The modernsquare, sized.Carat to millimetres.
A crisp square with brilliant faceting, the princess is measured by its side length in millimetres. This chart converts each carat to real dimensions from our own stones.
Why carat isn't the same as size.
Carat measures weight, not dimensions. The size you actually see is the stone's measurement in millimetres — and two diamonds of the same carat can look different sizes depending on how they are cut.
A shallow, well-spread stone shows more face-up area; a deep-cut one hides weight underneath. So when comparing diamonds, compare the millimetre dimensions, not just the carat weight.
"The number that decides how big a diamond looks isn't the carat — it's the measurement in millimetres."
The chart below gives you both, so you can picture the real size before you choose.
What makes the princess special.
The princess pairs a sharp square shape with brilliant faceting — the most sparkle of any square cut.
Its squared shape retains more of the rough, so a princess often costs a little less per carat than a round.
Sharp corners are the vulnerable point — a setting that covers them prevents chipping.
Brilliant faceting masks small inclusions, so eye-clean VS stones are easy to find.
What each size actually looks like.
These princess shapes are drawn to relative scale from real face-up dimensions. Notice how gently size grows — a 2 carat is larger than a 1 carat, but not twice the size.
Drawn to relative scale for a well-cut princess. On-screen sizes are proportional, not literal millimetres — see the chart below for exact dimensions.
Princess Cut carat to millimetre chart.
Approximate face-up dimensions for a well-cut princess. Sizes marked "Measured" reflect our own diamond measurements; larger sizes are extrapolated to the same proportions. Individual stones vary with cut and depth.
| Carat Weight | Size (mm) | L/W Ratio | Source |
|---|---|---|---|
| 0.25 ct | 3.5 mm | 1.00 | Measured |
| 0.50 ct | 4.4 mm | 1.00 | Measured |
| 0.75 ct | 5.0 mm | 1.00 | Measured |
| 1.00 ct | 5.5 mm | 1.00 | Measured |
| 1.25 ct | 5.9 mm | 1.00 | Approx. |
| 1.50 ct | 6.3 mm | 1.00 | Approx. |
| 1.75 ct | 6.6 mm | 1.00 | Approx. |
| 2.00 ct | 6.9 mm | 1.00 | Approx. |
| 2.50 ct | 7.5 mm | 1.00 | Approx. |
| 3.00 ct | 7.9 mm | 1.00 | Approx. |
| 4.00 ct | 8.7 mm | 1.00 | Approx. |
| 5.00 ct | 9.4 mm | 1.00 | Approx. |
Choosing the right proportions.
Two princesss of the same carat can look different depending on their length-to-width ratio. It comes down to taste — here are the main looks.
The classic princess — equal sides, sharp and contemporary.
Barely perceptible length — still reads as a clean square.
A subtle rectangle for those who want a hint of length.
Four things worth knowing first.
Beyond size, a few princess-specific pointers help you choose a stone that looks its best.
Pointed corners can chip, so choose a setting with protective prongs or a channel — the one real durability consideration.
Faceting hides inclusions, so an eye-clean VS1–VS2 looks flawless at good value.
A little warmth can gather in the corners; near-colourless grades keep it crisp in white metal.
A ratio at or just above 1.00 gives the clean, classic princess look most buyers want.
How the setting changes the size you see.
The same stone can look bigger or smaller depending on how it is set. If maximising visual size matters, the setting is as important as the carat weight.
A solitaire shows the true size; a halo frames it to read larger; a three-stone setting stretches the look along the finger. Choosing well means you can often get the presence you want without moving up in carat.
Browse princess diamonds by size.
Found your size? Go straight to the collection — every stone IGI certified and lab grown.
Princess size questions, answered.
The questions we hear most about princess diamond sizing. If yours isn't here, just ask.
Chat on WhatsAppCompare sizes across every shape.
Still choosing a shape? Compare all cuts side by side →
Everything you need to choose with confidence.
Find your perfect princess.
Every princess is IGI certified and made to order, in the exact carat, ratio, and setting you choose. Not sure which size suits the hand? Tell us and we'll guide you.