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A 0.5 carat (half carat) round diamond measures about 5.2 mm across, roughly a fifth of an inch. That is about 80 percent of the width of a 1 carat round, which is 6.5 mm, even though it weighs only half as much.
See a half 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: half a carat is exactly 0.1 grams. How big that weight looks depends on the shape it is cut into. A shape that spreads its weight across the surface measures larger face up. A shape that carries more of its weight in its depth measures smaller.
| Shape | Size at half a carat (length × width) | How it reads |
|---|---|---|
| Round | 5.2 × 5.2 mm | The baseline |
| Marquise | 7.9 × 4.0 mm | Longest for its weight |
| Dutch Marquise | 7.1 × 3.8 mm | Long, six-sided outline |
| Pear | 6.3 × 4.2 mm | Looks larger than a round |
| Oval | 6.1 × 4.5 mm | Looks larger than a round |
| Emerald | 5.6 × 4.0 mm | Slightly longer, slimmer |
| Heart | 5.2 × 5.2 mm | Same width as a round |
| Elongated cushion | 5.0 × 3.8 mm | Slimmer, soft corners |
| Radiant | 5.0 × 3.8 mm | Slimmer, cut corners |
| Princess | 4.4 × 4.4 mm | Compact square |
| Cushion | 4.4 × 4.4 mm | Compact, soft corners |
| Asscher | 4.4 × 4.4 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 0.5 carat lab grown diamond center. For studs, a 1 ct TCW pair gives you half a carat in each ear.
Shown in 14K gold. Every piece is also made in 9K and 18K gold, platinum and 925 silver.
Delicate, bright and unmistakably a diamond. At 5.2 mm across, a half carat round sits neatly on the finger without dominating it.
The most useful thing to know is that width grows far more slowly than weight. Doubling a half carat to 1 carat adds only about 1.3 mm across, from 5.2 to 6.5 mm. Going the other way, a half carat gives you around 80 percent of the width of a 1 carat stone at half the weight, because most of the difference sits in the depth of the stone, where you cannot see it.
On the finger, the eye judges a stone against the width of the finger beside it. A half carat round, 5.2 mm across, covers this much of the finger's width:
| US ring size | Finger width | Width covered by a half carat round |
|---|---|---|
| 5 | 15.7 mm | about 33% |
| 6.5 | 16.9 mm | about 31% |
| 8 | 18.1 mm | about 29% |
That is about a third of the width on a slim finger, so a half carat looks refined rather than small on a size 5 hand, and more understated on a size 8. See a half carat ring on your own ring size.
On the ear, a pair of 0.5 carat studs means half a carat in each ear: each stud is about 5.2 mm across and the pair is 1 carat total weight. If a pair is sold as 0.5 carat total weight, each stud is a quarter carat and about 4.1 mm across. See half carat studs on an ear.
On the neck, a half carat round pendant is the same 5.2 mm stone with the bail above it, a quiet size that suits a fine chain. A half carat pear hung point up measures about 6.3 × 4.2 mm and looks a little longer. See a half carat pendant on a neckline.
Yes, for the right piece. Half a carat is a natural choice for stud earrings, a solitaire pendant, a slim stacking ring or an engagement ring for someone who prefers something understated. At this size the quality of the stone matters more than the weight: a well cut half carat returns light brightly, while a poorly cut one looks glassy whatever it weighs.
Every Ronora diamond is a real CVD lab grown diamond with an Excellent cut, VVS clarity and a D-E-F colorless grade, so choosing half a carat is a choice about size, never about quality. Each piece is made to order by Ronora Diamond in Surat, India.
Elongated shapes. At half a carat, an oval measures about 6.1 × 4.5 mm, a pear about 6.3 × 4.2 mm and a marquise about 7.9 × 4.0 mm, all longer than the 5.2 mm round. That length runs along the finger, which the eye reads as a larger stone.
The setting helps too. A halo of small diamonds around the center blurs its outline, so the eye reads the whole cluster as one larger stone. A hidden halo sits underneath instead and adds sparkle from the side without changing the outline from above. If you prefer a square look, a princess, cushion or Asscher measures about 4.4 mm a side at half a carat and sits compactly.
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.
At half a carat that gap gives you a choice. Some buyers keep the half carat and put the difference into the setting or a matching band. Others use it to move up toward 1 carat for the budget they already had.
A half carat round diamond is about 5.2 mm across. In other shapes, half a carat measures about 6.1 × 4.5 mm as an oval, 4.4 × 4.4 mm as a princess and 7.9 × 4.0 mm as a marquise.
On a US size 6.5 finger, 16.9 mm across, a half carat round covers about 31 percent of the width. It looks refined and bright rather than bold.
For many people, yes. On a US size 5 finger a half carat round covers about 33 percent of the width, which reads as a clear center stone. If you want more presence at the same weight, an oval, pear or marquise measures 6.1 to 7.9 mm long, or you can add a halo.
Yes. A 0.5 carat round stud is about 5.2 mm across, a size that suits everyday wear, and a pair is 1 carat total weight.
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.
The same as at every size: an Excellent cut, VVS clarity and D-E-F colorless. At half a carat, cut quality affects the look far more than a clarity grade either way.
Browse lab grown diamond engagement rings, earrings and pendants, or compare with how big a 1 carat diamond is.
More carat guides: 1 carat, 1.5 carat, 2 carat, 3 carat, 4 carat and 5 carat. To compare every shape side by side, see the diamond size chart.
