Lab Grown Diamond Ideal Cut Proportions: The Definitive Reference Chart

Diamond proportions determine everything about how your lab grown diamond handles light. This comprehensive reference brings together ideal ranges for every major proportion across all popular diamond shapes — your one-stop guide for evaluating any diamond's cut quality.

Round Brilliant — Ideal Proportions

Parameter	Ideal	Excellent	Very Good
Table %	54-57%	52-58%	50-62%
Depth %	59.5-62%	59-62.5%	57.5-63.5%
Crown Angle	34-35°	33.5-35.5°	32-36.5°
Pavilion Angle	40.6-41°	40.4-41.2°	40-41.6°
Crown Height %	14.5-16%	13.5-16.5%	12-17.5%
Pavilion Depth %	42.5-43.5%	42-44%	41-45%
Girdle	Thin-Medium	Thin-Sl. Thick	V.Thin-Thick
Culet	None	None-V.Small	None-Small
Star Length %	50-55%	45-65%	40-70%
Lower Half %	75-80%	70-85%	65-90%
Symmetry	Excellent	Excellent	Very Good
Polish	Excellent	Excellent	Very Good

For Hearts & Arrows: Table 54-56%, Depth 60.5-61.5%, Crown 34.3-34.8°, Pavilion 40.6-40.9°.

Princess Cut

Parameter	Ideal	Good
Table %	67-72%	62-77%
Depth %	64-75%	58-78%
L/W Ratio (square)	1.00-1.05	1.00-1.10
Girdle	Thin-Sl. Thick	V.Thin-Thick
Culet	None-V.Small	None-Small

Oval Cut

Parameter	Ideal	Good
Table %	53-63%	50-66%
Depth %	58-62%	56-65%
L/W Ratio	1.35-1.50	1.25-1.60
Girdle	Thin-Sl. Thick	V.Thin-Thick
Bow-Tie	Minimal	Moderate

Emerald Cut

Parameter	Ideal	Good
Table %	61-69%	57-72%
Depth %	61-67%	57-72%
L/W Ratio	1.30-1.50	1.20-1.60
Girdle	Thin-Sl. Thick	V.Thin-Thick
Culet	None-V.Small	None-Small

Cushion Cut

Parameter	Ideal	Good
Table %	56-62%	52-67%
Depth %	61-68%	58-72%
L/W Ratio (square)	1.00-1.05	1.00-1.10
L/W Ratio (rect)	1.15-1.25	1.10-1.35
Girdle	Thin-Sl. Thick	V.Thin-Thick

Pear Shape

Parameter	Ideal	Good
Table %	53-63%	50-66%
Depth %	58-62%	56-65%
L/W Ratio	1.50-1.75	1.40-2.00
Girdle	Thin-Sl. Thick	V.Thin-Thick
Bow-Tie	Minimal	Moderate

Marquise Cut

Parameter	Ideal	Good
Table %	53-63%	50-66%
Depth %	58-62%	56-65%
L/W Ratio	1.85-2.10	1.75-2.25
Girdle	Thin-Sl. Thick	V.Thin-Thick
Bow-Tie	Minimal	Moderate

Radiant Cut

Parameter	Ideal	Good
Table %	61-69%	57-72%
Depth %	61-67%	58-72%
L/W Ratio (square)	1.00-1.05	1.00-1.10
L/W Ratio (rect)	1.15-1.35	1.10-1.50

Asscher Cut

Parameter	Ideal	Good
Table %	61-69%	57-72%
Depth %	61-67%	57-72%
L/W Ratio	1.00-1.04	1.00-1.06

Heart Shape

Parameter	Ideal	Good
Table %	53-63%	50-66%
Depth %	58-62%	56-65%
L/W Ratio	0.95-1.05	0.85-1.10

Trillion Cut

Parameter	Ideal	Good
Table %	53-63%	50-66%
Depth %	40-50%	37-55%
L/W Ratio	1.00-1.10	0.95-1.15

How to Use This Chart

1. Find your diamond's shape in the relevant table above
2. Compare its proportions from the certificate against the ranges
3. Ideal range = best possible light performance for that shape
4. Good range = acceptable performance; still a beautiful diamond
5. Outside ranges = proceed with caution; evaluate the stone visually

Important Caveats

• Round brilliants are the only shape that receives an official cut grade from most labs. For all other shapes, use these ranges as guidelines while also evaluating the stone visually.
• Proportions interact — a parameter at the edge of "ideal" range may still produce excellent results if complemented by optimal values in other parameters.
• Visual inspection matters — numbers tell most of the story but not all. When possible, view the diamond in person or through 360° video.
• Personal preference — some buyers prefer the look of a slightly deeper or shallower stone. These ranges define "optimal light performance" but beauty is subjective.

Use this chart alongside our detailed guides on depth and table, crown and pavilion angles, girdle thickness, and culet to become a confident diamond evaluator.

Recommended Pieces

• Ladies Necklace 3 3/4Ct Round/Pear/Marquise 14K Yellow Gold
• Ladies Earrings 1/2Ct Round/Baguette 14K White Gold
• 14K Yellow Gold 2 1/2Ct Round Ladies Ring

Every diamond in our collection falls within the ideal-to-excellent range for its shape — ensuring maximum beauty in every piece.