Carats to Grams
Type a value in either box to convert between carats and grams. The factor is 0.2.
| Carats | Grams |
|---|---|
| 1 ct | 0.2 g |
| 2 ct | 0.4 g |
| 3 ct | 0.6 g |
| 5 ct | 1 g |
| 10 ct | 2 g |
| 25 ct | 5 g |
| 50 ct | 10 g |
| 100 ct | 20 g |
How to use
- Enter a value in the Carats field.
- The Grams figure appears immediately — no button to press.
- Typing in the Grams field converts back to Carats the same way.
- Use the reference table for the values that come up most often.
Carats to Grams formula
The factor from carats to grams is 0.2.
g = ct × 0.2
Put another way, one carat is exactly 1/5 of a gram.
Why this factor: the carat and the gram are both defined against the kilogram, so dividing one definition by the other gives 0.2 directly. Both definitions are set out in full below.
To go the other way, divide by 0.2 — or use the Grams to Carats converter, which is the same calculation reversed.
Worked example
Given 150 ct, multiplying by 0.2 yields 30 g.
150 ct × 0.2 = 30 g
The converter above does this for any value you type, in either direction.
What is a carat?
A metric carat is the standard mass unit for gemstones.
Definition: Exactly 200 milligrams — that is, 0.2 gram — standardized internationally in 1907.
Where it is used: Diamond and gemstone weight throughout the jewellery trade.
Worth knowing: Do not confuse the carat (gemstone mass) with the karat (gold purity out of 24). A 1-carat diamond and 24-karat gold measure entirely different things.
What is a gram?
A gram is one thousandth of a kilogram, the everyday unit for food and small-object mass.
Definition: Exactly 0.001 kilogram by SI prefix definition.
Where it is used: Nutrition labels, recipes, postal rates, and laboratory weighing.
Carats vs Grams
The carat is a specialized unit while the gram is a metric unit. That is why the factor between them is not a round number: the two systems were defined independently and only later tied together by exact agreement.
Frequently asked questions
How many grams are in a carat?
One carat equals 0.2 grams.
What is the formula to convert carats to grams?
Multiply the number of carats by 0.2. To reverse it, divide by 0.2 instead.
How do I convert grams back to carats?
Divide by 0.2, which is the same as multiplying by 5.
How many grams are in 10 carats?
10 ct works out to 2 g.
Is there anything to watch out for with carats?
Do not confuse the carat (gemstone mass) with the karat (gold purity out of 24). A 1-carat diamond and 24-karat gold measure entirely different things.
How is the carat defined?
Exactly 200 milligrams — that is, 0.2 gram — standardized internationally in 1907.