Gold Purity Calculator - Fineness to Karat | 1Dollars

Free Gold Purity Calculator

Convert a gold fineness mark such as 999, 916, 750 or 585 into purity percentage, decimal fineness and mathematical karat. Add the item's weight to estimate its fine-gold and other alloy-metal content.

Gold Fineness to Karat Calculator

Enter purity as parts per thousand, percentage or decimal fineness. The tool converts all three formats and identifies the nearest common gold-grade reference.

Common gold fineness marks

Enter parts per thousand from above 0 to 1000.

Mathematical Karat Equivalent21.984K
Millesimal fineness916
Gold purity percentage91.6%
Decimal fineness0.916
Nearest common grade22K / 916
Difference from reference0 fineness points
Total alloy weight10 g
Fine-gold content9.16 g
Other alloy-metal content0.84 g
Fine gold in troy ounces0.294501 ozt

916 fineness is a common 22K reference grade. Mathematical conversion gives 21.984K because 916 means exactly 91.6% in this calculation.

This calculator interprets the entered number mathematically. It does not test the item, authenticate a hallmark or determine whether a mark complies with local law.

Reviewed on 15 July 2026 using BIS gold-fineness grades, World Gold Council purity information, NIST troy-weight conversions and current U.S. FTC jewelry guidance.

Gold purity may appear as a three-digit fineness mark, a percentage or a decimal. This calculator normalizes any of those formats, converts purity to mathematical karat and compares the result with common reference grades without claiming that the item has been assayed or hallmarked.

Quick answer: Enter 916, 91.6 or 0.916 and select the matching format. Each represents 91.6% gold and converts mathematically to 21.984K, commonly referenced as 22K / 916.

How the Gold Purity Calculator Works

Fineness states the proportion of gold in an alloy. Millesimal fineness uses parts per thousand, percentage uses parts per hundred, and decimal fineness uses a value from above zero to one. Once normalized, the conversion to karat is direct.

Purity percentage = millesimal fineness ÷ 10
Decimal fineness = millesimal fineness ÷ 1,000
Mathematical karat = decimal fineness × 24
Fine-gold weight = total alloy weight × decimal fineness

Gold Purity Input Formats

Parts per thousandEnter the hallmark-style number directly, such as 999, 916, 750 or 585.
PercentageEnter the gold share out of 100, such as 99.9%, 91.6%, 75% or 58.5%.
Decimal finenessEnter the gold share as a decimal, such as 0.999, 0.916, 0.750 or 0.585.
Karat outputThe result is a mathematical equivalent. A trade label may round to a familiar karat grade.

Gold Fineness to Karat Conversion Chart

Fineness markPurityMathematical karatCommon reference
99999.9%23.976K24K / 999
99599.5%23.880K24K / 995
95895.8%22.992K23K / 958
91691.6%21.984K22K / 916
87587.5%21.000K21K / 875
83383.3%19.992K20K / 833
75075.0%18.000K18K / 750
58558.5%14.040K14K / 585
41741.7%10.008K10K / 417
37537.5%9.000K9K / 375

BIS laboratory scope information for IS 1417 lists yellow-gold jewelry grades 9K375, 14K585, 18K750, 20K833, 22K916 and 23K958, plus 24KS995 and 24KF999 for gold alloy or bullion. Availability, marking rules and permitted tolerances can vary by product and jurisdiction.

Worked 916 Gold Purity Example

For a 10-gram item marked 916:

  • Purity percentage = 916 ÷ 10 = 91.6%
  • Decimal fineness = 916 ÷ 1,000 = 0.916
  • Mathematical karat = 0.916 × 24 = 21.984K
  • Fine-gold content = 10 g × 0.916 = 9.16 g
  • Other alloy-metal content = 10 g − 9.16 g = 0.84 g

The common reference is 22K / 916. The mathematical output is not rounded before calculating fine-gold weight.

Why Mathematical Karat May Not Be a Whole Number

A fineness specification and an exact karat fraction can differ slightly. For example, 585 × 24 ÷ 1,000 equals 14.04K, while exact 14 ÷ 24 equals 58.3333% or 583.333 fineness. The World Gold Council notes that many manufacturers use 585 for 14-carat jewelry.

Similarly, 999 fineness converts to 23.976K rather than a mathematical 24.000K. It is nevertheless commonly described as a 24K / 999 reference grade. The calculator shows both the unrounded arithmetic and nearest familiar grade.

Hallmark Fineness Is Not an Assay Result

A number stamped on jewelry is an input to this calculator, not proof of composition. A qualified hallmark verification or assay is needed to establish actual gold content. Repairs, solder, wear, mixed components, plating, counterfeit marks and non-gold parts can affect the relationship between the stamp and the item's true content.

Use the correct weight: remove or separately account for gemstones, enamel, watch movements, steel parts and other non-gold material when estimating fine-gold weight.

Purity Does Not Equal Gold Value

Purity determines the proportion of gold, but monetary value also requires a current gold price, eligible net weight, price unit, recovery assumption, buyer payout, fees and possible collectible value. This page intentionally performs no live-price lookup.

Supported Weight Units

The optional weight calculation accepts grams, kilograms, troy ounces, tola, pennyweight and grains. It converts the entered amount to grams before calculating fine-gold and alloy-metal content. One troy ounce equals 31.1034768 grams.

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Frequently Asked Questions

What does 916 mean on gold?
916 means 916 parts gold per thousand, equal to 91.6% purity. Its mathematical equivalent is 21.984K and its common reference is 22K / 916.
What does 750 mean on gold?
750 fineness means 75% gold. Multiplying 0.750 by 24 gives exactly 18K.
What does 585 mean on gold?
585 means 58.5% gold and converts mathematically to 14.04K. It is commonly used as a 14K / 585 reference.
What does 999 gold purity mean?
999 means 999 parts gold per thousand, or 99.9%. It converts mathematically to 23.976K and is commonly referenced as 24K / 999.
How do I convert gold fineness to karat?
Divide fineness by 1,000 and multiply by 24. For example, 916 ÷ 1,000 × 24 = 21.984K.
How do I convert gold percentage to karat?
Divide the percentage by 100 and multiply by 24. For example, 75 ÷ 100 × 24 = 18K.
Why does 916 convert to 21.984K instead of exactly 22K?
The calculator uses 91.6% exactly. Exact 22 ÷ 24 equals 91.6667%, while the common 916 mark represents 91.6%.
Can I enter a custom assay fineness?
Yes. Enter any valid fineness above zero and no more than 1,000, or use its percentage or decimal equivalent. The calculator will show the nearest common reference separately.
Does the nearest grade verify my gold hallmark?
No. It is only the closest reference in the calculator's comparison list. Testing or official hallmark verification is needed to confirm an item's actual fineness.
Does gold color determine purity?
No. Yellow, white and rose gold can be produced at several purity levels using different alloy metals. Use a verified fineness or assay rather than color alone.

Reference Sources

Disclaimer: This calculator and guide provide general mathematical estimates, not a hallmark verification, assay, appraisal, live gold price, buyer quote, legal determination or investment advice. Verify actual weight, fineness and applicable local requirements independently.