Princess Cut Diamonds: buyer checklist
The princess cut is a square outline with brilliant faceting — geometric and modern from above, with the fire of a round brilliant. It is the most popular square shape and consistently one of the best-value cuts available, because a square maps efficiently onto the natural octahedral form of rough diamond. Far less material is lost than in cutting a round, and that saving passes to the buyer.
Two things govern buying one well. The corners are the stone’s structural weak point and must be protected. And princess cuts are cut deep more often than almost any other shape, which means carat weight is a poor guide to how large the stone will look.
This page is about choosing the stone. For settings and finished rings, see princess cut diamond rings.
- Check depth percentage and compare millimetre spread, not carat weight.
- Check the outline is genuinely square and the corners match.
- Check the clarity plot for anything near a corner.
- Look for colour concentrating in the corners.
- Confirm the setting will cover all four corners before buying the stone.
The main options to compare
Square or slightly rectangular
Most princess cuts are close to square, with a length-to-width ratio near 1.00. Ratios up to about 1.10 still read as square to the eye; beyond that the stone starts to look deliberately rectangular. Decide which you want and specify it, since both are sold under the same name.
Origin
Natural or laboratory-grown — the largest single price influence. Both are diamond, graded identically, and origin must be stated on the report. See lab-grown vs natural diamond.
Alternatives worth weighing
If the corner vulnerability concerns you, two shapes give a similar geometric look without sharp corners. The cushion has rounded corners and a softer character. The radiant has cropped corners and similar brilliance — see radiant cut diamond rings. Compare all outlines at diamond shapes.
Quality and practical factors: cut quality, corner protection, symmetry and setting security
Depth, and the size problem
This is the princess cut’s main pitfall. The shape is often cut deep to retain as much weight as possible from the rough, which means a substantial portion of the carat weight sits below the girdle where it contributes nothing to how the stone looks. A deep princess cut can appear noticeably smaller than another stone of the same weight.
Check the depth percentage on the report, and always compare candidates on millimetre measurements rather than carat weight. In this shape that single check is worth real money.
Corner protection
The four corners are the thinnest, most exposed part of a princess cut and the place where chips occur. A chipped corner generally cannot be repaired without recutting the entire stone, so this is a durability matter rather than a cosmetic one.
The standard solution is a four-prong setting where each prong sits directly over a corner — the same prongs that hold the stone also shield its weak points. Ask specifically that the prongs cover the corners rather than the sides, because both arrangements exist and only one protects the stone. A bezel is the most protective option of all.
Ask also whether any corner shows an existing chip or abrasion, and check girdle thickness at the corners on the report — an extremely thin girdle there is a genuine concern.
Symmetry
Geometric shapes are unforgiving of asymmetry. The four sides should be equal, the corners should match one another in angle, and the outline should read as a true square rather than a slightly skewed one. Irregularity that would be invisible in a curved shape is obvious here.
Colour and clarity behaviour
Body colour tends to concentrate in the corners of a princess cut, so a warm tint can be more apparent than the grade alone suggests — worth a grade more if you are setting in platinum or white gold, and irrelevant in yellow or rose gold.
Clarity is reasonably forgiving, since the brilliant faceting disguises small inclusions. But check the plot specifically for anything near a corner: an inclusion there compounds an area that is already structurally the weakest part of the stone, which is a durability question as well as an appearance one.
Price and budget considerations
- Princess cuts cost less per carat than round brilliants, and by a useful margin. The efficient use of rough is the shape’s core financial advantage.
- Diamond origin — the largest lever in any shape.
- Carat thresholds — buying just under a round weight is still the most reliable saving available.
- Watch depth rather than chasing weight. A shallower, well-spread princess cut at a lower carat weight will often look larger than a deeper stone costing more. This is the shape’s biggest hidden saving.
- Clarity — an easy saving, subject to the corner check.
- Colour — hold a grade for white metal, or drop it deliberately with warm metal.
- Do not economise on the setting. This is the one shape where a cheap mount genuinely risks losing the stone.
See diamond price South Africa. Quotes are dated and specification-based.
Certification, documentation and trust checks
Graded on the four characteristics in GIA’s grading methodology, with report types set out in GIA’s guide to report types.
- No overall cut grade is issued for princess cuts. Read polish, symmetry and the proportion figures, and treat depth percentage as the number that matters most in this shape.
- Verify the report number on the issuing laboratory’s own database, and check the measurements match the stone.
- Read the origin and treatment lines.
- Study the clarity plot with the corners in mind.
- Check girdle thickness, particularly at the corners.
- Note which laboratory issued it — strictness varies, and identical letters are not equivalent across laboratories. See diamond certificate explained.
Why princess cuts are so often cut deep
Understanding the reason helps you spot it. Rough diamond commonly forms as an octahedron — two square-based pyramids joined at the base. A princess cut maps onto that form efficiently, and in fact two princess cuts can often be cut from a single octahedron with relatively little waste, where cutting a round from the same rough would sacrifice a great deal more.
That efficiency is the shape’s advantage, and it is why princess cuts cost less per carat. But it also creates a temptation: because the cutter is being paid for weight, there is a strong incentive to retain as much of the pyramid’s depth as possible rather than trimming to optimal proportions. The result is a stone that weighs what the report says and looks smaller than it should from above.
This is not dishonest, and the depth is recorded on the report for anyone who reads it. But it does mean that in this shape more than most, carat weight and visible size come apart. Comparing millimetre measurements across several candidates at the same weight will usually reveal a noticeable spread — and the widest one at the same price is simply the better buy.
Common mistakes to avoid
- Buying on carat weight. Because deep cutting is so common in this shape, weight is an unusually poor predictor of visible size. Compare millimetres.
- Accepting a setting that leaves corners exposed. The most consequential mistake here, and the one that ends with a chipped stone.
- Ignoring an inclusion near a corner because the overall clarity grade looks acceptable.
- Assuming all princess cuts are square. Many are noticeably rectangular; check the ratio.
- Overlooking corner colour when setting in white metal.
- Choosing this shape for very hands-on work without opting for a bezel. A cushion or radiant would serve better.
Choosing the stone with the setting already in mind
In most shapes you can choose a stone and decide the setting afterwards. In a princess cut the two decisions are linked, because corner protection is a structural requirement rather than a style preference, and it should influence which stone you buy.
If you already know the ring will be bezel-set, you have more latitude: the bezel encloses the corners completely, so a stone with a slightly thinner girdle at the corners or a small inclusion near one becomes acceptable, and you can take the saving.
If the ring will be a four-prong solitaire, the corners carry more exposure and you should be correspondingly stricter — avoid stones with inclusions near a corner or an unusually thin girdle there, because the setting will not compensate.
Tell whoever is showing you stones which setting you intend before you start looking. It changes which stones are suitable, and it is a great deal cheaper to know at that point than after the stone is bought.
Next step: narrow the shortlist and enquire
Set your origin, ratio and budget, then ask to see princess cuts with their depth percentages and millimetre measurements alongside the carat weights. Compare the face-up sizes directly — you will often find a lighter stone that looks bigger and costs less. Then settle the setting before you commit, because corner protection should influence which stone you buy.
Move to settings at princess cut diamond rings, or compare outlines at diamond shapes. For the whole process, the diamond buying guide.
Continue to the relevant buying guide or book expert guidance
Tell us the size and budget you have in mind and what the wearer does with their hands. We will show princess cuts compared on face-up spread rather than weight, flag any inclusion sitting near a corner, and recommend a setting that genuinely shields all four corners.