Princess Cut Ruby: Pros, Cons & Leakage

Pointed corners and a chevron-patterned pavilion define the princess. Ours is a deep one, 68.5%, carrying 85 facets over a 41.94° pavilion.

In ruby it returns 68 for brilliance, more than the princess in diamond (57) but far less than the T73 in ruby, and over a quarter of the light leaks.

Princess-cut rubies are mostly small calibrated stones for channel and invisible settings, where their straight edges sit flush.

Princess cut ruby: a good idea? Pros and cons

Pros

None by our margins. It is brighter than a diamond princess, but not than a round ruby.

Cons

Less fire than a diamond princess 52 vs 83
Much less light than a round ruby 68 vs 94
More than a quarter of the light leaks 27 vs 5
The heaviest of our square ruby cuts for its width 1.68 vs 1.48 ct

Compared with the T73 Round Brilliant in ruby and with the Princess Cut in diamond. A difference counts from 3 points (Brilliance, Fire, Tilt, Leakage), 5 (Scintillation, Symmetry), 2 (Spread) or 5% (weight); Tilt counts as a pro only for a stone within 5 points of the brilliance it is compared with. How we measure.

All eight scores against the T73

At a glance: the Princess Cut in ruby (white) against the T73 Round Brilliant in ruby (dashed): solid white where it reaches further, hatched where it falls short. Each pro and con is explained, with pictures, below.

Against the T73 Round Brilliant in ruby: ahead on 3, level on 1, behind on 4.

Global71, the comparison 79, difference −8
Brilliance68, the comparison 94, difference −26
Fire52, the comparison 37, difference +15
Scintillation78, the comparison 80, difference −2
Spread95, the comparison 100, difference −5
Symmetry100, the comparison 100, difference 0
Shape-norm106, the comparison 102, difference +4
Tilt76, the comparison 75, difference +1

Face-up light census, a different measure from the Cut Grading Tool; Spread and Shape-norm above 100 sit on the ring.

Open it in the Cut Performance Wheel

What ruby gains in a princess cut

No score beats both baselines. Brilliance, 68, is above the diamond princess's 57 but well below the T73's 94; fire, 52, beats the T73's 37 but trails diamond's 83. Each score counts once, where the gap is larger, so both land as cons. The princess offers the crispest corners of our square-outline cuts.

The princess's costs in ruby

Less fire than a diamond princess

Fire 52 against 83 for the Princess Cut in diamond: 31 points lower

Fire 52 against 83. In ruby the princess still shows more colour than a round does, but corundum's dispersion keeps it well below diamond.

Princess cut in ruby face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 52) — Look at the coloured flashes: those are fire. Same light, same size, same face-up angle; rendered by our 3D Gemstone Simulator from each cut's own model.

Princess cut in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 83) — Look at the coloured flashes: those are fire. Same light, same size, same face-up angle; rendered by our 3D Gemstone Simulator from each cut's own model.

What helps: Chevrons lift fire a little; an elongated Oval Cut Ruby lifts it to 74 in ruby.

Try it yourself: See the fire in the 3D Gemstone Simulator

Much less light than a round ruby

Brilliance 68 against 94 for the T73 Round Brilliant in ruby: 26 points lower

Brilliance 68 against 94, the lowest of our square-outline ruby pages.

Princess cut in ruby face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 68) — Red, green and blue = light returning to the eye; grey = light leaving through the pavilion. This is the head-on view; the Brilliance score averages a wider cone of light, so the score can differ from what one picture shows.

T73 round brilliant in ruby face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 94) — Red, green and blue = light returning to the eye; grey = light leaving through the pavilion. This is the head-on view; the Brilliance score averages a wider cone of light, so the score can differ from what one picture shows.

What helps: For a square-outline ruby with more light, the Cushion Cut Ruby returns 88, the Square Cut Ruby 78.

Try it yourself: Open this Light Return map in the simulator

More than a quarter of the light leaks

Leakage 27 against 5 for the T73 Round Brilliant in ruby: 22 points higher

Our ruby census loses 27% through the pavilion; the T73 loses 5%. The pavilion is at 41.94°, above ruby's 36.4° guide minimum, so a steeper pavilion is not the fix our data points to.

Princess cut in ruby tilted 0 degrees: Light Return map, 27% of the face leaking — Each frame is the Light Return map with the stone tilted away from you by the angle shown; grey is light leaving through the pavilion. The share under each frame is that picture's own.

Princess cut in ruby tilted 10 degrees: Light Return map, 29% of the face leaking — Each frame is the Light Return map with the stone tilted away from you by the angle shown; grey is light leaving through the pavilion. The share under each frame is that picture's own.

What helps: A calibrated 3 mm princess leaks the same share as a 7 mm one; the Cushion Cut Ruby lets out 11%.

Try it yourself: Tilt it yourself in the simulator's light map

The heaviest of our square ruby cuts for its width

1.68 ct at 6.5 mm, against 1.48 ct for the same cut in diamond (+14%)

A 6.5 mm princess is 1.68 ct in ruby: its full corners and 68.5% depth hold a lot of material, and corundum is denser than diamond, where the same stone is 1.48 ct.

A Princess Cut 6.5 mm across, weighed from the model's measured volume and each stone's specific gravity.

What helps: Choose by millimetres, especially for calibrated sets.

Try it yourself: Weights in all seven gemstones on the Princess Cut page

Who a princess ruby suits

The princess suits rubies cut for a line of square stones, where sharp corners must butt together. As a single centre stone, it is the dimmest of our square ruby options. The corners need protecting, usually with V-prongs.

For a square ruby with more light, the Cushion Cut Ruby or the Square Cut Ruby.

In a channel of matched princess rubies, colour consistency across the row usually matters more than any one stone's brilliance, and cutting every stone to the same 41.94° pavilion keeps the row even.

Princess Cut Ruby: questions

Is a princess cut good for ruby?

Not if light comes first: it returns 68 against the T73's 94, and 27% leaks.

Is a princess ruby brighter than a princess diamond?

In our census, yes, 68 to 57: the chevron pavilion suits corundum better than it suits diamond. The diamond keeps the fire, 83 to 52.

What does a 6.5 mm princess ruby weigh?

About 1.68 ct; in diamond, 1.48 ct.

Get the Princess Cut files

6 formatsMillimetresWatertight

Princess Cut 3D files

The Princess Cut as exact geometry: 93 planar facets, real-world scale, ready for CAD, rendering, printing and casting.

STEPExact faceted solid for CAD
3DMRhino, closed mesh on its own layer
STLWatertight mesh for printing and casting
OBJMesh for modelling and rendering
FBXBlender, 3ds Max, Maya, Cinema 4D, Unity, Unreal
GLBWeb, AR and quick previews

€9.99 · Personal useBuy the 3D files

GemCad96 index

Princess Cut cutting files

The Princess Cut as a faceting design: 81 + 4 girdles = 85 facets, 96 index, 4-fold mirror-image symmetry, ready for the machine.

.ascGemCad design file, 96 index gear
.csvTier table: angles, indices and cutting order
DiagramPrintable faceting diagram

€9.99 · Personal useBuy the cutting files

Questions before you buy? Email us.

More gemstones and cuts

Ruby: optical properties and the top ten cuts · The Princess Cut: specifications, model and files

Princess Cut Ruby: crisp square corners, and a quarter of the light lost