Carats to grams

1 carat = 0.2 grams

Type a value in carats (ct) to get grams (g) straight away. A carat is smaller than a gram, so the number goes down. Both units belong to weight, measured here against the kilogram.

FromTo0.2

1 ct = 0.2 g

Formula

g = ct × 0.2

One carat is 0.2 grams, so multiply by that factor. You can also divide by 5, the number of carats in one gram. Here ct is the value in carats and g is the result in grams.

Worked example: 5 carats × 0.2 = 1 gram.

Carats to grams table

carats (ct)	grams (g)
1 ct	0.2 g
2 ct	0.4 g
3 ct	0.6 g
4 ct	0.8 g
5 ct	1 g
6 ct	1.2 g
7 ct	1.4 g
8 ct	1.6 g
9 ct	1.8 g
10 ct	2 g
15 ct	3 g
20 ct	4 g
25 ct	5 g
30 ct	6 g
40 ct	8 g
50 ct	10 g
60 ct	12 g
75 ct	15 g
100 ct	20 g

Everyday carats in grams

What it is	ct	g
a quarter-carat stone	0.25 ct	0.05 g
a half-carat stone	0.5 ct	0.1 g
a one-carat diamond	1 ct	0.2 g
a two-carat diamond	2 ct	0.4 g
a large gemstone	5 ct	1 g

Quick estimate in your head

Multiply by about 0.2. For 5 ct that gives 1 g against an exact 1 g, an error under 0.1%.

Watch out for

Carat (ct) is gemstone weight. Karat (K) is gold purity, where 24K is pure gold. They are unrelated.

About the units

Carat (ct). Exactly 200 mg. Used for gemstones (not to be confused with karat, the gold purity scale).

Gram (g). One thousandth of a kilogram. Used for food, post and jewellery.

Going the other way, 1 gram is 5 carats.

Questions

How many grams are in 1 carat?

1 carat is 0.2 grams, and 1 gram is 5 carats.

How do I convert carats to grams?

Use g = ct × 0.2. For example, 5 carats × 0.2 = 1 gram.

Is the carat to gram factor exact?

The factor comes from the unit definitions. Results here are rounded to 6 significant digits for display.

How much is a large gemstone in grams?

5 ct is 1 g.

Source for the conversion factor: NIST SP 811, Appendix B (conversion factors).

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