What is the length-to-width ratio of a diamond?

The length-to-width ratio measures how much longer a fancy-shape lab-grown diamond is than it is wide, expressed as a single number. It applies only to non-round shapes like marquise, oval, pear, emerald and cushion, and has no meaning for round brilliants. IGI grading reports record this figure, allowing you to verify exact proportions before buying, but no single ratio is objectively correct. Preference drives the choice entirely. A marquise, for instance, has a commonly cited range of 1.70 to 2.05, yet buyers consistently gravitate toward 1.80 when comparing stones side by side, despite being told 2.00 is the standard. Some prefer a wider, fuller marquise at 1.60 and others want a narrow, elongated silhouette closer to 2.25. Neither is wrong. The same principle holds across other fancy shapes: an oval or pear can read very differently depending on whether its ratio sits at the compact or elongated end of its typical range, and both readings are equally valid. When shopping for a fancy-shape lab-grown diamond, use the ratio as a filter to shortlist shapes that match your visual preference. Because lab-grown diamonds are available across a wide range of proportions, finding the precise outline you want is far more achievable than it once was with mined stones.