Gold Purity Calculator
Calculate gold purity percentage, understand karats, and verify hallmarks. Select your gold karat below to see purity and value.
Understanding Gold Purity
Gold purity refers to the proportion of pure gold in an alloy. Pure gold (24 karat) is too soft for jewelry, so it's mixed with other metals like copper, silver, or zinc to increase durability. The purity is measured in karats (K) or expressed as fineness (parts per thousand).
Gold Purity Chart - Karat to Percentage
| Karat | Purity % | Fineness | Hallmark | Common Use |
|---|---|---|---|---|
| 24K | 99.9% | 999 | 999 | Coins, bars, investment |
| 23K | 95.83% | 958 | 958 | High-purity jewelry |
| 22K | 91.67% | 916 | 916 | Indian/Middle East jewelry |
| 21K | 87.5% | 875 | 875 | Middle East jewelry |
| 18K | 75% | 750 | 750 | Western fine jewelry |
| 14K | 58.33% | 585 | 585 | US/Europe everyday jewelry |
| 12K | 50% | 500 | 500 | Budget jewelry |
| 10K | 41.67% | 417 | 417 | Minimum legal gold (US) |
How to Check Gold Purity
1. Check the Hallmark
Look for stamped marks like "916" (22K), "750" (18K), or "585" (14K). In India, look for the BIS hallmark with HUID (6-digit alphanumeric code).
2. Acid Test
Professional jewelers use nitric acid on a small scratch. Pure gold doesn't react, while lower karats change color based on alloy content.
3. Electronic Tester
Karat meters use electrical conductivity to measure purity. Non-destructive and accurate to within 0.5 karat. Available at jewelry stores.
4. XRF Analysis
X-ray fluorescence provides the most accurate reading. Used by refiners and assay offices. Shows exact composition of all metals.
BIS Hallmark in India
Since June 2021, hallmarking is mandatory for gold jewelry in India. A valid BIS hallmark contains:
- BIS Logo: Triangle with BIS mark
- Purity Grade: 999, 916, 750, or 585
- HUID: 6-character Hallmark Unique Identification number
Verify HUID: Visit the BIS Care app or website to verify any HUID code and check the jeweler's authenticity before purchase.
Gold Purity Formula
Purity Percentage = (Karat / 24) × 100
Example: 22K purity = (22 / 24) × 100 = 91.67%
Home Tests (Less Accurate)
Magnet Test
Pure gold is non-magnetic. If attracted to magnet, contains iron/nickel alloys.
Float Test
Pure gold sinks quickly in water due to high density (19.3 g/cm³).
Skin Test
Lower karat gold may leave green/black marks on skin due to copper content.
Warning: Home tests are not reliable for determining exact karat. Always get professional verification for valuable pieces or before selling gold.
Calculate Gold Value by Purity
Select your gold karat in our calculator to see the exact value based on purity.
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