Numeric gold hallmarks such as 375, 417, 585, 750, 916 and 999 express millesimal fineness — gold content in parts per thousand (‰). A 585 hallmark means 58.5% gold, 750 means 75.0% gold, and 999 means 99.9% gold. Karat and fineness are related purity systems, but common hallmark-to-karat associations are not always mathematically identical. Use the Hallmark Lookup Tool to identify a specific marking on your gold item.
This guide explains what each of the six most common numeric gold hallmarks means, how fineness converts to gold percentage, where karat and fineness values diverge, and how purity marks differ from maker marks and filled or plated markings.
What a Numeric Gold Hallmark Means
A numeric gold hallmark indicates the item’s gold content using millesimal fineness — a system that expresses purity in parts per thousand. The conversion to gold percentage is direct:
Gold Percentage = Fineness ÷ 10
Purity Decimal = Fineness ÷ 1000
For example, a hallmark of 750 means 750 parts per thousand, or 75.0% gold by weight. The remaining 25.0% consists of alloying metals such as silver, copper, zinc, or nickel that increase hardness and durability.
Each fineness value has a common karat association, but karat and fineness are distinct systems. The approximate karat equivalent of any fineness number is:
Approximate Karat = 24 × (Fineness ÷ 1000)
This is a mathematical conversion only, not a substitute for jurisdiction-specific hallmark rules. The sections below cover each common hallmark individually.
Gold Hallmark 375
A 375 hallmark indicates 37.5% gold content (375 parts per thousand). The common karat association is 9K gold.
| Attribute | Value |
|---|---|
| Fineness | 375 ‰ |
| Gold Percentage | 37.5% |
| Common Karat | 9K |
| Karat Fraction | 9/24 = 0.375 |
In this case, the karat fraction 9/24 = 0.375 matches the fineness exactly. 375 gold is common in the United Kingdom and other markets where 9K is a legal standard for gold jewelry. The majority of the item by weight (62.5%) is alloy metal.
Gold Hallmark 417
A 417 hallmark indicates 41.7% gold content (417 parts per thousand). The common karat association is 10K gold.
| Attribute | Value |
|---|---|
| Fineness | 417 ‰ |
| Gold Percentage | 41.7% |
| Common Karat | 10K |
| Exact Karat Fraction | 10/24 ≈ 41.667% |
The exact karat fraction 10/24 produces 41.667%, while the 417 fineness stamp represents 41.7%. The difference is small (0.033 percentage points) but the two values are not mathematically identical. 10K was historically treated as a minimum threshold in older U.S. Jewelry Guides, but the FTC removed that 10-karat threshold in its 2018 revisions. Gold content should be described accurately with its karat fineness. For value calculations based on 10K gold, see the 10K Gold Calculator.
Gold Hallmark 585
A 585 hallmark indicates 58.5% gold content (585 parts per thousand). The common karat association is 14K gold.
| Attribute | Value |
|---|---|
| Fineness | 585 ‰ |
| Gold Percentage | 58.5% |
| Common Karat | 14K |
| Exact Karat Fraction | 14/24 ≈ 58.333% |
The exact karat fraction 14/24 equals 58.333…%, while the 585 fineness stamp represents 58.5%. The difference is 0.167 percentage points. 14K gold is one of the most common purities for jewelry worldwide, offering a balance between gold content and durability. For 14K-specific calculations, see the 14K Gold Calculator.
Gold Hallmark 750
A 750 hallmark indicates 75.0% gold content (750 parts per thousand). The common karat association is 18K gold.
| Attribute | Value |
|---|---|
| Fineness | 750 ‰ |
| Gold Percentage | 75.0% |
| Common Karat | 18K |
| Karat Fraction | 18/24 = 0.750 |
Unlike 585 and 417, the 750 fineness and 18K karat fraction are an exact match: 18/24 = 0.750 = 75.0%. 18K gold is widely used in fine jewelry markets across Europe, Asia, and the Middle East. For 18K value calculations, see the 18K Gold Calculator.
Gold Hallmark 916
A 916 hallmark indicates 91.6% gold content (916 parts per thousand). The common karat association is 22K gold.
| Attribute | Value |
|---|---|
| Fineness | 916 ‰ |
| Gold Percentage | 91.6% |
| Common Karat | 22K |
| Exact Karat Fraction | 22/24 ≈ 91.667% |
The exact karat fraction 22/24 equals 91.667%, while the 916 fineness stamp represents 91.6%. The difference is 0.067 percentage points. 22K gold is common in South Asian, Middle Eastern, and African jewelry traditions, where high gold content is preferred. For 22K and 24K value calculations, see the 22K–24K Gold Calculator.
Gold Hallmark 999
A 999 hallmark indicates 99.9% gold content (999 parts per thousand). The common karat association is 24K gold — the highest standard purity used in commercial gold products.
| Attribute | Value |
|---|---|
| Fineness | 999 ‰ |
| Gold Percentage | 99.9% |
| Common Karat | 24K |
| Karat Fraction | 24/24 = 1.000 |
The mathematical karat fraction 24/24 = 100%, while the 999 fineness acknowledges that absolute 100.0% purity is not achievable in practice. Some investment-grade bullion carries a 9999 (99.99%) fineness mark, indicating even higher refining precision. 999 gold is soft and is used primarily in bullion bars, bullion coins, and specific high-purity jewelry.
