FREE Gold Purity Calculator 2026

Karat, Fineness, Hallmarks: What Your Gold’s Stamp Actually Means

Purity is the multiplier that decides whether two same-weight pieces are worth the same or half as much. A 10-gram 24K bangle holds roughly 2.4 times the gold of a 10-gram 10K ring. The tool above converts between every purity system — karat, percentage, and fineness — so a stamp you don’t recognize becomes a number you can use.

Karat: Parts Out of 24

The karat system divides gold purity into 24 parts. 24K is 24 out of 24 — pure gold. 14K is 14 out of 24, or 58.3%. The math is just division, but the reason for the system is metallurgy: pure gold is too soft for daily wear, so it’s alloyed with copper, silver, nickel, or zinc for strength. The karat tells you how much of the alloy is actually gold.

The purities you’ll actually encounter in the United States:

• 24K (99.9%) — effectively pure. Too soft for most jewelry; standard for bullion bars and many bullion coins. Stamped 999 or 24K.
• 22K (91.7%) — common in South Asian and Middle Eastern jewelry; durable enough for daily wear. Stamped 916 or 22K.
• 18K (75%) — the luxury-jewelry standard in the US and Europe. Good balance of color, purity, and durability. Stamped 750 or 18K.
• 14K (58.3%) — the workhorse of American jewelry: engagement rings, wedding bands, chains. Stamped 585 or 14K.
• 10K (41.7%) — the legal minimum to be sold as gold in the United States under FTC rules. Common in affordable jewelry and class rings. Stamped 417 or 10K.

Fineness: The Millesimal Stamps

Many pieces — especially imported ones — skip karats entirely and stamp fineness: parts of pure gold per thousand. 750 means 750/1000 pure, i.e., 18K. 585 is 14K. 417 is 10K. 916 is 22K. 999 is 24K (it’s 999 rather than 1000 because refining to literal 100.0% is impractical; 999 fine is the commercial definition of pure).

If your piece is stamped 585 and the calculator asks for karat, they’re the same answer: 14K. The converter above moves between these systems in either direction.

How Buyers Verify Purity (and How You Can Too)

A stamp is a claim, not proof — counterfeits and mis-stamps exist. Here’s how the trade actually checks:

Acid test. The classic jeweler’s method: a tiny scratch on a test stone, a drop of acid calibrated to a karat level. If the mark survives the 14K acid, the piece is at least 14K. Cheap, fast, slightly destructive (invisible on a worn edge, but still a scratch).

Electronic tester. A probe measures the metal’s conductivity against known standards. Non-destructive and quick; most reputable buyers will test in front of you.

XRF (X-ray fluorescence). The lab-grade option. It reads the exact elemental composition without touching the piece. Refineries use it; some high-end buyers have handheld units.

What you can do at home: start with a magnet (gold isn’t magnetic — if it sticks strongly, something’s wrong), check the stamp with a loupe, and compare heft against a known piece. Our guide to testing gold at home walks through the full sequence. For a sale, though, let the buyer test in front of you and watch the result — a legitimate buyer has nothing to hide.

Using the Purity Tool

Enter what you know — a karat number, a fineness stamp, or a percentage — and the tool gives you the other two plus the pure-gold multiplier used in valuation math. Then take that multiplier to the main gold calculator with your weight and today’s live price. For a full explanation of each mark, see our gold purity chart.

What the Alloy Metals Do (and Why Color Varies)

The non-gold metals in the alloy aren’t filler — they determine color, hardness, and workability:

• Yellow gold is alloyed with silver and copper in balanced proportions. More copper shifts it toward rose; more silver toward pale yellow.
• White gold uses nickel or palladium as the whitening alloy, then usually gets rhodium plating for a bright finish. Nickel white gold is harder; palladium white gold is hypoallergenic but pricier.
• Rose gold is copper-heavy — 18K rose is 75% gold, 25% copper, essentially.

None of this changes melt value: 14K rose, 14K white, and 14K yellow all hold 58.3% gold. But it explains why two 14K pieces look nothing alike, and why a buyer testing with acid needs to know the alloy family — white gold’s nickel content can behave differently under quick tests.

Plated, Filled, Vermeil — Not the Same as Solid

Purity tools and melt math assume solid karat gold. Three common impostors:

• Gold plated (GP, HGE, RGP stamps): a microscopic gold layer over base metal — often less than 0.1% gold by weight. Melt value: effectively zero. Our guide on gold-plated jewelry explains the stamps.
• Gold filled (GF, “1/20 14K GF”): a thick mechanically-bonded gold layer, legally at least 5% gold by weight. Worth a small fraction of solid gold’s melt value — see our gold filled value guide.
• Vermeil: gold-plated sterling silver. The silver has some value; the gold layer doesn’t move the needle.

If your piece is stamped GP, EP, HGE, or RGP, don’t run it through a melt calculator expecting a number — there isn’t one. If it’s stamped “1/20 14K GF,” it’s gold filled and needs the filled-valuation method, not the solid-karat math.

Frequently Asked Questions

What does 585 stamped on my ring mean?

585 is the fineness mark for 14K gold — 58.5% pure gold (the trade rounds 58.33% up in the stamp). It’s the most common stamp on American gold jewelry. Enter 585 in the tool above and you’ll get 14K / 58.3% back.

Is 10K gold “real” gold?

Yes. 10K is 41.7% pure gold, and it’s the minimum karat that US law allows to be marketed as gold. It’s harder and more scratch-resistant than higher karats, which is why it’s popular for class rings and men’s bands. Anything below 10K can’t legally be called gold in the US.

Why is 24K stamped 999 instead of 1000?

Because absolute 100.0% purity isn’t commercially achievable — refining tops out around 99.99%. The industry settled on 999 fine (“three nines”) as the definition of pure gold for bars and bullion. For valuation purposes, treat 999 as 100%.

Can white gold be 14K or 18K too?

Yes — karat measures gold content, not color. White gold is yellow gold alloyed with white metals (nickel or palladium) and usually rhodium-plated. A 14K white gold ring and a 14K yellow gold ring hold exactly the same amount of pure gold and have the same melt value.

My jewelry has no stamp — what karat should I assume?

Assume nothing. Unstamped gold is common in older pieces, handmade jewelry, and some imported items. Don’t guess a karat for a valuation — have it tested. Guessing 14K on a 10K piece overstates value by 40%; guessing 10K on an 18K piece leaves money on the table.