---
title: "Carat weight: meaning in gemology"
description: "Carat weight is the weight of a gemstone. One carat is 200 milligrams, a fifth of a gram, and it has 100 points."
url: https://digitalgemology.com/learn/glossary/carat-weight
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

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[Glossary](https://digitalgemology.com/learn/glossary) · Four Cs

# Carat weight

Also called carat, ct, points, pointer

Carat weight is the weight of a gemstone. One carat is 200 milligrams, a fifth of a gram, and it has 100 points.

## In more detail

Carat is weight, not size. Width grows only with the cube root of weight. So a 2 ct diamond is only about 26% wider than a 1 ct. In our simulator, a 1.00 ct T73 diamond is 6.48 mm across and a 2.00 ct is 8.16 mm.

## On a grading report

In the grades block, to the hundredth of a carat. GIA's balance reads to five decimal places and IGI's to four; both report two.

## Related terms

- [Magic sizes](https://digitalgemology.com/learn/glossary/magic-sizes): Magic sizes are round-number weights, such as half a carat or one carat. They sell for more because of demand, not looks.
- [Measurements](https://digitalgemology.com/learn/glossary/measurements): Measurements is the report line that gives a stone's size in millimeters. A round reads minimum – maximum diameter × depth, and a fancy shape length × width × depth.
- [Four Cs](https://digitalgemology.com/learn/glossary/four-cs): The four Cs are color, clarity, cut and carat weight: four scales that describe the quality of a diamond. GIA made them into a grading system in the 1950s.
- [Weight ratio](https://digitalgemology.com/learn/glossary/weight-ratio): Weight ratio is the part of GIA's cut grade that compares a diamond's weight with its diameter. A stone can carry too much or too little weight for its width.
- [Specific gravity](https://digitalgemology.com/learn/glossary/specific-gravity): Specific gravity compares a stone's weight with the weight of the same volume of water. It decides how much a stone of a given size weighs.

## Learn more

- [Carat weight vs size: why a 2 ct diamond isn't twice as big](https://digitalgemology.com/learn/four-cs/carat-weight-vs-size)
- [The ID section of a diamond report: number, shape and measurements](https://digitalgemology.com/learn/grading-reports/diamond-report-identity-section)

[All 328 terms](https://digitalgemology.com/learn/glossary)