Blog·Karat & purity
Gold Karat Stamps and Hallmarks: What 585, 750, and 417 Really Mean
A gold calculator only works when your inputs match the metal. The most common mistake is typing the wrong karat because the jewelry shows a number like 585 or 750 instead of “14K” or “18K.” This guide explains how gold purity stamps, hallmarks, and US-style karat stamps relate—so you can cross-check weight, choose the right setting in our gold calculator, and compare offers with confidence.
Why stamps matter more than the scale
Melt value is weight × purity × price per unit for that purity. If purity is off by one tier—say you treat a 585 stamp as 18K—you can overestimate value by a wide margin. That is why dealers test (acid, XRF, density) even when a gold karat stamp is visible: stamps can wear down, be wrong, or apply only to part of the piece.
For planning and negotiation, start with what the mark claims, then treat the result as a baseline until a buyer confirms purity. Our gold karat guide lists how each karat maps to gold percentage; below we focus on how those numbers appear on the metal.
Two naming systems: karat vs millesimal fineness
In the US, people usually say 10K, 14K, 18K, or 22K. Pure gold is 24K (often marked 999 or “24K” depending on region).
In much of Europe and on many imports, you see a three-digit hallmark: the weight of gold in parts per thousand. Examples: 375 = 37.5% gold = 9K (common overseas); 585 = 58.5% = 14K; 750 = 75% = 18K; 916 ≈ 22K; 999 = fine gold.
The math is the same whether the label says “14K” or “585”—only the notation changes. Your gold jewelry stamp is a shorthand for that fraction.
Quick reference: stamps to karat
Use this when translating a hallmark into calculator inputs. Percentages are approximate definitions used in trade; always match the stamp your piece actually carries.
| Fineness stamp | Typical karat | Gold fraction |
|---|---|---|
| 417 | 10K | 41.7% |
| 585 | 14K | 58.5% |
| 750 | 18K | 75.0% |
| 916 | 22K (common in some regions) | 91.6% |
| 999 / 999.9 | 24K / fine | 99.9%+ |
If you see 375, that is often 9K (37.5% gold)—less common in US domestic jewelry but appears on imported items. When in doubt, align your calculator with the exact stamp, not a guess.
Where to look—and what is not a purity stamp
Marks usually sit on clasps, posts, inner ring shanks, or small tags. Use bright light or magnification; older pieces may have faint punches. Some items carry both a fineness number and a maker or assay office mark; for valuation, the fineness or karat number is what maps to purity.
Words like gold plated, GP, GE, or 1/20 14K GF mean the bulk of the item is not solid gold through and through. Standard melt value tools assume solid alloy; plated or filled pieces need a different evaluation—do not plug their full weight in as if it were 14K solid.
Live melt reference by karat (per gram)
Once you know whether your piece is 10K, 14K, 18K, etc., use per-gram melt figures as a reference. These values reflect metal content, not a dealer offer. For buyer ranges, use the scrap gold calculator.
Workflow: stamp → karat → calculator
- Identify the stamp or hallmark (585, 750, “14K,” etc.).
- Convert to the karat option your tool uses—our gold weight converter helps if you only have pennyweight or ounces.
- Weigh the gold parts you are selling (not stones or steel clasps, when separable).
- Run the homepage gold calculator for melt-style value, then compare channels using the scrap tool if you plan to sell.
FAQ
Bottom line: A clear gold karat stamp or 585/750 hallmark tells you which purity tier to use. Match that tier in your calculator, keep weight accurate, and remember that buyers still pay a share of melt—not the full theoretical metal value.