Karat and Purity
The term karat (abbreviated K or kt) refers to the proportion of pure gold present in an alloy, on a scale of 24 parts.
Although the karat system formally applies to gold, analogous purity conventions exist for other precious metals such as silver,
platinum, and palladium. This page standardizes the mathematical purity factors (φ) used in our calculators and
price displays. All figures are derived from publicly available, verifiable standards published by government
bodies and recognized industry organizations.
For authoritative background, see:
U.S. Federal Trade Commission (FTC) – Jewelry Guides, Subpart C,
London Bullion Market Association – Good Delivery Rules,
and
Encyclopædia Britannica – Karat.
1. Gold and the Karat System
In scientific notation, the purity fraction of gold in karat form is expressed as:
φK = K / 24.
Thus, 24 karat (24K) gold is considered pure (φ = 1.0000), while 18K gold contains 18 parts of gold and 6 parts of
other metals such as copper, silver, nickel, or zinc (φ = 0.7500).
The modern 24-karat scale was formalized under international trade standards and is widely recognized in ISO 8654 (“Designation and composition of gold alloys for jewellery”).
ISO 8654 is managed by the International Organization for Standardization and sets the nominal gold content for alloys
used in jewelry manufacture, ensuring compliance with hallmarking standards across different jurisdictions.
See:
ISO 8654:2019 – Jewellery alloys of gold, palladium, silver, and platinum.
| Karat (K) | Purity fraction (φ = K / 24) | Fine gold (%) |
|---|---|---|
| 24 K | 1.0000 | 99.9 – 99.99% |
| 23 K | 0.9583 | 95.83% |
| 22 K | 0.9167 | 91.67% |
| 21 K | 0.8750 | 87.50% |
| 20 K | 0.8333 | 83.33% |
| 18 K | 0.7500 | 75.00% |
| 14 K | 0.5833 | 58.33% |
| 12 K | 0.5000 | 50.00% |
| 10 K | 0.4167 | 41.67% |
| 9 K | 0.3750 | 37.50% |
| 8 K | 0.3333 | 33.33% |
Scientific basis and examples
Pure gold (atomic symbol Au, atomic weight = 196.97 u) has a density of approximately 19.32 g/cm³ at 20 °C.
Because of its softness, it is alloyed with metals such as Cu (copper, Z = 29), Ag (silver, Z = 47), Ni (nickel, Z = 28), or Zn (zinc, Z = 30)
to improve hardness and color. For example, the 22K alloy used in South Asian and Middle Eastern jewelry typically contains
~91.67% Au and ~8.33% Cu/Ag blend; 18K white gold might contain ~75% Au, ~10% Ni, and ~15% Pd.
International hallmarking standards require the fineness (parts per thousand of gold) to be stamped on jewelry:
e.g., “750” for 18K, “916” for 22K, “999” for 24K. This is codified under the U.S. Public Law 109-58 (Jewelry Labeling) and
national hallmarking conventions such as the UK Assay Offices and the Bureau of Indian Standards.
2. Silver Purity Standards
Although “karat” is not used for silver, similar purity classifications exist. The fineness system denotes parts of pure silver per 1 000 parts alloy. The primary global standards are published by ISO 9202 (“Jewellery – Fineness of precious metal alloys”) and the London Bullion Market Association (LBMA) Good Delivery Rules. See: ISO 9202:2019, LBMA Good Delivery Rules.
| Designation | Purity (‰) | Equivalent % Ag |
|---|---|---|
| Fine silver | 999 – 999.9 | 99.9 – 99.99% |
| Sterling silver | 925 | 92.5% |
| Coin silver | 900 | 90.0% |
| Britannia silver | 958 | 95.8% |
| Argentium silver | 960 | 96.0% |
The atomic symbol of silver is Ag (Latin argentum), atomic number 47. Pure silver has density 10.49 g/cm³, melting point 961.8 °C, and a distinct reflectivity used in electronics, coins, and jewelry. Alloying with copper (Cu) increases hardness and tarnish resistance. The 92.5% standard of sterling silver is recognized under ISO 9202 and the United Kingdom Hallmarking Act 1973.
