How to convert carats to ratti

Units of measure and weight for diamonds: the carat

The unit of measurement is that metric carats (m.K.) and corresponds to a fifth of a gram, i.e. 2 decigrams.

1 carat = 0.2 grams.

The installed balance must be well protected from:

  • Draft (no passage)
  • Heat sources
  • Shocks (vibration-protected table)

The stone must be clean.

Pay attention to the accuracy of the scale:

  • Set to zero
  • Perform measurement when empty (check reliability)
  • To weigh


  • According to professional ethics, rounding is not carried out: a hundredth of a carat that is not reached is not given (in deviation from this rule, the third 9 after the decimal point is rounded up to the higher hundredth. Examples: 0.9990 is given as 1.00 carat, 0.9989 is reported as 0.99 carats.
  • For reasons of care, single-precision scales are given the lower hundredth (it becomes 0.99 carats and not almost 1.00 carat specified).

Estimation of the weight of a diamond according to its diameter.

This unit of weight has no relation to the carats for gold alloys.

The carat is divided into 100 points (hundredths of a m.K), i.e. a diamond of 0.25 m.K. has 25 points. The same goes for other gemstones. Example: a 1.15 m.k. sapphire weighs 1 carat and 15 points.

Note that it is not uncommon to use the abbreviation in documents and on websites ct encountered.

Various types of scales are used to determine the weight of these gemstones. Click on the following link to get to know the most common scales you come across in stores: Carat scales.

For your reference, a 0.95 carat diamond is slightly more expensive than a 0.90 carat diamond, but a 1 carat diamond is much more expensive than a 0.95 carat diamond. Likewise, the value of a diamond of 2 carats is not the same as the value of 2 diamonds that are each 1 carat. Visit our Diamond Price page to see the real value of a diamond in retail.

Weight (in carats) and diameter (in millimeters) of the diamonds

0.03 carat0.05 carat0.07 carat0.10 carat
Ø 2.00 mmØ 2.50 mmØ 2.70 mmØ 3.00 mm
0.15 carat0.20 carat0.25 carat0.33 carat
Ø 3.40 mmØ 3.80 mmØ 4.10 mmØ 4.40 mm
0.40 carat0.50 carat0.65 carat0.75 carat
Ø 4.80 mmØ 5.20 mmØ 5.60 mmØ 5.90 mm
0.85 carat1.00 carat1.25 carats1.50 carat
Ø 6.20 mmØ 6.50 mmØ 7.00 mmØ 7.40 mm
1.75 carats2.00 carat2.25 carats2.50 carats
Ø 7.80 mmØ 8.20 mmØ 8.60 mmØ 9.00 mm

Weight of a gem according to the dimensions and shape of the cut

To get a realistic estimate of the weight (in carats) for a gemstone, it is sufficient to use the simulator below according to the following instructions:

  • From the drop-down list, select the gemstone whose weight you want to know.
  • Select the cut from the drop-down list.
  • Enter the length (in millimeters) or the diameter (if your stone is round).
  • Enter the width (in millimeters) or again the diameter (if your stone is round).
  • Enter the thickness of the stone (in millimeters).
  • Click the button To calculate.
There must always be 2 digits after the comma. As a decimal point
please use the point. Example: 10.34 or 5.00

We would like to point out that there can be significant differences in weight between the weight estimated by our simulator and the actual weight of the gemstone. This is especially true for colored stones or cuts that are not standardized.

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