Carats vs Karats: Understanding Jewelry Measurements (Millimeters, Carats & Karats Explained)

Carats, karats, and millimeters—three different measurements that confuse everyone. One measures stone weight, one measures gold purity, and one measures actual size. Here's the complete guide to understanding all three and why they matter when shopping at Bling Authority.

The Big Confusion: Carats vs Karats

These two words sound identical but measure completely different things:

• Carat (with a C): Measures the weight of gemstones and diamonds
• Karat (with a K): Measures the purity of gold

Let's break down each one.

What Is a Carat? (Stone Weight)

The Basics

• 1 carat = 200 milligrams (0.2 grams)
• Measures how much a gemstone or diamond weighs
• Abbreviated as "ct" or "carat"
• Used for diamonds, CZ, moissanite, and all gemstones

Important: Weight ≠ Size

Two stones can have the same carat weight but different sizes depending on:

• Cut: A shallow cut looks bigger than a deep cut at the same weight
• Density: CZ is denser than diamond, so a 1-carat CZ is slightly smaller than a 1-carat diamond
• Shape: Round, oval, emerald cuts all look different at the same carat weight

Carat Weight Examples

• 0.25 carats: Small accent stone
• 0.50 carats: Modest solitaire
• 1.00 carat: Classic engagement ring size
• 2.00+ carats: Statement stone

What Is a Karat? (Gold Purity)

The Basics

• Measures the purity of gold in jewelry
• Scale goes from 1K to 24K (24K = pure gold)
• Abbreviated as "K" or "kt"
• Only applies to gold—not stones

Common Karat Levels

• 24K: 99.9% pure gold (too soft for jewelry)
• 18K: 75% gold, 25% alloy metals (the sweet spot)
• 14K: 58.5% gold, 41.5% alloy metals
• 10K: 41.7% gold, 58.3% alloy metals (barely "gold")

Why 18K Is Best

At Bling Authority, we use heavy 18K plating because:

• Rich color: Deep, warm gold tone that photographs beautifully
• High gold content: 75% pure gold for luxe appearance
• Perfect balance: Durable enough for daily wear, soft enough for intricate work
• Professional standard: What high-end jewelers use worldwide

Carats vs Karats: Side-by-Side

What Are Millimeters? (Actual Size)

The Most Practical Measurement

Millimeters measure actual physical size—what you see and what matters for jewelry:

• Chain widths: 3mm, 4mm, 12mm tell you exactly how wide the chain is
• Stone diameters: A 6.5mm round stone looks like a 1-carat diamond
• Bracelet sizing: Wrist measurement in centimeters
• Necklace lengths: 50 cm (20"), 55 cm (22"), 60 cm (24")

Why Bling Authority Uses Millimeters

Millimeters are more accurate and practical than carats for chains and jewelry:

• No guessing: 3mm means exactly 3mm wide
• Easy comparison: Compare 3mm tennis vs 12mm Cuban instantly
• Professional standard: How high-end jewelers measure
• Consistent quality: Every stone cut to exact millimeter specs

Millimeters to Carats Conversion (For Stones)

If you're comparing stone sizes, here's how millimeters relate to approximate carat weight for round stones:

Small Stones (Tennis Chain Size)

• 2mm round: ≈ 0.03 carats
• 2.5mm round: ≈ 0.06 carats
• 3mm round: ≈ 0.10 carats
• 3.5mm round: ≈ 0.15 carats
• 4mm round: ≈ 0.25 carats

Medium Stones

• 5mm round: ≈ 0.50 carats
• 6mm round: ≈ 0.75 carats
• 6.5mm round: ≈ 1.00 carat
• 7mm round: ≈ 1.25 carats

Larger Stones (Pendant Size)

• 8mm round: ≈ 2.00 carats
• 9mm round: ≈ 2.75 carats
• 10mm round: ≈ 3.50 carats

Note: CZ and diamonds have different densities, so these are approximations. Millimeters are more reliable for sizing.

