If you have a heart-shaped diamond, and you want to find out its carat weight just by using its measurements, you can use either a formula or a size-to-weight conversion table. Let’s see how each of these methods works in practice.
Estimating the Carat Weight of a Heart-Shaped Diamond with a Formula
The approximate weight of a heart-shaped diamond can be estimated by plugging the stone’s length, width, and depth into the following formula:
Carat Weight = Length x Width x Depth x 0.006
The length of a heart-cut diamond is defined as the distance from its pointed end to the farthest point on the stone’s cleft side.
The width of such a stone should be measured at its widest part.
Depth is simply the distance from the lowest point at the bottom of the stone to its topmost facet.
Example: Suppose you have a heart-shaped diamond whose length is 5 mm, and it width is equal to its length.
If the depth of the stone is 3 mm, then its approximate carat weight can be estimated as follows:
5 mm x 5 mm x 3 mm x 0.006 = 0.45 ct
When interpreting this result, you shouldn’t view it as precise. In fact, it is recommended that you allow for an estimation error of about +/- 10-15%. So in this case, the actual weight of the diamond should be expected to be in the 0.40-0.50 ct range.
Millimeter-to-Carat Conversion Table for Heart-Shaped Diamonds
A quick way to figure out where your diamond stands with respect to carats is to use a conversion table that tells you what weight approximately corresponds to certain measurements.
This method is less precise than using a formula but works ok if you just want to get an idea of whether your stone is closer to 0.5 carats or 1 carat, for example.
In the table below, you have length and width measurements on the left (the table assumes that the length and width of a heart-shaped stone are equal, which they often are, even if approximately).
Measure the length and width of your diamond, and in the table below, find the measurements that are closest to your results.
On the right is the approximate guessed value of your stone’s weight:
4.2 x 4.2 mm – 0.25 ct
5.4 x 5.4 mm – 0.50 ct
6.0 x 6.0 mm – 0.75 ct
6.7 x 6.7 mm – 1.00 ct
7.1 x 7.1 mm – 1.25 ct
7.6 x 7.6 mm – 1.50 ct
8.3 x 8.3 mm – 2.00 ct
8.5 x 8.5 mm – 2.50 ct
9.5 x 9.5 mm – 3.00 ct
10.0 x 10.0 mm – 4.00 ct
11.0 x 11.0 mm – 5.00 ct
Use the above table only to make a rough estimate. If you want results that are a little more precise, then use the formula.