Lab Grown Diamond Size Chart
Every shape,every size.Carat to millimetres.
Carat is weight, not size — the size you see is the stone's measurement in millimetres. Choose a shape below for its full carat-to-mm chart, ideal length-to-width ratios, and sizing advice, all built from our own diamond measurements.
Carat is weight. Millimetres are size.
The single most useful thing to understand when choosing a diamond: carat measures how much a stone weighs, not how big it looks. The size your eye sees is the measurement across the top, in millimetres.
That is why shape matters so much. An elongated shape like a marquise or oval spreads its weight over a longer surface and looks larger than a compact shape of the same carat. Two diamonds can weigh exactly the same and look noticeably different sizes.
"Compare diamonds by their millimetres, not just their carats — that's what you actually see on the hand."
Pick a shape below for its detailed chart, or use the quick overview to compare every shape at a glance.
Every shape, compared by size.
Approximate face-up dimensions at popular carat weights. Tap any shape for its full chart and sizing guide.
| Shape | 0.5 ct | 1 ct | 1.5 ct | 2 ct | 3 ct |
|---|---|---|---|---|---|
| Round → | 5.2 mm | 6.5 mm | 7.4 mm | 8.2 mm | 9.4 mm |
| Oval Cut → | 6.3 × 4.4 mm | 8.0 × 5.6 mm | 9.2 × 6.4 mm | 10.1 × 7.1 mm | 11.5 × 8.1 mm |
| Pear Cut → | 6.7 × 4.3 mm | 8.4 × 5.4 mm | 9.6 × 6.2 mm | 10.6 × 6.8 mm | 12.1 × 7.8 mm |
| Emerald Cut → | 5.3 × 3.8 mm | 6.7 × 4.8 mm | 7.7 × 5.5 mm | 8.4 × 6.0 mm | 9.7 × 6.9 mm |
| Radiant Cut → | 5.3 × 3.8 mm | 6.7 × 4.8 mm | 7.7 × 5.5 mm | 8.4 × 6.0 mm | 9.7 × 6.9 mm |
| Cushion Cut → | 4.5 mm | 5.7 mm | 6.5 mm | 7.2 mm | 8.2 mm |
| Princess Cut → | 4.4 mm | 5.5 mm | 6.3 mm | 6.9 mm | 7.9 mm |
| Marquise Cut → | 8.2 × 4.2 mm | 10.3 × 5.3 mm | 11.8 × 6.1 mm | 13.0 × 6.7 mm | 14.9 × 7.6 mm |
| Heart Cut → | 5.5 × 5.1 mm | 6.9 × 6.4 mm | 7.9 × 7.3 mm | 8.7 × 8.1 mm | 10.0 × 9.2 mm |
Round is shown as diameter; all others as length × width. Figures are approximate for well-cut stones.
Size charts for every diamond shape.
Each guide has a full carat-to-millimetre chart, a to-scale visual, ideal length-to-width ratios, and shape-specific buying advice.
Still choosing a shape? Compare all cuts side by side →
Reading a size chart the right way.
Two stones of the same carat can look different sizes. The millimetre dimensions tell you how large a diamond actually appears face-up — always the number to compare.
For elongated shapes, the length-to-width ratio changes the whole look for the same carat. Each shape guide shows the ratios and what they mean.
A halo or slim band can make a stone read larger. The setting matters as much as the carat — see our setting guide for how to maximise presence.
Sizes up to 1 carat reflect our own diamond measurements; larger sizes are extrapolated. Every stone's exact dimensions are on its IGI certificate.
Everything you need to choose with confidence.
We'll help you find the right size.
Tell us the shape and the hand, and we'll recommend a carat and setting that looks right — every diamond IGI certified and made to order.