Diamonds · 5 minute read · Updated October 2026
The diamond 4Cs, explained
Cut, color, clarity and carat weight in plain words, and what each one does to the price.
Book a free consultation
The 4Cs are cut, color, clarity and carat weight. The Gemological Institute of America (GIA) set them out, and grading reports worldwide use them.
Cut
Cut is how well the facets are angled and proportioned. It decides how much light comes back out of the stone, so two diamonds of the same shape and weight can look very different: one bright across the whole face, the other dull in the middle.
Cut is not shape. Shape is the outline seen from above (round, oval, pear); cut is the quality of the faceting inside that outline. Our diamond shapes guide covers the outlines.
Grading reports give a cut grade only for round brilliant diamonds, from Excellent to Poor. For other shapes the report gives polish and symmetry grades and the measurements, and the best test is to see the stone.
A good cut shows even brightness from edge to edge. On a fancy shape, the bow tie (the dark band across the middle) should be faint rather than black.
What it does to the price: cut has the smallest price steps of the four and the biggest effect on looks. Buy the best cut you can and save on the other three.
Color
Color grades run from D down the alphabet to Z as a faint yellow or brown tint becomes visible.
- D, E and F: colorless.
- G, H, I and J: near colorless. They look white to the eye once the diamond is set.
- K to Z: a tint that grows further down the scale.
Color is graded with the stone upside down against a white background, which is where the tint shows. Face up, in a ring, a G and a D are very hard to tell apart. Yellow and rose gold settings warm the stone and hide a tint further; white gold and platinum show it a little more.
Fancy colored diamonds, such as yellow and pink, are graded on a separate scale where more color is better.
What it does to the price: each letter is a step in price. Moving from D to G can save a good share of the cost for a difference you will not see on the hand.
Clarity
Clarity measures the small natural marks inside and on the surface of a diamond, by how easily they can be seen at 10x magnification. The grades, from the top:
- FL and IF: Flawless and Internally Flawless.
- VVS1 and VVS2: very, very slightly included.
- VS1 and VS2: very slightly included.
- SI1 and SI2: slightly included.
- I1, I2 and I3: included.
The grade that matters on a hand is eye-clean: no mark visible without a loupe. Most VS stones are eye-clean, and many SI1 stones are too, depending on where the inclusion sits. A mark under a prong disappears, and a mark in the middle of the table does not.
Two SI1 diamonds can look very different, which is why we show the stone, not the paper.
What it does to the price: large steps between grades. VS2 and a carefully chosen SI1 are where most engagement diamonds land, and where the money goes furthest.
Carat weight
Carat is a weight, not a size. One carat is 0.2 grams, divided into 100 points, so a 0.50 carat diamond is 50 points. A one-carat round diamond is about 6.5 mm across.
Weight and size do not move together across shapes. An oval, pear or marquise of the same weight spreads its weight over a larger face, so it looks bigger than a round of the same carat. A deep-cut stone hides weight underneath where it does not show.
Total carat weight (ct tw) adds up every diamond in the piece, side stones included, so a ring listed at 1.00 ct tw can have a much smaller center diamond. On our product pages the center stone and the total weight are listed separately where the catalog carries them.
What it does to the price: price per carat jumps at the round numbers, 0.50, 1.00, 1.50 and 2.00 carats, because demand does. A 0.90 carat diamond looks almost the same as a 1.00 carat and costs noticeably less.
Buy the diamond you can see: cut first, then an eye-clean stone, then near colorless, then the weight that fits.
How to choose in a budget
- Shape first. It changes the look of the ring most, and the same weight is priced differently by shape.
- Cut: spend here. Excellent or Very Good on a round; even brightness and a faint bow tie on a fancy shape.
- Color: save here. G to H in white metal, H to J in yellow or rose gold.
- Clarity: save here. VS2 or an eye-clean SI1, checked in person.
- Carat: spend what is left, and stop just under a round number if it keeps the diamond you want.
Lab-grown diamonds are graded on the same scales and cost less than natural diamonds of the same grade, so the same steps work. Lab-grown diamonds vs natural diamonds covers the differences and how trade-ins work for each.
Reading a grading report
A grading report from GIA or another laboratory states the shape, the measurements, the carat weight, the color and clarity grades, the cut grade on a round, the polish, symmetry and fluorescence, and a plotted diagram of the inclusions.
The report number is often inscribed on the girdle of the stone, which ties the paper to the diamond.
A report describes a diamond; it does not judge its beauty, and two diamonds with identical reports can look different. Use the report to narrow the choice and your eyes to make it.
See them side by side
Every engagement ring in our case shows its price online.
In the store we put diamonds of different grades next to each other under the same light, so you can see which steps show and which do not. We will also go through a report you have been sent.
If you would rather start with the setting and choose the diamond with us, the custom design page explains how.
Frequently asked questions
Which of the 4Cs matters most?
Cut. It decides how much light comes back out of the diamond, so a well-cut stone of a modest color and clarity grade looks brighter than a poorly cut stone with better grades.
What color grade should an engagement diamond be?
G to J, called near colorless, looks white to the eye once the diamond is set, especially in yellow or rose gold. D to F is colorless and costs more for a difference that is hard to see in a ring.
What does eye-clean mean?
A diamond whose inclusions cannot be seen without magnification. Most VS stones and many SI1 stones are eye-clean, and they cost less than higher clarity grades that look the same on the hand.
Is a one-carat diamond big?
A one-carat round diamond is about 6.5 mm across. Carat is weight, not size, so a well-cut oval or pear of the same weight looks larger, and a 0.90 carat stone looks almost the same as a 1.00 carat stone for less money.
Are lab-grown diamonds graded on the same 4Cs?
Yes. Lab-grown diamonds are real diamonds and are graded on the same cut, color, clarity and carat scales. The report states that the stone is laboratory-grown.
From the case
