is a tiny engraving: the karat. Here is what 10K, 14K and 18K actually change when it comes time to have your jewellery evaluated.

Karat: a proportion, not a grade

Karat is not a quality score: it is the proportion of pure gold in the alloy, expressed on a 24-point scale. The higher the number, the more fine gold the alloy contains. An 18K piece contains considerably more gold than a 10K piece of the same weight.

The rest of the alloy is made up of other metals, which add hardness and sometimes colour: that is what makes white gold and rose gold possible — both contain genuine gold just like yellow gold.

What it changes for the value

A jewellery item's metal value follows simple logic: today's rate × gold proportion × weight. At equal weight, an 18K chain is therefore worth roughly one and a half times a 10K chain, simply because it contains more fine gold.

That is why comparing two pieces "by weight" without knowing their karat is meaningless. To run the math with your own numbers, use our calculator: it gives you the market value of the metal based on purity and weight.

How to identify your jewellery's karat

In most cases, the karat is engraved on the piece: 10K or 417, 14K or 585, 18K or 750. Look inside a ring's band, near a chain's clasp, or on an earring's post.

A hallmark can however be worn, missing or, more rarely, inaccurate. Our article How to tell if gold is real at home explains how to read these markings and why only professional testing confirms actual purity.

Why 10K should not be dismissed

Many people assume their 10K jewellery is "worth nothing". That is wrong: 10K is the most common alloy in North America, and a collection of 10K pieces accumulated over the years can add up to surprising weight — and value. Gold is bought for its metal content, regardless of whether the piece is outdated or damaged.

Karat is not everything: weight matters just as much

A small 18K ring can be worth less than a heavy 10K bracelet. Purity sets the value per gram; weight sets how many grams you have. The two multiply — it is the combination that counts.

The only way to know both numbers precisely for your jewellery is a professional evaluation: exact weighing and purity verification, done in front of you. At On Achète Or, the evaluation is free, without obligation, and each item is calculated separately — you see the value of every piece before deciding anything.