Is 18KW the same as 18K White?

Yes. 18KW, 18K White, K18WG all denote the same material — 75.0% gold. Different markets and eras stamp it differently, but the purity is identical.

How much is 18KW worth?

Its melt value is the gold spot price × 0.750 × the weight in grams. Buyers then deduct roughly 5–15% for refining and margin, so a quoted buy-back price sits a little below that theoretical figure.

How do I confirm a 18KW stamp is genuine?

Look at the mark under 10× magnification for crisp, even strikes, cross-check the weight-to-volume ratio against the expected density (14.7 g/cm³ for this alloy), scan it with the Jewelry Identifier app, and — when it matters — have an XRF test done by an assay office or gemological lab.

* Gold hallmark

The 18KW hallmark: meaning, purity & value

18KW is 18K white gold (75% Au + white alloys, often rhodium plated). Melt tracks 18K gold, not platinum.

Published May 30, 2026

Quick facts

Metal: Gold
Purity: 75.0%
Fineness: 750/1000
Karat: 18K
Common regions: United States, Japan
Density: 14.7 g/cm³
Standard: ISO 9202

Stamps that mean the same thing

This purity may be struck into jewelry as any of: 18KW / 18K White / K18WG. The mark differs by country and era, but the metal content is identical.

What 18KW tells you

18KW is 18K white gold (75% Au + white alloys, often rhodium plated). Melt tracks 18K gold, not platinum.

How to value it

The melt value of a 18KW piece is gold spot price × 0.750 × weight (g). A buyer typically deducts 5–15% for assay, refining, and margin, so the cash offer lands just under that figure. Stones and complex settings are usually excluded from the metal weight.

Live calculators: gold karat × weight · item × karat estimates · per-gram hub.

How to check it yourself

Examine the stamp under a 10× loupe — genuine marks are crisp and evenly struck, not doubled or smeared.
Confirm the mark reads 18KW or an equivalent such as 18K White.
Weigh the piece and estimate its volume — the density should land near 14.7 g/cm³ for this alloy.
Photograph it in the Jewelry Identifier app to read the metal, hallmark, and any gemstones from the image.
For a binding result, have an assay office or gemological lab run an XRF purity test.

Sources

ISO 9202
Trade hallmark references

* Frequently asked

FAQ

Q. Is 18KW the same as 18K White?: A. Yes. 18KW, 18K White, K18WG all denote the same material — 75.0% gold. Different markets and eras stamp it differently, but the purity is identical.
Q. How much is 18KW worth?: A. Its melt value is the gold spot price × 0.750 × the weight in grams. Buyers then deduct roughly 5–15% for refining and margin, so a quoted buy-back price sits a little below that theoretical figure.
Q. How do I confirm a 18KW stamp is genuine?: A. Look at the mark under 10× magnification for crisp, even strikes, cross-check the weight-to-volume ratio against the expected density (14.7 g/cm³ for this alloy), scan it with the Jewelry Identifier app, and — when it matters — have an XRF test done by an assay office or gemological lab.

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