The 4Cs, explained
Cut, color, clarity and carat, in plain words
Every diamond is graded on the same four scales, and every listing on this site prints them. Two of the four decide what you will actually see across a table; the other two decide what you pay for things you will mostly not see.
This guide takes them in the order they matter for finished jewelry, and ends with how the four trade against each other inside a budget.
Cut
Cut is not the shape. It is how well the facets are angled, so that light entering the top of the stone comes back out of the top instead of leaking through the sides. A well-cut stone looks bright and lively; a deep or shallow one looks glassy even with a high color and clarity grade.
Cut is the one grade not to compromise on, because it is the one you notice from across a room. Our round stones are cut to the Excellent or Very Good standard; fancy shapes are graded on polish and symmetry instead.
Color
Color grades run from D (no tint) to Z (a visible yellow). The scale is finer than the eye: D, E and F look identical once set, and G through J look white in a white-gold or platinum setting. Yellow and rose gold hide a faint tint further still.
Our pieces are listed in three bands, DE, EF and GH. For everyday jewelry GH is the sensible buy; move up only for a large solitaire in white metal, where the stone sits alone against its own light.
- D to F: colorless. Priced for rarity, not for a visible difference.
- G to J: near colorless. White in any setting; the best value for most pieces.
- K and below: a warm tint that reads as cream. We do not stock these.
Clarity
Clarity counts the small marks inside and on the stone, graded under ten-times magnification. From VS up, nothing is visible to the naked eye; at SI the marks are usually invisible too, which is why an SI stone with a good cut is often the best-looking stone for the money.
Our quality bands pair color and clarity: GH SI, EF VS and DE VVS. Each band is a step in rarity, not a step in sparkle.
- FL / IF: no marks even under magnification.
- VVS1 / VVS2: marks a grader struggles to find.
- VS1 / VS2: minor marks under the loupe, never without it.
- SI1 / SI2: small marks under the loupe, invisible when the stone is set and worn.
Carat
Carat is weight, not size: one carat is a fifth of a gram. Width grows slowly with weight, so a 1.00 ct round is only about a millimeter wider than a 0.75 ct, and the price difference comes from the whole-number mark, not from what you see.
The rule below draws round stones to scale next to a US dime. Our product pages use the same rule as the carat selector, so you can pick a size by width rather than by weight.
Carat weight and width, round brilliant
Widths are typical for a well-cut round; a deep stone of the same weight looks smaller.
| Carat | Width | Compared with 1.00 ct |
|---|---|---|
| 0.25 ct | 4.1 mm | 63% of the width |
| 0.50 ct | 5.1 mm | 78% |
| 0.75 ct | 5.8 mm | 89% |
| 1.00 ct | 6.5 mm | — |
| 1.50 ct | 7.4 mm | 114% |
| 2.00 ct | 8.2 mm | 126% |
| 3.00 ct | 9.4 mm | 145% |
How the four trade against each other
Inside one budget, cut comes first. Then take the clarity down to VS or SI, which the eye cannot tell apart, and spend the difference on carat or on a better setting. Color only needs attention for a large stone in white metal.
On every product page the grades are printed as a report table with the same plain-language notes as this guide, so you can compare two pieces on facts rather than on photographs.
