Carat Size Tool
How big is a diamond, really?
Carat is a measure of weight, not size. Compare six shapes at true scale, and calibrate the tool to your own screen to see a stone at its real millimetre size.
- Carat
- 1.00ct
- Length
- 6.30mm
- Width
- 6.30mm
Approximate size
Sizes are to scale against one another. Calibrate your screen to see the stone at approximately actual size.
·
Hold a bank card flat against the screen and drag the slider until the outline matches it exactly. Every card is 85.60 mm wide, which is how the page learns the size of a millimetre on your device.
·
Why two diamonds of the same weight look different
A diamond may carry more of its weight in its depth, which makes it face up smaller than its carat weight suggests. Another stone of identical weight may have a wider visible spread. Shape matters too: elongated ovals, pears and marquises often appear larger than a round diamond of equivalent weight, because more of the stone is visible from above.
This is why I compare millimetre measurements alongside carat weight. Two 1.00ct rounds can differ by a third of a millimetre across the table — small on paper, visible on a hand.
The figures used here are for well-cut stones. A poorly proportioned diamond of the same weight can measure noticeably smaller face up, which is one of the reasons cut quality matters more than the carat figure alone.
Not sure which size is right for you?
I help clients weigh size against cut, colour and budget — and see stones in person or on video before deciding.