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Diamond Carat to Grams Converter

Everyday

Convert diamond and gemstone weight between carats, grams, milligrams, and points — using the exact international standard of 1 carat = 0.2 grams.

Reviewed by the thecalcu.com team · Last updated July 20, 2026

From
To
All conversionsfor 1 Carat (ct)
Carat (ct)1
Point (1/100 ct)100
Gram (g)0.2
Milligram (mg)200

What is a Carat Weight?

A Diamond Carat to Grams Converter translates gemstone weight between the carat, the standard unit used worldwide for diamonds and precious stones, and metric mass units like grams and milligrams. Unlike many historical units, the carat has an exact, internationally standardised definition: 1 carat equals precisely 0.2 grams, fixed by international agreement in 1907, so this conversion involves no approximation.

This is distinct from the general Weight Converter, which handles everyday mass units but doesn't include carat or the jewellery-trade "point" subunit, both of which carry specific meaning in the gemstone and jewellery industry that deserves a dedicated, precise tool.

Why Use a Diamond Carat to Grams Converter?

Diamond and gemstone certificates, jewellery listings, and appraisal documents describe weight in carats or points, while a jeweller's scale or shipping documentation often measures in grams or milligrams. Converting between the two, especially for small stones measured in points, requires knowing the exact carat-to-gram relationship rather than estimating.

Two concrete situations this solves: converting a diamond certificate's carat weight into grams to cross-check against a jeweller's scale reading, and converting a "50-pointer" diamond description into its exact carat and gram equivalents for a purchase comparison.

Who Should Use This Converter?

  • Diamond and jewellery buyers verifying that a stone's carat weight matches its certification or the jeweller's scale reading.
  • Gemologists and appraisers converting between carat, point, and gram measurements when documenting or certifying gemstones.
  • Jewellery designers calculating total stone weight across a piece with multiple small diamonds described in points.
  • Online jewellery shoppers cross-checking a listing's carat weight against gram-based shipping or customs documentation.
  • Students studying gemology, learning the standardised carat-to-gram relationship and the point subunit convention.

What Insights Does the Carat Weight Converter Give You?

Converting Carat to Gram (g) or Milligram (mg) gives you the exact metric mass of a diamond or gemstone, useful for cross-referencing against scale measurements or scientific documentation. Converting to Point (1/100 ct) gives you the jewellery-trade shorthand commonly used for diamonds under 1 carat, where whole numbers (like "75 points") are easier to communicate than long decimal carat values.

Because the carat-to-gram relationship is an exact, fixed standard rather than an approximation, every value this converter produces is precise, there's no rounding uncertainty to account for when using the result in a purchase, appraisal, or certification comparison.

How to use this Carat Weight calculator

  1. Select your starting unit from the From dropdown, Carat (ct), Point (1/100 ct), Gram (g), or Milligram (mg).
  2. Enter your value, such as 1.25 for a 1.25 carat diamond.
  3. Select your target unit from the To dropdown, such as Gram (g).
  4. Read the converted result, which updates instantly.
  5. Use the swap (⇅) button to convert a gram or milligram scale reading back into carats.
  6. For small stones described in points, select Point as your From unit and enter the point value directly (e.g. 50 for a 50-pointer).

Formula & Methodology

All units convert through grams as the base unit, using the internationally fixed carat definition:

Grams = Carats × 0.2  |  Carats = Grams ÷ 0.2

Worked example: Converting a 0.75 carat diamond to grams, 0.75 × 0.2 = 0.15 grams (150 milligrams). Converting that same stone to points: 0.75 carats × 100 = 75 points, matching how a jeweller would describe it as a "75-pointer."

Frequently Asked Questions

1 carat equals exactly 0.2 grams (200 milligrams), a fixed international standard adopted in 1907 and used worldwide for weighing diamonds and gemstones. This exact relationship means carat-to-gram conversion involves no rounding or approximation.
Grams = Carats × 0.2, and conversely, Carats = Grams ÷ 0.2. This converter applies that exact relationship, so a 1.5 carat diamond converts to exactly 0.3 grams.
A point is a jewellery-trade subunit equal to 1/100 of a carat, used to describe small diamonds precisely, for example, a '75-pointer' means a 0.75 carat diamond. This converter includes points as a selectable unit alongside carats, grams, and milligrams.
Select Carat (ct) as your From unit, enter the diamond's carat weight, and select Gram (g) or Milligram (mg) as your To unit. The tool applies the exact 0.2 g/carat conversion instantly.
Larger diamonds are significantly rarer in nature than small ones, so price per carat increases disproportionately with size, a 2 carat diamond typically costs far more than twice the price of a 1 carat diamond of the same quality. This converter calculates weight only; it does not estimate diamond pricing, which also depends on cut, clarity, colour, and certification.
Carat (with a C) measures gemstone and diamond weight, where 1 carat = 0.2 grams, while karat (with a K) measures gold purity out of 24 parts and has no relationship to weight at all. Use this converter for gemstone weight and the [Karat Purity Converter](/karat-purity-converter/) for gold purity, the similar spelling is a common source of confusion.
A 1 carat diamond weighs exactly 0.2 grams, while a standard paperclip weighs roughly 1 gram, meaning a 1 carat diamond is about a fifth the weight of a single paperclip, despite its significant size and value in jewellery. This illustrates how physically small a 1 carat diamond actually is.
Yes, the carat is a unit of mass (200 mg), so the same 0.2 g/carat conversion applies to all gemstones (diamonds, rubies, sapphires, emeralds, and more), regardless of the stone's density or type. What differs between gemstone types is how carat weight relates to the stone's physical size, since denser gemstones are physically smaller for the same carat weight.
Jewellery with multiple small diamonds or gemstones (such as a pavé setting) is often described by 'total carat weight' (TCW), which sums the carat weight of every stone in the piece rather than describing any single stone. This converter calculates the weight of a single carat value; for multi-stone pieces, first obtain the total carat weight from the jeweller's certification.
Select Point (1/100 ct) as your From unit, enter the point value (such as 25 for a '25-pointer'), and select Carat (ct) as your To unit, the tool divides by 100 automatically, giving 0.25 carats. Points are commonly used for diamonds under 1 carat, since whole-number points are easier to read than long decimal carat values.
Also known as
carat to gramsdiamond weight convertercarat to mgpoints to caratgemstone weight converter1 carat in grams