Diamond Shapes & Size Chart
Visual guide to diamond shapes with millimetre-to-carat weight conversions. Select a shape to view the full size reference table.
Understanding Diamond Sizes
Diamond size is commonly expressed in carat weight, but the face-up appearance depends on its millimetre dimensions. Two diamonds of the same carat weight can appear quite different in size depending on how they are cut — a well-cut diamond will have optimal proportions that maximise its visual spread.
The measurements in this chart are approximate averages for well-proportioned diamonds of each shape. Actual dimensions vary based on cut quality, depth percentage, and individual stone characteristics. For elongated shapes like oval, pear, and marquise, dimensions are given as length × width.
Choosing the Right Shape
Round brilliant diamonds offer the most sparkle due to their mathematically optimised 57-facet arrangement. Step-cut shapes like emerald and asscher emphasise clarity with open, mirror-like facets — inclusions are more visible, so higher clarity grades are recommended. Fancy shapes like oval, pear, and marquise can appear up to 15% larger face-up than a round of the same weight, making them an excellent value choice.
Cushion and radiant cuts offer a balance between the fire of a round and the elegance of a rectangular outline, with large facets that produce dramatic flashes of light. Heart shapes require masterful cutting to achieve proper symmetry and are most effective above 0.50 carats where the shape is clearly visible.
Diamond MM Size for Calibrated Stones
For pavé, channel, and cluster settings, jewellers use calibrated diamonds — stones cut to precise millimetre dimensions. Common calibrated sizes include 1.0 mm, 1.3 mm, 1.5 mm, 1.8 mm, 2.0 mm, and 2.5 mm rounds. Consistency in size is critical for a clean, uniform look in finished jewellery.
Need Help?
Our gemologists and jewellers can help you select the perfect diamond shape and size for your project. Whether you need calibrated melee for pavé settings or a centre stone for a bespoke engagement ring, Casa Jewels sources diamonds directly to ensure quality and competitive pricing. Get in touch →