Carats to Milligrams
Convert carats to milligrams instantly — one carat is 200 milligrams.
| Carats | Milligrams |
|---|---|
| 1 ct | 200 mg |
| 2 ct | 400 mg |
| 3 ct | 600 mg |
| 5 ct | 1000 mg |
| 10 ct | 2000 mg |
| 25 ct | 5000 mg |
| 50 ct | 10000 mg |
| 100 ct | 20000 mg |
How to use
- Enter a value in the Carats field.
- The Milligrams figure appears immediately — no button to press.
- Typing in the Milligrams field converts back to Carats the same way.
- Use the reference table for the values that come up most often.
Carats to Milligrams formula
The factor from carats to milligrams is 200.
mg = ct × 200
Put another way, one carat is exactly 200 milligrams.
Why this factor: the carat and the milligram are both defined against the kilogram, so dividing one definition by the other gives 200 directly. Both definitions are set out in full below.
To go the other way, divide by 200 — or use the Milligrams to Carats converter, which is the same calculation reversed.
Worked example
Given 2 ct, multiplying by 200 yields 400 mg.
2 ct × 200 = 400 mg
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 milligram?
A milligram is one thousandth of a gram — the standard unit for drug doses and micronutrients.
Definition: Exactly 1×10⁻⁶ kilogram by SI prefix definition.
Where it is used: Medication dosages, vitamin and mineral content, and analytical chemistry.
Carats vs Milligrams
The carat is a specialized unit while the milligram 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 milligrams are in a carat?
One carat equals 200 milligrams.
What is the formula to convert carats to milligrams?
Multiply the number of carats by 200. To reverse it, divide by 200 instead.
How do I convert milligrams back to carats?
Divide by 200, which is the same as multiplying by 0.005.
How many milligrams are in 10 carats?
10 ct works out to 2000 mg.
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.