Apparent Size

Why two diamonds of the same weight look different in size, and how spread measures it.

Apparent size (spread) shows how large a diamond looks compared with a Tolkowsky round of the same weight.

Diamonds of the same weight can look different in size, depending on their shape. Spread describes this visible size. Positive spread means that the diamond looks larger than a Tolkowsky round of the same weight. Negative spread means that it looks smaller.

Apparent size of a 1 ct Marquise

A 1.00 ct Marquise next to a 1.00 ct Round

A round with the same face-up area as this Marquise weighs 1.29 ct.

The Marquise next to a 1.29 ct round with the same face-up area

Absolute apparent size (spread) shows how much heavier or lighter a round with the same face-up area is.

A round with the same face-up area is 0.29 ct heavier than this 1.0 ct Marquise.

The absolute apparent size depends on the weight of the diamond.

Marquise absolute spread: 1.29 ct minus 1.00 ct equals +0.29 ct

Relative apparent size shows the weight ratio between the diamond and a round with the same face-up area.

A round with the same face-up area is 22% heavier than this Marquise.

The relative apparent size does not depend on the weight of the diamond.

Marquise relative spread: 1 minus 1.00 ct divided by 1.29 ct equals +22%

Apparent size of a 1 ct Cushion

A 1.00 ct Cushion next to the Marquise and the Round

A round with the same face-up area as this Cushion weighs 0.78 ct.

The Cushion next to a 0.78 ct round with the same face-up area

Cushion absolute spread: 0.78 ct minus 1.00 ct equals -0.22 ct

Cushion relative spread: 1 minus 1.00 ct divided by 0.78 ct equals -28%

In practice

Use the relative apparent size to compare diamonds of different weights, because it does not depend on weight.

See also Optical Performance Evaluation.