Diamond guide
Light, certified.
Everything that decides how a diamond looks and what it is worth, explained plainly, so you can choose with the same confidence as the people who grade them.
Diamond education
The four Cs
Cut, colour, clarity and carat: the language every diamond is described in. Here is what each one means for the stone you choose.
Cut decides the sparkle.
A well-cut diamond returns the light that enters it through the top, as brilliance and fire. It is the only one of the four Cs shaped by human hands, so it is where we never compromise: our round brilliants are Excellent or Ideal.
Shapes
Ten ways to cut light
- roundThe most brilliant cut, and the classic for solitaires.
- ovalElongates the finger and looks larger for its weight.
- princessSquare and crisp, with a modern sparkle.
- cushionSoft corners and a romantic, antique glow.
- emeraldLong step facets that show clarity like a hall of mirrors.
- pearPart round, part marquise: graceful on the hand.
- marquiseThe longest outline of all, for the most finger coverage.
- radiantA rectangle with the fire of a brilliant cut.
- asscherA square step cut with an Art Deco feel.
- heartUnmistakable, and the most demanding to cut well.
Certificates
Graded by an independent lab
- GIA and IGIOur centre diamonds are graded by the Gemological Institute of America or the International Gemological Institute, never by us.
- Check it yourselfEach product page links to the lab’s report checker. The report number is also laser-inscribed on the stone’s girdle, visible under a loupe.
Ring sizes
Find your size
With a ring that fits
Lay it on a ruler and measure the inside diameter, edge to edge, in millimetres. Find the closest diameter in the table.
With a strip of paper or thread
- Wrap it around the base of the finger, snug but able to slide over the knuckle.
- Mark where it overlaps, then measure the length in millimetres: that is the circumference (EU size).
- Measure at the end of the day, when fingers are largest. Between two sizes, choose the larger.
Still unsure? Every ring includes one complimentary resizing within its first year, or visit the atelier for a fitting.
| US | UK | Diameter | EU / mm |
|---|---|---|---|
| 4 | H½ | 14.9 mm | 47 |
| 4.5 | I½ | 15.3 mm | 48 |
| 5 | J½ | 15.7 mm | 49 |
| 5.5 | K½ | 16.1 mm | 51 |
| 6 | L½ | 16.5 mm | 52 |
| 6.5 | M½ | 16.9 mm | 53 |
| 7 | N½ | 17.3 mm | 54 |
| 7.5 | O½ | 17.7 mm | 56 |
| 8 | P½ | 18.1 mm | 57 |
| 8.5 | Q½ | 18.5 mm | 58 |
| 9 | R½ | 19.0 mm | 60 |
| 9.5 | S½ | 19.4 mm | 61 |
| 10 | T½ | 19.8 mm | 62 |