1. Karat Math & Metallurgical Composition
The word "Karat" (abbreviated K) measures the purity of gold expressed in parts out of 24. Pure elemental gold is rated as 24 Karat (24/24 parts gold). When crafting wearable jewellery, pure gold is too soft and malleable: it easily bends, scratches, and loses stone settings.
To solve this, jewellers blend pure gold with strengthening alloy metals such as copper, silver, zinc, or nickel. The exact purity fraction determines the official Bureau of Indian Standards (BIS) fineness rating:
24K Gold (999 Fineness)
Formula: (24 / 24) × 100 = 99.9% pure gold.
Contains zero alloy metals. Has a deep yellow luster. Used exclusively for bullion bars, sovereign minted coins, and digital gold.
22K Gold (916 Fineness)
Formula: (22 / 24) × 100 = 91.67% pure gold.
Blended with 8.33% copper and silver for structural strength. Traditional benchmark for Indian bridal necklaces, bangles, and temple jewellery.
18K Gold (750 Fineness)
Formula: (18 / 24) × 100 = 75.00% pure gold.
Blended with 25.0% alloy metals. Significantly harder alloy required for diamond prongs, solitaire rings, and daily wear luxury items.
2. BIS HUID Verification: 6-Digit Code Authentication
Under Ministry of Consumer Affairs rules, all hallmarked gold jewellery sold in India must bear the mandatory 6-digit alphanumeric HUID (Hallmark Unique Identification) code. This laser-engraved code links every individual article to the BIS central registry.
How to Verify HUID in 3 Steps using the BIS Care App:
3. Price-per-Gram Formula Across Karats
The daily baseline rate for 22K and 18K gold is calculated directly from the live 24K spot rate (as detailed in our Gold Price Calculation Guide):
| Karat Grade | Fineness Stamp | Purity % | Per Gram Pricing Formula | Primary Use Case |
|---|---|---|---|---|
| 24 Karat | 24K999 | 99.9% | 24K Base Rate | Investment Bars, Minted Coins |
| 22 Karat | 22K916 | 91.6% | 24K Rate × 0.916 | Bridal Chains, Bangles, Necklaces |
| 18 Karat | 18K750 | 75.0% | 24K Rate × 0.750 | Diamond Solitaires, Daily Rings |
| 14 Karat | 14K585 | 58.5% | 24K Rate × 0.585 | Lightweight Western Fashion Wear |
4. Buyer Decision Framework: Investment vs Bridal vs Daily Wear
Choose your purity karat grade based on your specific objective:
For Pure Capital Investment
Buy 24K Gold Coins/Bars or tax-free Sovereign Gold Bonds (SGB). You pay minimal making charges (1-3%) and avoid losing 8-25% to jeweller manufacturing markups.
For Traditional Bridal Jewellery
Choose 22K (916 Gold). It provides maximum golden color intensity while maintaining adequate copper/silver strength for heavy necklaces and bangles.