Karat vs Fineness
Karat and fineness are two systems for expressing gold purity. Karat divides pure gold into 24 parts, while millesimal fineness uses parts per thousand.
| Fineness | Gold % | Exact Karat Fraction | Exact Karat % | Difference |
|---|---|---|---|---|
| 375 | 37.5% | 9/24 = 0.375 | 37.500% | 0.000 |
| 417 | 41.7% | 10/24 ≈ 0.41667 | 41.667% | 0.033 |
| 585 | 58.5% | 14/24 ≈ 0.58333 | 58.333% | 0.167 |
| 750 | 75.0% | 18/24 = 0.750 | 75.000% | 0.000 |
| 916 | 91.6% | 22/24 ≈ 0.91667 | 91.667% | 0.067 |
| 999 | 99.9% | 24/24 = 1.000 | 100.000% | 0.100 |
Some hallmark-karat pairs (375/9K and 750/18K) are exact matches. Others (585/14K and 916/22K) are close but not identical. The difference matters when precise purity calculations are needed — for example, when calculating scrap gold value.
Can a Hallmark Prove an Item Is Gold?
No. A hallmark is evidence of the manufacturer’s or assay office’s declaration of gold content, but a stamped number alone cannot guarantee authenticity. Hallmarks can be worn and difficult to read, applied incorrectly, or present on counterfeit items.
Reasons a hallmark may not reflect the actual gold content:
- Worn or damaged marks — Decades of wear can make numbers partially illegible.
- Multiple marks — An item may carry a purity mark, a maker mark, a date letter, and an assay office mark. Only the numeric fineness or karat stamp indicates gold content.
- Jurisdiction differences — Hallmarking standards, required marks, and enforcement vary by country. A mark that is mandatory in one jurisdiction may be voluntary in another.
- Counterfeit stamps — A fake or misleading hallmark can appear on non-gold or lower-purity items.
Professional testing — acid testing, electronic testing, X-ray fluorescence (XRF), or a formal assay — provides more reliable purity verification than a visual stamp inspection alone. For help interpreting a specific mark, use the Hallmark Lookup Tool.
How Filled and Plated Marks Differ
Not every gold marking indicates solid gold. Gold-filled and gold-plated items use different marking conventions, and confusing them with solid-gold hallmarks can lead to significant valuation errors.
Gold-filled (GF) markings such as 1/20 12K GF combine a layer ratio with the karat of the gold alloy layer. The 1/20 describes the weight relationship of the gold layer to the total item, and 12K describes the purity of that layer. The fine-gold fraction is the layer ratio multiplied by the layer purity:
1/20 × 12/24 = 0.025
This equals approximately 2.5% fine gold by total item weight — not “5% pure gold.” For gold-filled value calculations, see the Gold-Filled Calculator.
Gold-plated (GP, GEP, HGP) items have a much thinner gold layer than gold-filled items. The gold content is typically too small to recover economically.
Solid gold items carry fineness stamps (375, 585, 750, etc.) or karat stamps (9K, 14K, 18K, etc.) without filled or plated qualifiers.
Frequently Asked Questions
Is 585 exactly the same as 14K?
No. The 585 fineness mark means 58.5% gold. The exact karat fraction for 14K is 14/24 ≈ 58.333%. The two values are commonly associated but differ by 0.167 percentage points.
Is 916 exactly the same as 22K?
No. The 916 fineness mark means 91.6% gold. The exact karat fraction for 22K is 22/24 ≈ 91.667%. The two values are commonly associated but differ by 0.067 percentage points.
What does 999 mean?
A 999 hallmark means the item contains 99.9% gold (999 parts per thousand). This is the standard fineness for investment-grade gold bullion and high-purity gold products. Some refined gold carries a 9999 (99.99%) mark indicating even higher purity.
What does 375 mean?
A 375 hallmark means the item contains 37.5% gold (375 parts per thousand), commonly associated with 9K gold. The karat fraction 9/24 = 0.375, so 375 and 9K are an exact mathematical match.
Can a fake gold item have a hallmark?
Yes. A stamped hallmark number can appear on counterfeit or misrepresented items. A hallmark is a declaration, not a guarantee. Professional testing methods such as acid testing, electronic testing, or X-ray fluorescence (XRF) provide more reliable verification of actual gold content.
Sources & Methodology
- Federal Trade Commission (FTC): Guides for the Jewelry, Precious Metals, and Pewter Industries (16 CFR Part 23). Governs fineness marking standards, disclosure requirements, and elimination of the prior 10K threshold in 2018.
- National Institute of Standards and Technology (NIST): Office of Weights and Measures precious metals conversion information (troy ounce, gram, and pennyweight conversions).
- Calculation Methodology: Detailed formula definitions, unit standards, and calculation limitations are documented in our central Calculation & Editorial Methodology.
Gold hallmarks indicate the manufacturer’s or assay office’s declared gold content. A hallmark alone does not guarantee purity or authenticity. For professional-grade purity verification, consult a certified assayer. Once purity is confirmed, use the Scrap Gold Calculator to calculate the item’s value based on live spot prices.