By Nick Coutu
Diamond Carat Chart: Weight, Size and Your Ring
A diamond needs to make sense in the ring you want to create. Carat weight is part of that decision. So are its shape, its proportions and the way it looks to the person who will wear it.
Start with the number, then look at the stone.
Diamond carat weight chart
One carat equals 0.20 grams and is divided into 100 points. This is a weight chart, not a scale drawing of diamond size.
| Carat weight | Points | Weight in grams |
|---|---|---|
| 0.25 ct | 25 | 0.05 g |
| 0.50 ct | 50 | 0.10 g |
| 0.75 ct | 75 | 0.15 g |
| 1.00 ct | 100 | 0.20 g |
| 1.50 ct | 150 | 0.30 g |
| 2.00 ct | 200 | 0.40 g |
| 3.00 ct | 300 | 0.60 g |
Source: GIA — Carat Weight. Gram and point values are arithmetic conversions.
How large will it look?
Carat weight alone cannot give you an exact diameter or length. Read the measurements on the individual diamond's grading report, then consider them alongside the design.
When comparing stones, ask to see their dimensions together. A photograph enlarged to fill a screen is useful for examining detail, but it cannot tell you how large the diamond will look on a hand.
A larger outline is not the whole story
Measurements and proportions deserve careful attention at every carat weight. Someone comparing diamonds for the first time may favour the stone with the largest diameter, overlooking the proportions that help it handle light well. A shallower diamond can spread its weight across a wider outline, but that extra apparent size may come at the expense of brightness and fire. A deeper stone can carry weight that adds little to the size you see from above.
You should not have to abandon good proportions to reach a particular carat weight. For round brilliants, several combinations of proportions can produce excellent results; there is not one universal set of ideal measurements for every diamond shape. Read the grading report and assess the stone itself rather than treating the largest millimetre measurement as the best choice.
Our cut guide explores this in more detail. Here, the useful starting point is to compare carat weight, measurements, proportions and appearance together.
Source: GIA — Diamond Cut: The Wow Factor.
Put the diamond beside the design
If you are choosing for yourself, bring examples of the proportions you enjoy. If you are choosing for your partner, start with what you know about their taste. Couples choosing together can use the same approach.
Think about the whole ring: the outline of the centre stone, the width of the band and the details that make the design personal. Bring those preferences into the conversation before settling on a carat target.
Compare the complete proposal
Ask what each quoted price includes. A diamond price and a complete-ring price are different things; the setting, specifications and applicable taxes need to be clear.
For a custom commission, share your budget and the qualities you care about. We can discuss the stone and the design together, with the final quote confirmed for your chosen specifications.
Choose your next step
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