Milligrams to Carats
An instant milligrams-to-carats converter, with the formula and a reference table below.
| Milligrams | Carats |
|---|---|
| 1 mg | 0.005 ct |
| 2 mg | 0.01 ct |
| 3 mg | 0.015 ct |
| 5 mg | 0.025 ct |
| 10 mg | 0.05 ct |
| 25 mg | 0.125 ct |
| 50 mg | 0.25 ct |
| 100 mg | 0.5 ct |
How to use
- Enter a value in the Milligrams field.
- The Carats figure appears immediately — no button to press.
- Typing in the Carats field converts back to Milligrams the same way.
- Use the reference table for the values that come up most often.
Milligrams to Carats formula
To convert milligrams to carats, multiply by 0.005.
ct = mg × 0.005
Put another way, one milligram is exactly 1/200 of a carat.
Why this factor: the milligram and the carat are both defined against the kilogram, so dividing one definition by the other gives 0.005 directly. Both definitions are set out in full below.
To go the other way, divide by 0.005 — or use the Carats to Milligrams converter, which is the same calculation reversed.
Worked example
Start with 150 mg. Multiply by 0.005 to get 0.75 ct.
150 mg × 0.005 = 0.75 ct
The converter above does this for any value you type, in either direction.
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.
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.
Milligrams vs Carats
The milligram is a metric unit while the carat is a specialized 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 carats are in a milligram?
One milligram equals 0.005 carats.
What is the formula to convert milligrams to carats?
Multiply the number of milligrams by 0.005. To reverse it, divide by 0.005 instead.
How do I convert carats back to milligrams?
Divide by 0.005, which is the same as multiplying by 200.
How many carats are in 10 milligrams?
10 mg works out to 0.05 ct.
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 milligram defined?
Exactly 1×10⁻⁶ kilogram by SI prefix definition.