3. Platinum Purity Standards
Platinum (Pt, Z = 78) belongs to the platinum-group metals (PGMs). Its trade and hallmark standards are likewise governed by ISO 9202 and ISO 11210. Common platinum finenesses are 999 (99.9%), 950 (95%), and 900 (90%). These values correspond to jewelry hallmark stamps such as “Pt950”. See: ISO 9202:2019 – Fineness of precious metal alloys and LBMA Good Delivery Rules (Platinum & Palladium).
| Mark | Purity (‰) | Common use |
|---|---|---|
| Pt999 | 999 | Investment bars |
| Pt950 | 950 | High-end jewelry |
| Pt900 | 900 | Durable jewelry and coins |
| Pt850 | 850 | Older Asian jewelry |
Platinum’s density (21.45 g/cm³) exceeds that of gold, and it resists corrosion even at temperatures exceeding 1 700 °C. Because of its rarity, platinum is traded primarily through LBMA-certified refiners. Hallmarking is legally required in the UK, EU, Japan, and other markets under respective assay laws.
4. Palladium Purity Standards
Palladium (Pd, Z = 46) is another PGM and shares chemical similarities with platinum. Jewelry and bullion standards are defined by ISO 9202 and LBMA Good Delivery Rules. Common purities include Pd999, Pd950, and Pd500 (depending on alloy and application). See: LBMA Good Delivery Rules (Palladium) and ISO 9202:2019.
| Mark | Purity (‰) | Notes |
|---|---|---|
| Pd999 | 999 | Investment-grade bullion |
| Pd950 | 950 | Jewelry alloy standard |
| Pd500 | 500 | Industrial alloys |
Palladium’s density (12.02 g/cm³) and melting point (1 555 °C) make it ideal for catalyst converters and fine jewelry. ISO standards require clear fineness stamping (e.g., “Pd950”) when used in hallmarked pieces.
5. Conversion Formula (applied in calculators)
The purity-based conversion used for pricing and calculators across all metals follows:
Punit,metal,CCY = Punit,CCY × φmetal
where Punit,metal,CCY is the price of the metal unit at a given purity in currency (CCY), and φmetal is the decimal purity factor (karat/24 for gold or fineness ÷ 1000 for others).
6. Legal and Liability Disclaimer
All material on this page is provided for general informational and educational purposes only. It does not constitute financial, investment, or hallmarking advice, and may not reflect the latest legal or regulatory changes in every jurisdiction. We rely on official sources such as ISO, LBMA, FTC Jewelry Guides, and national metrology institutions for data, but users should confirm specifications with their local assay office, refiner, or bullion authority before conducting any transaction or hallmarking process. The operators of this website disclaim all liability for errors, omissions, or actions taken in reliance upon the information herein, to the fullest extent permitted by applicable law. Use of this information is subject to our website disclaimer and applicable policies.
Related: Methodology Hub.
Last Updated: 15 November 2025
Silver Purity/types:
Unlike gold, silver is typically not classified by karats. Instead, silver purity is usually expressed as a percentage or parts per thousand. The most common purities are:
- Fine Silver (99.9%): Used in investment-grade bullion, coins, and bars.
- Sterling Silver (92.5%): Common in jewelry, silverware, and decorative items.
- Coin Silver (90%): Previously used in coins, now less common.
- Other Alloys: Lower purity silver used in budget or industrial applications.
Silver purity is often marked with stamps like "999," "925," or "900" to indicate the purity level.
