The boat cut,at every size.Carat to millimetres.
Long, pointed and dramatic, the marquise is measured length × width 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 marquise special.
Its long, narrow outline gives the marquise the biggest face-up area of any shape for its weight.
No shape lengthens and slims the finger more — the marquise is the most elongating cut of all.
Both ends are pointed and vulnerable; V-prongs shield them from chipping.
Like other elongated brilliants, a marquise can show a bow-tie; good symmetry keeps it faint.
What each size actually looks like.
These marquise 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 marquise. On-screen sizes are proportional, not literal millimetres — see the chart below for exact dimensions.
Marquise Cut carat to millimetre chart.
Approximate face-up dimensions for a well-cut marquise. 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 | 6.5 × 3.3 mm | 1.94 | Measured |
| 0.50 ct | 8.2 × 4.2 mm | 1.94 | Measured |
| 0.75 ct | 9.4 × 4.8 mm | 1.94 | Approx. |
| 1.00 ct | 10.3 × 5.3 mm | 1.94 | Approx. |
| 1.25 ct | 11.1 × 5.7 mm | 1.94 | Approx. |
| 1.50 ct | 11.8 × 6.1 mm | 1.94 | Approx. |
| 1.75 ct | 12.4 × 6.4 mm | 1.94 | Approx. |
| 2.00 ct | 13.0 × 6.7 mm | 1.94 | Approx. |
| 2.50 ct | 14.0 × 7.2 mm | 1.94 | Approx. |
| 3.00 ct | 14.9 × 7.6 mm | 1.94 | Approx. |
| 4.00 ct | 16.4 × 8.4 mm | 1.94 | Approx. |
| 5.00 ct | 17.6 × 9.1 mm | 1.94 | Approx. |
Choosing the right proportions.
Two marquises of the same carat can look different depending on their length-to-width ratio. It comes down to taste — here are the main looks.
A slightly broader marquise — a touch less pointed, still striking.
The balanced, most classic marquise — neither too narrow nor too wide.
A longer, more slender boat for the most dramatic, elongating look.
Four things worth knowing first.
Beyond size, a few marquise-specific pointers help you choose a stone that looks its best.
V-prongs at each tip guard the marquise's two vulnerable points and define its crisp outline.
The two halves must mirror each other and the points must align — uneven symmetry is very visible on a marquise.
Warmth concentrates at the tips; a slightly higher colour grade keeps them bright in white metal.
Brilliant faceting hides small inclusions, so an eye-clean VS stone offers great value.
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 marquise diamonds by size.
Found your size? Go straight to the collection — every stone IGI certified and lab grown.
Marquise size questions, answered.
The questions we hear most about marquise 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 marquise.
Every marquise 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.