Diamond Carat Size Chart: Millimetres by Shape and Weight
Reference dimensions for round, oval and emerald cut diamonds at 1ct, 1.5ct and 2ct — a quick way to check whether a specific stone has good spread.
Carat weight alone doesn't tell you how large a diamond will actually look — millimetre dimensions do. Use this as a reference point when comparing a specific stone's certificate against what's typical for its shape and weight.
Round brilliant
| Carat | Diameter |
|---|---|
| 1.0ct | ≈6.5mm |
| 1.5ct | ≈7.3mm |
| 2.0ct | ≈8.1mm |
Oval
| Carat | Length × Width |
|---|---|
| 1.0ct | ≈7.7mm × 5.7mm |
| 1.5ct | ≈8.5mm × 6.5mm |
| 2.0ct | ≈9.0mm × 7.0mm |
Emerald cut
| Carat | Length × Width |
|---|---|
| 1.0ct | ≈7.0mm × 5.0mm |
| 1.5ct | ≈7.5mm × 5.5mm |
| 2.0ct | ≈8.5mm × 6.5mm |
How to use this table
Compare a specific stone's certificate dimensions against the typical figures above for its shape and carat weight. A stone measuring notably smaller than typical has been cut deep, prioritising weight retention over face-up size — see our diamond spread guide for what that trade-off means in practice. A stone measuring at or above the typical figure has good spread and will wear larger than its carat weight alone suggests.
A reminder on what these numbers don't capture
Two stones with identical dimensions can still look different face-up depending on cut quality, faceting style (see our crushed ice vs faceted guide) and how well the stone returns light (see our windowing and extinction guide). Dimensions are a useful first filter, not the whole picture.
Related reading
- Which diamond shape looks biggest for its carat weight?
- 1 carat vs 1.5 carat diamond compared
- 1.5 carat vs 2 carat diamond compared
Source: dimension figures consolidated from current trade-jeweller size-chart references (VRAI, BlueStone, Estate Diamond Jewelry) — treat as typical/approximate, since exact dimensions vary stone to stone even within a shape and carat weight.
1 Carat vs 1.5 Carat Diamond: Size, Price & Look Compared
A 1.5ct round diamond is only around 12% wider than a 1ct, not 50% bigger — what actually changes in size, price and everyday look.
1.5 Carat vs 2 Carat Diamond: Size, Price & Look Compared
A 2ct round diamond covers roughly 50% of an average finger's width versus 45% at 1.5ct — a genuinely noticeable step up, at a real price jump.
Which Diamond Shape Looks Biggest for Its Carat Weight?
Elongated shapes spread more surface area across the finger than round does for the same carat weight — which ones give you the most visible size.
Compare real stones before you commit
Use Chaos to understand certificates, pricing, availability and dealer supply before asking for a specific stone.