Diamond Size Charts
Carat to Millimeter

Round Brilliant Cut

The most popular diamond shape, maximizing brilliance with 57–58 facets. Measurements given as diameter (mm). Ideal depth ratio: 59–62.5%.

58 Facets Symmetric Best Brilliance Ideal L/W Ratio: 1.0

Round Diamond — Carat to MM

Diameter (mm)	Carat Weight	Approx. Depth	Actual Size	Category

Measurements based on ideal cut proportions. Actual stones may vary ±5%.

How to Measure

Measure the widest diameter across the girdle using calipers. Average two perpendicular readings for irregularly cut stones.

1 Carat Standard

A 1.00 ct round diamond with ideal proportions measures approximately 6.4–6.5 mm in diameter.

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Oval Cut

Elongated shape that makes fingers appear longer. Two measurements: Length × Width. Ideal L/W ratio: 1.30–1.50.

56–58 Facets Elongated Ideal L/W: 1.35–1.45

Oval Diamond — Carat to MM

Length × Width (mm)	Carat Weight	L/W Ratio	Actual Size	Category

Based on 1.35:1 L/W ratio (ideal). Dimensions vary with cutter preference.

Pear Shape (Teardrop)

Combines round and marquise shapes with a pointed tip. Worn with the point toward the fingers for a slimming effect. Ideal L/W: 1.45–1.75.

58 Facets Teardrop Shape Ideal L/W: 1.50–1.70

Pear Diamond — Carat to MM

Length × Width (mm)	Carat Weight	L/W Ratio	Actual Size	Category

Based on 1.60:1 typical L/W ratio. Carat ranges are approximate.

Marquise Cut (Navette)

Boat-shaped with pointed ends, maximising carat weight appearance. Ideal L/W ratio: 1.75–2.25. Recommended with V-prong protection at tips.

55–58 Facets Boat-Shaped Ideal L/W: 1.85–2.10

Marquise Diamond — Carat to MM

Length × Width (mm)	Carat Weight	L/W Ratio	Actual Size	Category

Based on ~2.0:1 L/W ratio. Proportions vary widely for this shape.

Emerald Cut

Step-cut rectangular shape with cut corners. Showcases clarity over brilliance — inclusions are more visible. Ideal L/W ratio: 1.30–1.50.

50–58 Facets Step Cut Ideal L/W: 1.35–1.50

Emerald Diamond — Carat to MM

Length × Width (mm)	Carat Weight	L/W Ratio	Actual Size	Category

Based on 1.40:1 L/W ratio. Step-cut shapes have shallow depth, appearing larger face-up.

Princess Cut

Square shape with pointed corners, the second most popular cut. High brilliance for a square shape. Size given as side length (square).

57–76 Facets Square Ideal L/W: 1.00–1.05

Princess Diamond — Carat to MM

Side Length (mm)	Carat Weight	Approx. Depth	Actual Size	Category

Square measurements. Princess cuts have deeper pavilions than round diamonds.

Cushion Cut

Square or rectangular with rounded corners and large facets that enhance clarity. Available in “classic” and “modified” variants. Ideal L/W: 1.00–1.09.

58–64 Facets Soft Corners Ideal L/W: 1.00–1.05

Cushion Diamond — Carat to MM

Length × Width (mm)	Carat Weight	Approx. Depth	Actual Size	Category

Square cushion (1.00 L/W) measurements shown. Elongated cushions are 1.15–1.30.

Heart Shape

The most romantic diamond shape. Requires skilled cutting for symmetry. Size given as width. Ideal L/W ratio: 0.90–1.10 (near 1:1).

56–58 Facets Romantic Ideal L/W: 0.95–1.05

Heart Diamond — Carat to MM

Width (mm)	Carat Weight	Approx. Height	Actual Size	Category

Based on 1:1 L/W ratio. Heart shape benefits from larger sizes (0.50 ct+) for cleft visibility.

Elongated Radiant Cut

A rectangular brilliant-cut with cropped corners — combines the fire of a round with the elegance of an emerald outline. More popular than the square version. Ideal L/W: 1.25–1.50.

62–70 Facets Brilliant Facets Ideal L/W: 1.25–1.50

Elongated Radiant Diamond — Carat to MM

Length × Width (mm)	Carat Weight	L/W Ratio	Actual Size	Category

Based on 1.35:1 L/W ratio (ideal elongated). Radiant cuts appear larger face-up than rounds of the same carat.

Asscher Cut

A square step-cut with deeply cropped corners resembling an octagon. Created in 1902. Distinctive “hall of mirrors” effect. Nearly square L/W: 1.00–1.05.

58 Facets Step Cut Vintage Style Ideal L/W: 1.00–1.05

Asscher Diamond — Carat to MM

Side Length (mm)	Carat Weight	Approx. Depth	Actual Size	Category

Square measurements. Asscher cuts appear smaller face-up than rounds of the same carat due to deep pavilion.

Trillion Cut (Trilliant)

Triangular shape with three equal sides. Used as solitaire or flanking side stones. Measurement is the width across the widest point (side length).

31–50 Facets Triangular Equilateral

Trillion Diamond — Carat to MM

Side Length (mm)	Carat Weight	Approx. Depth	Actual Size	Category

Equilateral triangle measurements. Curved vs. straight-sided variants may differ by ±3%.