Gold Purity Calculator
Convert karats, millesimal fineness, and percentages, then estimate how much pure gold and alloy weight an item contains.
Calculate gold purity, fineness, and pure gold weight.
Enter the purity in the format you know. Add total weight when you want to see how much of the item is fine gold and how much is alloy.
Use a scale if possible. One troy ounce equals 31.1034768 grams; one pennyweight equals about 1.555 grams.
Values are capped at 24K, 1000 fineness, or 100%.
How karat, fineness, and percentage connect.
Karat purity divides a gold alloy into 24 parts. Millesimal fineness expresses the same idea in parts per thousand, which is common for bullion bars and many coin specifications.
Gold purity conversion table.
Use this table to compare common jewelry and bullion markings. Local rules and tolerances can vary, so treat the table as a conversion aid rather than a legal assay result.
| Marking | Fineness | Gold percentage | Common use | Reader check |
|---|---|---|---|---|
| 24K | 999 to 999.9 | 99.9% to 99.99% | Fine bullion, some high-purity jewelry | Soft metal; scratches more easily. |
| 22K | 916 or 916.7 | 91.67% | American Gold Eagle, Krugerrand-style coin alloys, some jewelry | Contains alloy for durability. |
| 18K | 750 | 75.0% | Higher-value jewelry | Richer gold color, less hard than 14K. |
| 14K | 585 | 58.5% | Everyday jewelry in many markets | Durable, but less fine gold by weight. |
| 10K | 417 | 41.7% | Lower-purity jewelry where permitted | More alloy than gold by weight. |
| 9K | 375 | 37.5% | Jewelry in some countries | May be described differently under local rules. |
| 900 | 900 | 90.0% | Historic coin gold | Often coin-specific, not a generic jewelry mark. |
Why higher purity is not always the better choice.
Pure gold has more fine gold by weight, but alloyed gold can be better for durability. The right purity depends on whether the item is worn, collected, stored, or sold for melt value.
| Use case | Typical purity | Why it is used | What to verify |
|---|---|---|---|
| Bullion bars | 995 to 999.9 fine | Market standard favors high purity and clear refiner markings. | Refiner, serial number, fineness, assay documentation. |
| Bullion coins | 22K to 24K | Some coins use alloy for durability while still containing the stated fine gold weight. | Official coin specs, weight, diameter, and dealer documentation. |
| Daily jewelry | 10K to 18K | Alloy improves hardness, wear resistance, and color control. | Hallmark plus testing if value or resale matters. |
| Scrap gold | Varies by item | Broken jewelry and mixed lots are usually valued by fine gold content. | Weight, purity, stones, non-gold parts, and buyer payout rate. |
Useful tools after calculating gold purity.
Use these tools for orientation before comparing buyer offers or deciding whether professional testing is worth it. Home tools reduce uncertainty, but they do not replace assay or XRF verification for high-value items.
Affiliate disclosure: As an Amazon Associate, GoldConsul may earn from qualifying purchases. Prices change and are not shown here.
Best for: basic orientation when checking common jewelry karats.
Caveat: acid testing can mark or damage finishes and should be used conservatively.
Check current price on Amazon
Best for: checking whether weight matches the expected coin, bar, or jewelry description.
Caveat: weight alone cannot prove authenticity or purity.
Check current price on AmazonWhere gold purity estimates can mislead.
The math is simple; the item is often the complicated part. Use the calculator as a starting point, then check the physical details that can change value.
Rose, white, and yellow gold colors come from alloy choices. Color is not a reliable purity test.
A hallmark can be wrong, worn, added later, or applied to only part of a repaired item.
Clasps, stones, enamel, solder, springs, and non-gold parts can distort a simple weight calculation.
FAQ: Gold purity calculator
Short answers to common questions about karats, fineness, hallmarks, and pure gold weight.
How does a gold purity calculator work?
It converts the purity format you enter into the same underlying percentage. It then multiplies that percentage by total item weight to estimate fine gold weight and alloy weight.
What does 14K gold purity mean?
14K gold is roughly 14 parts gold out of 24. In many modern markings it is shown as 585, meaning about 58.5% gold by weight.
Is 999 gold the same as 24K gold?
They are close, but the labels use different systems. 999 means 99.9% gold by weight, while 24K is the traditional highest karat category and is often used for very high-purity gold.
Can a hallmark prove gold purity?
No. A hallmark is useful evidence, but it can be wrong or incomplete. For valuable items, use professional testing, documentation, and buyer terms before making a decision.
Why are some bullion coins 22K instead of 24K?
Some bullion coins use a 22K alloy for durability while still containing a stated amount of fine gold. That means gross weight can be higher than fine gold weight.
Use these tools to check the next number.
Purity is only one part of the value calculation. Weight, live price, and buyer payout determine what the item may be worth.
References for purity standards and markings.
Use stronger references when a claim depends on karat descriptions, fineness markings, bullion specifications, or marketplace standards.
FTC / eCFR Part 23
U.S. guidance on gold content descriptions, karat fineness, and precious-metal marketing claims.
Open source Bullion standardLBMA Good Delivery
Wholesale gold-bar context, including the 995.0 parts-per-thousand minimum fineness standard.
Open source Coin specsU.S. Mint Bullion Programs
Official context for U.S. bullion coin programs and coin specification checks.
Open source