Jewelry Tips & Advice
Gold Purity Guide: 10K, 14K, 18K and 24K Explained
Gold purity confuses buyers because the number in front of the K is not a quality score. 24K is the purest gold you can buy, and no grading laboratory ranks one karat above another — the karat tells you how much gold is in the alloy, and that is all it tells you.
What makes the mark genuinely useful is the second half of the story: US law attaches specific obligations to it. A correctly marked piece states its gold content, carries a maker’s mark, and tells you whether it is solid or a coating. A badly marked piece tells you nothing you can rely on.
This guide covers what a karat measures, what a seller is required to disclose, what the mark does not cover, and how to use all of it when you choose a piece. It deals with solid gold alloys; for sterling silver and general metal care, see our jewelry metals guide.
What a Gold Karat Actually Measures
A karat is a measure of fineness — the proportion of pure gold in a gold alloy.
Pure gold is the reference point. The FTC’s Jewelry Guides, which govern how gold may be described in the United States, treat 24 karat as “fine” gold: the unalloyed metal. Using the word “Gold” without qualification to describe anything that is not composed throughout of fine gold is treated as misleading. So the karat number is not a badge of quality. It is a statement of how much of the metal is gold.
Karat purity table
| Mark | Pure gold | Other metals |
|---|---|---|
| 24K | fine gold — the unalloyed metal | none |
| 18K | 75.0% | 25.0% |
| 14K | 58.3% | 41.7% |
| 10K | 41.7% | 58.3% |
A gram of 18K gold contains more gold than a gram of 14K, and more again than a gram of 10K. That follows directly from the proportions above, and it is the most useful thing to know when you are comparing two pieces of similar weight.
What the number does not rank
It is worth being precise here, because most buying advice is not.
The FTC Guides set the legal framework for purity claims. They do not rank karats by wear resistance, and no grading laboratory issues a durability grade for gold. A claim that 10K is “better” than 18K, or the reverse, is an expression of preference rather than a measurement.
What you can rely on are the proportions in the table above, the disclosure obligations set out below, and your own answer to a simple question: what will this piece be asked to survive?
What the Law Requires When Gold Is Marked
This is the part that protects you, and the part most product listings get wrong.
The word “Gold” on its own is a claim of 24 karats. The Guides treat the unqualified use of “Gold” to describe a product that is not composed throughout of fine gold as misleading. “Gold Ring”, describing a 14K ring, is therefore not a correct description — the karat has to come first.
A correct mark puts the karat immediately before the word. The Guides give the acceptable forms as “14 Karat Gold”, “14 K. Gold” or “14 Kt. Gold”, and require the fineness designation to be at least as conspicuous as the word “Gold”. A piece may also carry the karat alone — “14 Karat”, “14Kt.”, “14 K.” — without the word “Gold” at all.
Hollow pieces may not be called solid. Where a product is composed throughout of gold alloy but contains a hollow centre, the Guides require that fact to be disclosed alongside the word “Gold”, and state that such products should not be marked or described as solid. “Solid 14Kt. Gold” on a hollow piece is not a correct description.
A quality mark must be traceable. The National Stamping Act requires any manufacturer or dealer who applies a quality mark indicating gold or silver to also apply their trademark or name to the article (15 U.S.C. §297). A correctly marked piece therefore usually carries two things — the karat, and a maker’s mark. A karat with no maker behind it is a mark nobody has taken responsibility for.
The mark carries a legal tolerance. Actual fineness may fall short of the marked fineness by no more than three parts per thousand; where the assay includes solder, the permitted deviation is seven parts per thousand (15 U.S.C. §295). A “14K” mark therefore does not promise exactly 58.3%. It promises a fineness within a defined legal tolerance of it — which is why a small shortfall is not automatically a misdescription, while a large one is.
What a Karat Mark Does Not Cover
A karat number applies to a solid gold alloy. It is not used for coatings, and the same Guides set separate terms for those, each with its own minimum fineness and minimum thickness. If a piece is not solid gold, the karat number is not the mark you should be reading.
| Term | What it requires |
|---|---|
| Gold Plate, Gold Plated, Gold Overlay, Rolled Gold Plate | A gold alloy plating of at least 10 karat fineness on all significant surfaces |
| Gold Filled | The same, where the plating is at least 1/20th of the weight of the metal in the article; Gold Overlay and Rolled Gold Plate may be used at 1/40th |
| Gold Electroplate | Electroplated gold or gold alloy of at least 10 karat fineness, at a minimum thickness equivalent to 0.175 microns of fine gold; “Heavy Gold Electroplate” at 2.5 microns |
| Vermeil | A sterling silver base coated with gold or gold alloy of at least 10 karat fineness, at a minimum thickness equivalent to 2.5 microns of fine gold |
Rhodium must be disclosed. Many pieces — white gold in particular — carry a surface layer of rhodium. The Guides make it unfair or deceptive to fail to disclose a surface-layer application of rhodium on a product described as precious metal. If a listing calls a piece white gold and says nothing about rhodium, that omission is worth asking about.
Which Karat Should You Choose?
The Guides do not decide this for you, so here is how to decide it yourself.
Start with gold content, not perceived quality. If more gold per gram is what you want, the higher karat delivers it. That is the only thing the karat number itself settles.
Then ask what the piece has to survive. A piece worn daily through work, sport and sleep meets more contact than one worn occasionally. The answer to that question is yours, not the mark’s — and it is the one input no purity table can supply.
Then look at the piece’s construction. Band thickness, whether the piece is hollow, and how the setting is built all describe the object in front of you in a way the karat number does not. A hollow piece is a different object from a solid one at the same karat, and the Guides require that difference to be disclosed. How that plays out on a specific setting is worth seeing in context — the Asscher-cut moissanite buying guide walks through the same trade-off for a stone with four exposed corners.
