Gold Fineness Explained: What 750, 585, and 375 Actually Mean

Published: January 28, 2026

When examining jewelry marks, you'll encounter numbers like 750, 585, or 375 stamped near hallmarks and maker's marks. These aren't random—they're fineness marks indicating the precise gold content of the metal. Understanding fineness unlocks one of the most reliable authentication markers on any piece.

Here's how to read these numbers, convert between systems, and understand what they reveal about your jewelry.

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What Fineness Means

Fineness expresses metal purity in parts per thousand. A fineness of 750 means the alloy contains 750 parts gold per 1,000 parts total—or 75% pure gold.

This system eliminates ambiguity. While "18 karat" means different things in different contexts (and has been historically inconsistent), 750 fineness is mathematically precise: 75% gold, period.

The formula:

Fineness = (Pure Gold Content ÷ Total Metal Weight) × 1000

For 18K gold: (18 ÷ 24) × 1000 = 750

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Karat vs Fineness: Two Systems, Same Information

Karat system divides gold into 24 parts. Pure gold is 24 karat. An 18-karat piece contains 18 parts gold and 6 parts other metals.

Fineness system uses parts per thousand. Pure gold is 999 (or 1000). An 18-karat piece has fineness 750.

Both describe the same thing differently:

Karat	Fineness	Gold Content
24K	999/1000	99.9%
22K	916	91.6%
18K	750	75.0%
14K	585	58.5%
10K	417	41.7%
9K	375	37.5%

Why fineness won? International trade needed standardization. The Vienna Convention on Precious Metal Hallmarking adopted fineness as the universal language—750 means the same in London, Paris, Milan, and Geneva.

Our precious metals converter handles conversions automatically, and the calculator helps with related measurements.

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Common Gold Fineness Marks

750 — 18 Karat Gold

The international standard for fine jewelry. Contains 75% gold with 25% alloying metals (typically copper, silver, zinc, or palladium depending on color).

Where you'll see it:

• European fine jewelry (standard requirement in many countries)
• High-end American brands
• Asian jewelry markets (alongside karat marks)
• Virtually all signed luxury jewelry

Authentication note: 750 is the most common fineness for pieces from Cartier, Van Cleef & Arpels, Bulgari, and other major houses. If a supposedly high-end piece is marked 585 or lower, that's worth questioning.

585 — 14 Karat Gold

Common in American jewelry, less common in European fine jewelry. Contains 58.5% gold.

Where you'll see it:

• American-made pieces (historically popular for balance of durability and gold content)
• Some branded jewelry from US manufacturers
• Less common on European luxury brands

Authentication note: Legitimate 14K/585 pieces exist from major brands, but European luxury houses predominantly use 750. A "Cartier" piece marked 585 warrants careful examination.

375 — 9 Karat Gold

The minimum legal standard for gold in the UK. Contains 37.5% gold.

Where you'll see it:

• British jewelry (legal minimum since 1854)
• Some commercial-grade international pieces
• Rarely on luxury branded jewelry

Authentication note: Major luxury houses don't typically produce 9K pieces. A "Van Cleef" marked 375 would be highly suspicious.

916 — 22 Karat Gold

High-purity gold common in Indian, Middle Eastern, and Asian jewelry. Contains 91.6% gold.

Where you'll see it:

• Traditional Indian/South Asian gold jewelry
• Middle Eastern gold markets
• Some high-end Asian pieces
• Bullion-style jewelry

999 — 24 Karat / Pure Gold

Near-pure gold (99.9%). Too soft for most jewelry; used primarily for bullion, special commemorative pieces, and certain traditional Asian jewelry.

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Platinum Fineness

Platinum uses the same fineness system:

Fineness	Platinum Content
950	95% platinum
900	90% platinum
850	85% platinum

950 is the standard for fine jewelry platinum. Major brands—Harry Winston, Van Cleef & Arpels, Cartier—use 950 platinum. Lower finenesses exist but are less common in the luxury market.

Authentication note: "PLAT" without a fineness number is common on American pieces (assumes 950). "Pt950" or "950" confirms platinum content. European pieces typically show the fineness explicitly.

See our platinum hallmarks guide for mark-specific details.

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Silver Fineness

Silver fineness works identically:

Fineness	Name	Silver Content
999	Fine silver	99.9%
958	Britannia	95.8%
925	Sterling	92.5%
900	Coin silver	90.0%
800	Continental	80.0%

925 (Sterling) is the standard for fine silver jewelry and objects. Lower finenesses (800, 830) appear on continental European silver.

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Reading Fineness Marks on Jewelry

Fineness marks typically appear:

Near other hallmarks: As part of the mark "stack" on clasps, inside rings, on catch plates.

Standalone: Sometimes just the number appears without accompanying hallmarks (especially on US pieces, which don't require assay office hallmarks).

With purity symbols: UK silver shows the lion passant alongside 925; platinum shows the orb alongside 950.

What to look for:

• Clear, crisp stamp impression
• Consistent style with other marks on the piece
• Appropriate fineness for the brand and era
• Logical placement (near maker's marks, in standard locations)

Red flags:

• Fineness mark without expected accompanying hallmarks
• Mismatched style (modern-looking fineness stamp on "antique" piece)
• Unusual fineness for the claimed brand/market
• Poorly struck or unclear marks

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Why Fineness Marks Matter for Authentication

Fineness marks provide testable claims. A piece marked 750 should test as 75% gold. Modern XRF testing can verify this non-destructively. Acid testing provides another verification method.

When marks and tests don't match:

• The piece may be counterfeit (marked to appear more valuable)
• Marks may have been added later
• The piece may have been repaired with different-content metal
• Surface plating may skew surface testing

When marks and tests do match: This confirms the metal content but doesn't prove brand authenticity. A fake "Cartier" can still be made from real 750 gold. Fineness verification is one piece of evidence, not the whole picture.

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International Variations

Different markets have different expectations:

United States: Karat stamps (14K, 18K) more common than fineness. No mandatory hallmarking—marks are self-applied by manufacturers.

United Kingdom: Fineness marks required by law alongside assay office hallmarks. 375, 585, 750 appear on gold; 925 on silver; 950 on platinum.

Europe (EU): The Vienna Convention standardizes fineness marks across participating countries. 750 is recognized from Portugal to Poland.

Italy: Star mark plus fineness plus provincial code. "750" plus star plus "1 VI" indicates 18K gold assayed in Vicenza province.

France: Fineness may appear alongside (or be implied by) pictorial hallmarks. Eagle head implies 750; no need to stamp "750" separately.

Understanding regional norms helps you assess whether marks are appropriate for where a piece supposedly originated.

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Practical Application

When examining a piece:

1. Find the fineness mark. Use a loupe. Check standard locations.

2. Convert to understand. 750 = 18K = 75% gold. Know what you're looking at.

3. Check for consistency. Does the fineness match what you'd expect for this brand, era, and market?

4. Consider testing. If you're uncertain, XRF testing provides definitive answers.

5. Look for the full picture. Fineness alone isn't authentication—it's one element of the evidence.

Gold fineness marks are among the most standardized and reliable marks on jewelry. Learning to read them fluently gives you a solid foundation for evaluating any piece.

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Tools and Resources

Precious Metals Converter → Convert between karat, fineness, and percentage.

Carat Weight Calculator → Calculate gemstone weights from dimensions.

Gold Hallmarks Guide → Complete guide to gold marking systems.

Platinum Hallmarks → White metal marking systems explained.

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Independent educational resource. Fineness standards reference Vienna Convention documentation and national hallmarking regulations.