Round Diamond Size Chart (Carat to MM)

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
Round diamond carat weight to diameter in millimeters.
Carat WeightDiameter (mm)Height (mm)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.

Our diamonds

Oval Diamond Size Chart (Carat to MM)

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
Oval diamond carat weight to length and width in millimeters.
Carat WeightLength (mm)Width (mm)Height (mm)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
Pear-shaped diamond carat weight to length and width in millimeters.
Carat WeightLength (mm)Width (mm)Height (mm)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
Marquise diamond carat weight to length and width in millimeters.
Carat WeightLength (mm)Width (mm)Height (mm)Category
Based on ~2.0:1 L/W ratio. Proportions vary widely for this shape.

Emerald Diamond Size Chart (Carat to MM)

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
Emerald-cut diamond carat weight to length and width in millimeters.
Carat WeightLength (mm)Width (mm)Height (mm)Category
Based on 1.40:1 L/W ratio. Step-cut shapes have shallow depth, appearing larger face-up.

Princess Diamond Size Chart (Carat to MM)

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
Princess-cut diamond carat weight to side length in millimeters.
Carat WeightSide (mm)Height (mm)Category
Square measurements. Princess cuts have deeper pavilions than round diamonds.

Cushion Diamond Size Chart (Carat to MM)

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
Cushion-cut diamond carat weight to length and width in millimeters.
Carat WeightSize (mm)Height (mm)Category
Square cushion (1.00 L/W) measurements shown. Elongated cushions are 1.15–1.30.

Heart Diamond Size Chart (Carat to MM)

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
Heart-shaped diamond carat weight to width in millimeters.
Carat WeightWidth (mm)Height (mm)Category
Based on 1:1 L/W ratio. Heart shape benefits from larger sizes (0.50 ct+) for cleft visibility.

Radiant Diamond Size Chart (Carat to MM)

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
Radiant-cut diamond carat weight to length and width in millimeters.
Carat WeightLength (mm)Width (mm)Height (mm)Category
Based on 1.35:1 L/W ratio (ideal elongated). Radiant cuts appear larger face-up than rounds of the same carat.

Asscher Diamond Size Chart (Carat to MM)

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
Asscher-cut diamond carat weight to side length in millimeters.
Carat WeightSide (mm)Height (mm)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
Trillion-cut diamond carat weight to side length in millimeters.
Carat WeightSide (mm)Height (mm)Category
Equilateral triangle measurements. Curved vs. straight-sided variants may differ by ±3%.