And check what you are actually being told. A listing that gives a karat but no maker’s mark, or that calls a hollow piece “solid”, or that says only “gold” with no karat number, is not giving you the information the Guides require. That is a useful signal whichever karat you were leaning towards.
14K sits in the middle of the range, and the easiest way to judge the differences is against real pieces: browse the Engagement & Wedding Ring collection or the moissanite rings.
Buying Gold in the Trade: What to Specify
For OEM, ODM, private-label and wholesale orders, the karat is a specification item, and ambiguity in it is paid for in rejected units.
Put these in writing:
- the karat, expressed with the number immediately before the word “gold” in any customer-facing description
- whether the piece is solid or hollow, and if hollow, that the description says so
- your marking requirement — karat plus your trademark or name, as the National Stamping Act requires of the party applying the mark
- the alloy mix, if the piece has to match an existing line
- the accepted deviation from the stated fineness, measured against the statutory tolerances above
- whether any rhodium finish is applied, and that it is disclosed on the listing if it is
The last two are the ones buyers most often leave out, and they are the two that turn into disputes — one about a piece that assays slightly under its mark, the other about a finish that was never mentioned.
Our own production uses solid 10K, 14K and 18K gold and S925 sterling silver, across our moissanite rings and our other lines.
Frequently Asked Questions
What does 14K gold mean?
14K means the alloy contains 14 parts pure gold out of 24 — 58.3% — with the remaining 41.7% made up of other metals. Under the FTC Jewelry Guides the karat designation must appear immediately before the word “Gold” and be at least as conspicuous as it.
Is 24K gold pure gold?
The Guides treat 24 karat as “fine” gold, the unalloyed metal. It is the reference point the whole karat system measures against, and using the word “Gold” without qualification on anything else is treated as misleading.
Is 18K better than 14K?
Not in any way the Guides or a laboratory recognises. 18K contains more gold per gram — 75% against 58.3% — and that is the whole of what the number tells you. No grading body issues durability grades for gold, so a “better” or “harder” claim is a preference rather than a measurement.
Can a hollow piece be sold as solid gold?
No. Where a piece is gold alloy with a hollow centre, the Guides require that to be disclosed and state it should not be described as “solid”. “Solid 14Kt. Gold” on a hollow piece is not a correct description.
Does a 14K mark guarantee exactly 58.3% gold?
No. The National Stamping Act permits the actual fineness to fall short of the marked fineness by up to three parts per thousand, or seven parts per thousand where the assay includes solder. The mark is a fineness claim within a statutory tolerance, not a precise assay.
Sources
Every factual claim in this guide is drawn from the sources below. Where no authoritative source could be found, the claim was left out rather than softened.
- FTC Jewelry Guides, 16 CFR Part 23 — “Guides for the Jewelry, Precious Metals, and Pewter Industries” (Federal Trade Commission; current eCFR text, source 83 FR 40667, 16 August 2018):
- § 23.3(a) and (b)(1)–(2): that misrepresenting gold content is deceptive, and that unqualified use of “Gold” on anything not composed throughout of fine (24 karat) gold, or on a lower-karat alloy without a karat fineness designation immediately preceding it, is misleading.
- § 23.3(c)(1): the acceptable markings “14 Karat Gold”, “14 K. Gold”, “14 Kt. Gold” and the karat-only forms; the rule that the fineness designation be of equal conspicuousness; and the hollow-centre provision — disclosure required, and the product should not be marked or described as solid.
- § 23.3(c)(2)–(3): the definitions and minimum fineness of Gold Plate, Gold Plated, Gold Overlay, Rolled Gold Plate and Gold Filled; the 1/40th and 1/20th weight-ratio thresholds; and the 0.175-micron and 2.5-micron minimum thicknesses for Gold Electroplate and Heavy Gold Electroplate.
- § 23.3 footnote 32: the National Stamping Act tolerances of three parts per thousand, and seven parts per thousand where the part tested contains solder.
- § 23.4(b): the definition of “vermeil” as a sterling silver base coated with gold or gold alloy of at least 10 karat fineness at a minimum thickness equivalent to 2.5 microns of fine gold.
- § 23.7: that failing to disclose a surface-layer application of rhodium on a product marked or described as precious metal is unfair or deceptive.
- § 23.10: the definition of a “quality mark”, the legibility requirement, and — citing the National Stamping Act, 15 U.S.C. §297 — the requirement that a person applying a quality mark indicating gold or silver apply their trademark or name to the article.
- National Stamping Act (Jewelers’ Liability Act), 15 U.S.C. §295 — standard of fineness of gold articles and permitted deviation: not less than three one-thousandth parts below the marked fineness, and seven one-thousandth parts for the entire article including solder.
- National Stamping Act, 15 U.S.C. §297 — disclosure of the identity of manufacturers, processors or distributors on articles bearing a quality mark.
- National Stamping Act, 15 U.S.C. §294 — prohibition on falsely marked gold and silver ware in import, export and interstate commerce.
Derived rather than quoted: the percentage figures in the purity table (75.0%, 58.3%, 41.7%) are the arithmetic of the karat proportion against the 24-karat standard the Guides use — 18/24, 14/24 and 10/24. The Guides define the karat system and treat 24 karat as fine gold; they do not print the percentages themselves.
Deliberately omitted, because no authoritative source was found: any ranking of the karats by hardness, wear resistance or suitability for daily wear. Every source offering such a ranking was a retailer or an opinion piece rather than GIA, IGI or the FTC, so the guide states the proportions and the legal obligations and leaves the wear judgement to the buyer.
Specific figures for Lentisara’s capacity, order terms, lead times and prices are absent because they were not verified for publication.
