The princess cut diamond is a modern classic in the jewelry world, beloved for its sharp square shape, brilliant sparkle, and contemporary style. If you’re choosing a princess cut diamond for an engagement ring or fine jewelry, understanding how millimeter dimensions (mm) translate to carat weight is essential.
While carat weight measures the diamond’s mass, the size in millimeters tells you how big it will actually appear on the finger. Two princess cut diamonds with the same carat weight can look slightly different in size depending on depth and table percentages.
This guide provides a combined mm-to-carat and carat-to-mm chart so you can make informed decisions about size, budget, and appearance.
📐 Why Size Can Vary in Princess Cut Diamonds
Princess cuts are square or slightly rectangular with sharp, pointed corners and a faceting style that maximizes fire and brilliance.
Two main factors affect size appearance:
-
Depth percentage – A deeper stone may weigh more without looking larger from above.
-
Table percentage – A larger table can make a diamond appear bigger.
| MM (Length × Width) | Approx. Carat Weight | Carat Weight | Approx. MM Size |
|---|---|---|---|
| 4.0 × 4.0 mm | 0.30 ct | 0.30 ct | 4.0 mm |
| 4.5 × 4.5 mm | 0.50 ct | 0.50 ct | 4.5 mm |
| 5.0 × 5.0 mm | 0.75 ct | 0.75 ct | 5.0 mm |
| 5.5 × 5.5 mm | 1.00 ct | 1.00 ct | 5.5 mm |
| 6.0 × 6.0 mm | 1.25 ct | 1.25 ct | 6.0 mm |
| 6.5 × 6.5 mm | 1.50 ct | 1.50 ct | 6.5 mm |
| 7.0 × 7.0 mm | 2.00 ct | 2.00 ct | 7.0 mm |
| 7.5 × 7.5 mm | 2.50 ct | 2.50 ct | 7.5 mm |
| 8.0 × 8.0 mm | 3.00 ct | 3.00 ct | 8.0 mm |
| 8.5 × 8.5 mm | 3.50 ct | 3.50 ct | 8.5 mm |
| 9.0 × 9.0 mm | 4.00 ct | 4.00 ct | 9.0 mm |
Note: Sizes are averages; actual dimensions vary with cut quality and depth percentage.
💡 Tips for Choosing the Right Princess Cut Size
-
Finger size matters – Smaller fingers make diamonds appear larger, while larger fingers might need more spread for the same visual effect.
-
Consider setting protection – Princess cut corners are delicate; a V-prong or bezel setting can protect them without sacrificing beauty.
-
Budget smart – Choosing just under a "magic weight" (e.g., 0.95 ct instead of 1.00 ct) can save you 10–20% with almost no visible size loss.
-
Look beyond carat weight – A well-cut 1.00 ct diamond with excellent proportions will look larger than a poorly cut 1.10 ct stone.
Understanding the Princess Cut Diamond Size Chart ensures you get the most beauty for your budget. By knowing the mm-to-carat relationship, you can confidently choose a diamond that fits your style, finger size, and price range. Whether for an engagement ring, anniversary gift, or luxury upgrade, size knowledge is your best tool for finding the perfect princess cut diamond.
