Two diamonds of the same carat weight can look quite different in size on the hand. Carat is a measure of weight, not of the outline you see when you look down at the ring. The Gemological Institute of America defines one carat as 200 milligrams. How that weight is spread through the stone, and the shape it is cut into, change how large the diamond appears. That is why we always look at the millimetre measurements, and at the stone itself, rather than choosing by the carat number alone.
Weight is not the same as the face up outline
A deeper stone can hide a noticeable amount of weight below the girdle. Face up, it may look smaller than a shallower stone of the same carat. A more elongated oval, pear or marquise spreads its weight along a longer outline, so it can look larger on the finger than a compact stone of the same weight. Our guides to table and depth and to length to width ratio explain those two measurements in more detail.
Shape changes the impression too
A cushion, a round, an oval and a marquise of equal weight will not occupy the same space on the finger. The cut style matters as well. A brilliant cut and a step cut of similar measurements can still feel different, because one breaks the light into many small flashes and the other shows broader flashes across larger facets. None of this makes one shape better than another. It does mean that a carat number, taken on its own, is a poor way to imagine the ring.
How we compare stones for you
When we shortlist diamonds of a similar weight, we set the reports side by side and then look at the stones with you on a video consultation. You can see whether one outline feels more generous, or whether a deeper stone looks a little smaller than its carat suggests. The setting plays a part as well: a halo or side stones will change the presence of the centre. Our guide to the 4Cs explains why carat is only one of the four qualities we consider.
Nothing is made until you approve the design and the stone in writing. A 70 percent deposit is paid then, making time is 5 to 6 weeks, and the ring is UK hallmarked before insured, tracked FedEx delivery. If you would like to compare stones by outline as well as by weight, get in touch or browse the diamonds we can source.
Frequently asked questions
Why can two diamonds of the same carat look different sizes?
Carat is a measure of weight, not of how large a diamond looks face up. Shape, length to width ratio and how deeply the stone is cut all change the outline you see on the hand, even when the weight is the same.
Does a more elongated shape always look larger?
An elongated outline often looks longer on the finger than a compact stone of the same weight, but a very deep stone can hide weight below the girdle and look smaller than its carat suggests. We look at the measurements and at the diamond itself.
Can you tell how large a diamond will look from the carat number alone?
No. The millimetre measurements on the report, and a view of the stone in a setting, tell you more about presence on the hand than the carat figure on its own.
How do you compare stones of the same weight?
We shortlist by the report and then look at the diamonds with you on a video consultation, so you can compare outlines side by side. Nothing is made until you approve the design and the stone in writing.