Carat is a unit of weight most commonly applied to diamonds. One carat equals 0.2 grams or 200 milligrams and is also known as 100 ‘points’.
Carat is abbreviated as ‘ct’ or ‘cts’ and when referring to multiple diamonds as ‘ctw’ for ‘carat total weight’. For example, a three-stone ring with a 0.50ct. center and two 0.25ct. side diamonds will have 1.00ctw (0.25+0.50+0.25=1.00).
Carats, points and fractions are used interchangeably:
- 0.33 carat = 33 points = 1/3 carat = 66 milligrams = 0.066 grams
- 0.50 carat = 50 points = 1/2 carat = 100 grams = 0.10 grams
Carat Weight Pricing
Carat weight has the largest impact on the price of the diamond. Larger carat weights are exponentially more difficult to grow, so are more rare and are priced accordingly. For example, one 1.0 carat diamond costs more than the sum of two 0.50 carat diamonds.
All diamonds are priced according to their carat weight, but they are grouped into price categories. By selecting a diamond just ‘underweight’, it is possible to save money. For example, a 0.49 carat diamond may be 6-8% less than a 0.50 carat. Though it is only 1 point less weight, it is in the next lower price category.
Carat versus Dimension and Shape
Carat weight is not the same as the size or measurements of a diamond. While each stone has specific dimensions, they vary from stone to stone depending on the cut proportions and shape.
Different shapes have carat weight distributed differently throughout the stone. A round brilliant has a good overall balance of weight distribution, while a princess cut holds more weight in the depth of the diamond.
While carat weight does not translate exactly to measurements, it is possible to obtain average dimensions based on production and grading weights. The following table shows general dimensions, in millimeters, for various carat sizes:
| 0.25 | 0.33 | 0.50 | 0.75 | 1.00 | 1.25 | 1.50 | 2.00 | |
| Round | 4.0 | 4.5 | 5.2 | 6.0 | 6.5 | 7.0 | 7.4 | 8.2 |
| Princess | 3.4 | 3.75 | 4.35 | 5.0 | 5.5 | 5.9 | 6.5 | 7.5 |
| Radiant | 4.0 | 4.1 | 4.6 | 5.2 | 5.8 | 6.2 | 7.0 | 7.5 |
| Asscher | 3.4 | 4.0 | 4.3 | 5.25 | 5.65 | 6.2 | 6.5 | 7.5 |
| Cushion | 3.4 | 4.1 | 4.7 | 5.5 | 6.0 | 6.25 | 6.5 | 7.5 |
| Emerald | 4.0×3.5 | 4.4×3.7 | 5.5×4.0 | 5.8×4.8 | 6.5×5.2 | 7.0×5.5 | 8.0×6.0 | 8.5×6.5 |
| Oval | 5.0×3.0 | 5.5×3.8 | 6.3×4.5 | 7.4×5.25 | 7.7×5.5 | 8.0×5.7 | 8.3×6.0 | 8.5×6.5 |
All measurements are examples. Specific diamonds will vary.
Choosing a Carat Weight
As with shape and color, choosing carat weight is primarily a personal preference. While there isn’t a right or wrong carat weight, here are some general guidelines to help determine what weight may be appropriate for you and your situation:
- The national average is between 0.30 and 0.50 carats, with major metropolitan areas averaging between 0.50 and 1.50 carats. The average carat weight throughout Europe is 0.30 carats.
- The national average price for an engagement ring is between $2,500 and $4,000.
- An overused claim is spending two months salary. Though this may serve as a starting point, personal preference should overrule any generic income guidelines. It is also a good rule to not go into debt when buying a ring.
- The activity level of the wearer should be considered. For example, someone who uses workout equipment regularly may prefer a smaller stone or a mounting that will better protect it.
- The profession of the wearer should be considered. A surgeon may not be able to wear a large ring, while an office worker wouldn’t have such a constraint. Furthermore, a social worker may prefer a more modest carat weight or setting while a socialite may want a larger stone or a more elaborate ring.
- If the recipient frequently wears jewelry, the size of jewelry can serve as a guide. If they do not wear jewelry, a smaller size may be more appropriate.
- A diamond will look larger on smaller fingers.
- The design of the engagement ring can justify different carat weights, such as a three-stone versus a solitaire setting.
- Availability of specific colors, shapes and qualities. We may not have your ideal stone in-stock when you want it.
- While it may be easy to get caught up in the numbers (e.g. even carat weights 1.00, or 1-2% of a cut proportion), once the diamond is mounted and worn on a daily basis, the specific measurements are not as important as it being pretty, unique and meaningful for the recipient.
If you have any questions or would like some help determining what carat weight or setting may be best for your situation, please don’t hesitate to contact us.
Carat Weight Availability
Currently, we can offer fancy yellow diamonds up to two carats. Blues are available up to 1.25ct., sometimes larger, and whites are available up to 5.0ct. These sizes are more of an upper limit, rather than an average.