- About Silver Types (in Detail),- Methodologies, and References
Description of Weight Units:
| Weight Unit | Equivalent in Grams |
|---|---|
| Troy Ounce | 31.1035 |
| Kilogram | 1000 |
| Baht | 15.244 |
| Tola | 11.664 |
| Vori (Bori) | 11.664 |
| Pennyweight | 1.555 |
| Pound | 453.592 |
| Grain | 0.065 |
| Ratti | 0.121 |
| Carat | 0.2 |
| Masha | 3.885 |
| Tael (Hong Kong) | 37.429 |
Description for currency:
Select your preferred currency to view silver prices. Prices are available in major global currencies like USD, EUR, GBP, and more. Choosing the correct currency ensures you see accurate and up-to-date pricing based on the exchange rate for your location or preference.
Live Silver Price Chart:
Use the duration options to view silver price trends over different time periods. 'Today' shows the current day's price movements, while '7 Days,' 'Month,' and '30 Days' provide recent trends. 'YTD' (Year-to-Date) and '1 Year' offer a longer-term view. Select 'More' for additional timeframes and detailed analysis.
This performance section provides an overview of silver price trends. The Summary tab offers an at-a-glance view with color-coded trend indicators showing percentage changes across key time horizons.
The Amount tab displays absolute value changes in both USD (global benchmark) and local currency, along with exchange rate movements, enabling precise profit/loss calculations.
The Percent tab reveals relative growth rates, essential for comparing silver's performance against other assets and inflation.
The History tab provides anchor price points on specific dates, supporting technical analysis and investment strategy backtesting.
Together, these tabs offer investors, jewelers, and economists multidimensional insights into silver's behavior across timeframes and currency perspectives.
Live Silver Price Calculator:
This tool estimates silver values using live market rates. Enter your silver weight, select a measurement unit (grams, tolas, ounces, etc.), and choose any currency. Click "Calculate" for instant valuation based on current prices. You can also switch tabs to value gold or convert currencies. All calculations reflect real-time market data for accurate precious metal valuation.
About this timestamp
The time shown here indicates when the price data was last fetched from our server. It is not the exact moment of a retail sale or trade, and may differ slightly from jewellery shops or live trading platforms because of data provider timing and currency conversion.
For transparency, full details of how prices are calculated and updated are available in the Reference section. There you can see the data sources, update frequency, and notes on what is included or excluded.
Silver Price Comparison by Purity:
This tool compares live silver prices across different purity levels and weight units. Switch between tabs to see values per ounce, gram, tola, or select "More" for units like baht, tael, etc. Each table shows today's current, lowest, and highest prices for every purity type in your chosen currency. Use the dropdown filters to focus on specific purities, switch weight measurements, or convert values to any global currency.
Silver Market Price Tool
This section shows live silver pricing with bid/ask spreads and customization options. View real-time market rates for different purity levels using the top tabs. The table displays three key prices per gram:
1. Current Price: Latest market rate
2. Bid Price: What buyers offer
3. Ask Price: What sellers request
Adjust the spread percentage to see how dealer margins affect prices, or add labor costs for jewelry valuation. Use the dropdowns to switch between purity levels, weight units, or currencies for international comparisons.
Silver Quantity Calculator Guide
This tool calculates silver prices for specific quantities in Pakistani Rupees. Select a weight unit (grams, tolas, ounces) using the tabs, or choose other units like "baht", "tael", etc. from the "More" dropdown. The table instantly shows spot, buy, and sell prices for common quantities (1, 5, 10 units) and allows custom quantity entry.
Key features:
1. Custom Quantity: Enter any amount for instant valuation
2. Spread Adjustment: Modify dealer margin spreads
3. Labor Costs: Add manufacturing fees for jewelry valuation
4. Live Rates: All prices update in real-time based on market data
Use the dropdowns to change silver purity, weight units, or convert prices to other currencies.
Silver Price History
This section tracks silver's value over time. The table shows daily prices with percentage changes, highlighting market activity and closures.
Reference Information
The following information is about the primary data used in the above sections for transparency and trustworthiness. This section details the weight unit, purity, and currency. It also provides update times and data sources to ensure all information is fresh and accurate for decision-making.