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A 1.5 carat round diamond measures about 7.4 mm across, roughly three tenths of an inch. That is about 0.9 mm wider than a 1 carat round at 6.5 mm and about 0.8 mm narrower than a 2 carat at 8.2 mm, which places it neatly between a classic and a statement center stone.
See a 1.5 carat diamond at actual size on your own finger, ear or neck with Find Me Diamond, Ronora's free diamond size visualizer.
Carat is a measure of weight, not size: 1.5 carats is exactly 0.3 grams. How big that weight looks depends on the shape it is cut into. Shapes that spread their weight across the surface measure longer face up, while shapes that carry more weight in their depth measure smaller.
| Shape | Size at 1.5 carats (length × width) | How it reads |
|---|---|---|
| Round | 7.4 × 7.4 mm | The baseline |
| Marquise | 11.4 × 5.7 mm | Longest for its weight |
| Dutch Marquise | 10.3 × 5.6 mm | Long, six-sided outline |
| Pear | 9.1 × 6.1 mm | Looks larger than a round |
| Oval | 8.8 × 6.5 mm | Looks larger than a round |
| Emerald | 8.0 × 5.7 mm | Slightly longer, slimmer |
| Heart | 7.4 × 7.4 mm | Same width as a round |
| Elongated cushion | 7.1 × 5.5 mm | Slimmer, soft corners |
| Radiant | 7.1 × 5.5 mm | Slimmer, cut corners |
| Princess | 6.3 × 6.3 mm | Compact square |
| Cushion | 6.3 × 6.3 mm | Compact, soft corners |
| Asscher | 6.3 × 6.3 mm | Compact square, step cut |
These are typical face-up sizes for well proportioned stones at the classic ratio for each shape. A real stone can differ by a few tenths of a millimeter depending on how deep it is cut.
Each ring below can be made with a 1.5 carat lab grown diamond center, D-E-F colorless with VVS-VS clarity. For studs, a 3 ct TCW pair is 1.5 ct in each ear.
Shown in 14K gold. Every piece is also made in 9K and 18K gold, platinum and 925 silver.
Fuller than a 1 carat, but not by as much as the numbers suggest. A 1.5 carat stone weighs 50 percent more than a 1 carat, yet a round measures only about 14 percent wider, because the extra weight is spread through all three dimensions, including depth you cannot see from above.
What you do see is a stone with a little more presence. It fills more of the finger and reads clearly as a center stone at arm's length, while on most hands it still looks refined rather than bold.
On the finger, the eye judges a stone against the width of the finger beside it. A 1.5 carat round, 7.4 mm across, covers this much of the finger's width:
| US ring size | Finger width | Width covered by a 1.5 carat round |
|---|---|---|
| 5 | 15.7 mm | about 47% |
| 6.5 | 16.9 mm | about 44% |
| 8 | 18.1 mm | about 41% |
On a size 5 finger a 1.5 carat round covers close to half the finger's width; on a size 8 it covers about two fifths. See a 1.5 carat ring on your own ring size.
On the ear, a pair of 1.5 carat studs means one and a half carats in each ear: each stud is about 7.4 mm across and the pair is 3 carats total weight. If a pair is sold as 1.5 carats total weight, each stud is 0.75 carat and about 5.9 mm across. See 1.5 carat studs on an ear.
On the neck, a 1.5 carat round pendant is the same 7.4 mm stone with the bail above it. A 1.5 carat pear hung point up measures about 9.1 × 6.1 mm and looks a little longer. See a 1.5 carat pendant on a neckline.
Elongated shapes. At 1.5 carats a marquise measures about 11.4 × 5.7 mm, a pear about 9.1 × 6.1 mm and an oval about 8.8 × 6.5 mm, all longer than the 7.4 mm round. That length runs along the finger, which the eye reads as a larger stone.
An oval is a balanced middle ground. It is narrower across the finger than a round, covering about 39 percent of the width of a US size 6.5 finger against 44 percent for the round, while running 8.8 mm along it. If you prefer a square outline, a princess, cushion or Asscher measures about 6.3 mm a side and sits more compactly.
If you want more presence than a 1 carat without the scale of a 2 carat, it usually is. The step from 1 to 1.5 carats adds about 0.9 mm across a round, a difference you can see on the hand, especially side by side.
A lab grown diamond typically costs 60 to 80 percent less than a mined diamond of the same carat, cut, clarity and color. They are the same material with the same hardness and optical properties, so the difference is origin and rarity rather than quality. In practice that makes the move from 1 to 1.5 carats far gentler in lab grown than the same step in mined.
Whatever size you choose, Ronora sets every center stone with an Excellent cut, VVS clarity and D-E-F colorless, and every lab grown diamond center stone of 1 carat and above ships with an IGI certificate. Each piece is CVD lab grown diamond jewelry made to order by Ronora Diamond in Surat, India.
A 1.5 carat round diamond is about 7.4 mm across. In other shapes, 1.5 carats measures about 8.8 × 6.5 mm as an oval, 6.3 × 6.3 mm as a princess and 8.0 × 5.7 mm as an emerald.
It is a generous, confident size without being oversized. A 1.5 carat round covers about 44 percent of the width of a US size 6.5 finger, against about 38 percent for a 1 carat and 48 percent for a 2 carat.
On a US size 5 finger, 15.7 mm across, a 1.5 carat round covers about 47 percent of the width. On a size 8 finger, 18.1 mm across, it covers about 41 percent, so it looks a little more understated on a larger hand.
A 1.5 carat oval measures about 8.8 × 6.5 mm. Set lengthwise, it runs 8.8 mm along the finger and covers about 39 percent of the width of a US size 6.5 finger, so it looks longer and slimmer than a round of the same weight.
Each 1.5 carat round stud is about 7.4 mm across, and the pair is 3 carats total weight. A pair sold as 1.5 carats total weight has 0.75 carat in each ear, about 5.9 mm per stud.
At Ronora, yes. Every lab grown diamond center stone of 1 carat and above ships with an IGI certificate and a laser-inscribed report number on the girdle.
Yes. It is carbon in the same crystal structure, with the same hardness and optical properties as a mined diamond, so it measures the same size as a mined diamond of the same carat weight and cut.
Browse lab grown diamond engagement rings, or compare with how big a 1 carat diamond is and how big a 2 carat diamond is.
More carat guides: half carat, 1 carat, 2 carat, 3 carat, 4 carat and 5 carat. To compare every shape side by side, see the diamond size chart.