How Bling Authority Uses All Three Measurements

Karats (Gold Purity)

We use heavy 18K plating on all our pieces:

• 75% pure gold for rich, luxurious color
• Up to 10x thicker than typical boutique plating
• Long-lasting shine that resists daily wear
• Available in white, yellow, and rose gold finishes

Millimeters (Chain & Stone Size)

We measure everything in millimeters for accuracy:

• 3mm Tennis Chain: Minimalist daily shine
• 4mm Tennis Chain: Everyday standout
• 12mm Cuban Link: Bold statement
• Premium CZ stones: Cut to exact millimeter specs

Carats (Total Stone Weight)

While we don't advertise carat weight, our tennis chains pack serious sparkle:

• 3mm Tennis (50 cm/20"): ≈ 8–10 carats total CZ
• 4mm Tennis (50 cm/20"): ≈ 17.5–22.5 carats total CZ

Real-World Examples

Example 1: Tennis Chain

• Karat: Heavy 18K plating (gold purity)
• Millimeters: 4mm wide chain (actual width)
• Carats: Each stone ≈ 0.25 carats (stone weight)
• Result: 18K-plated 4mm tennis chain with premium CZ stones

Shop 4mm Tennis Chain

Example 2: Cuban Link Chain

• Karat: Heavy 18K plating (gold purity)
• Millimeters: 12mm wide chain (actual width)
• Carats: Premium CZ stones in iced version (stone weight)
• Result: 18K-plated 12mm iced Cuban with bold presence

Shop 12mm Iced Cuban

Why Premium CZ Beats Carat Obsession

At Bling Authority, we focus on quality over carat weight:

What Makes Our CZ Superior

• Crisp faceting: Precise cuts that maximize light reflection
• Consistent color: Near-colorless stones that match perfectly
• Clean clarity: No cloudiness—just sparkle
• Exact sizing: Every stone cut to millimeter specs
• Secure settings: Smooth prongs that hold tight

Why This Matters More

A poorly cut 1-carat stone looks worse than a well-cut 0.75-carat stone. We prioritize:

• Cut quality over carat weight
• Consistent sizing over maximum size
• Even sparkle over stone count
• Professional setting over carat claims

Shopping Guide: Choose by Millimeters

Tennis Chains (Width)

• 3mm: Clean, minimalist—Shop 3mm
• 4mm: More presence—Shop 4mm
• 5–6mm: Statement sparkle

Cuban Link Chains (Width)

• 5–8mm: Bold daily look
• 12mm: Heavy statement—Shop 12mm

Necklace Lengths

• 45 cm (18"): Sits high; choker vibe
• 50 cm (20"): Universal sweet spot
• 55 cm (22"): Adds drop; layers well
• 60 cm (24"): Relaxed over hoodies

Quick Reference Chart

When to Use Each Measurement

• Karats (K): Checking gold purity—look for 18K
• Carats (ct): Comparing loose stones or engagement rings
• Millimeters (mm): Choosing chain width, stone size, bracelet fit

Bling Authority Standards

• Gold purity: Heavy 18K plating (up to 10x thicker)
• Chain widths: 3mm, 4mm, 12mm (exact measurements)
• Stone quality: Premium CZ cut to precise millimeter specs
• Lengths: 50 cm (20"), 55 cm (22"), 60 cm (24")

Shop Bling Authority Collections

• Tennis Chains — 18K-plated sparkle
• Cuban Link Chains — 18K-plated texture
• Cuban Link Bracelets — Wrist symmetry
• Pendants — Meaningful symbols

The Bottom Line

Karats (K) measure gold purity—18K is the sweet spot for rich color and durability.

Carats (ct) measure stone weight—useful for loose stones, but millimeters are more practical for jewelry.

Millimeters (mm) measure actual size—the most accurate way to choose chains, stones, and bracelets.

At Bling Authority, we combine all three: heavy 18K plating for luxe gold color, premium CZ stones cut to exact millimeter specs, and clear sizing so you know exactly what you're getting. No inflated claims, no guessing—just quality jewelry that looks and feels premium.