Convert carats to stones

1 ct=3.1495e-5st

Use the converter below to change any carats value into stones instantly — with formula, conversion table, and real-world examples.

You have

Equals

3.1495e-5

Conversion formula

Forward

stones = carats × 3.1495e-5

Reverse

carats = stones × 31,751.47

Example: 10 ct × 3.1495e-5 = 0.0003149 st.

About both units

From

Carat

The metric carat equals 200 milligrams exactly. It is the standard unit for gemstone weight — diamonds, rubies, sapphires and emeralds are sold by the carat. Do not confuse with the purity carat (karat) used for gold (24K = pure gold).

Real-world: A 1-carat diamond weighs 200 mg and is typically 6.5 mm across. The Hope Diamond is 45.52 carats (9.1 g).

Read full carat reference →

Stone

The stone equals 14 pounds or 6.35 kilograms. It is used almost exclusively in the UK and Ireland to express human body weight. A 70 kg person is described as "11 stone" in British English. The stone is not used in trade, science or any other context.

Real-world: A 70 kg adult is about 11 stone. A British NHS weight chart marks stones alongside kg. A heavyweight boxer over 14 stone is typical.

Read full stone reference →

Carat to Stone conversion table

Common carats to stones values for quick reference.

Carat (ct)	Stone (st)
1 ct	3.1495e-5 st
5 ct	0.0001575 st
10 ct	0.0003149 st
25 ct	0.0007874 st
50 ct	0.001575 st
100 ct	0.003149 st
250 ct	0.007874 st
500 ct	0.01575 st
1,000 ct	0.03149 st
5,000 ct	0.1575 st

Tips & common mistakes

Quick tips

1 carat = 200 mg = 0.2 g exactly since 1907.
Carat (gem weight) and karat (gold purity, 24 K = pure) are different words with different meanings.
A carat is divided into 100 points; a 0.25 ct diamond is called a "25-pointer".

Avoid these

Confusing carat (mass) with karat (gold purity).
Assuming a 2-carat diamond is twice the physical size of a 1-carat — volume scales with cube root of mass.
Using "karat" on gemstone certificates — international standard is "carat" spelled with a C.

Frequently asked questions

How many stones in a carat?

One carat equals 3.1495e-5 stones.

How do I convert carats to stones?

Multiply the carat value by 3.1495e-5 to get the equivalent in stones.

What is 100 carats in stones?

100 carats equals 0.003149 stones.

Is a carat bigger than a stone?

No. 1 carat equals 3.1495e-5 stones, so one carat is smaller.

How to convert carats to stones without a calculator?

Multiply by 0 for a quick estimate; use a calculator for precise results.

Related weight conversions

📊 See full comparison matrix →

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