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Carat to Grams

Use this free carat to grams converter to change gemstone weight between carats, grams, kilograms, grains, ounces, and troy ounces. Enter a value, pick the unit you have and the unit you want, and the result updates instantly — in both directions, with all six units available on either side.

How it works

The carat is the standard unit for weighing gemstones, and it has one clean definition: one carat is exactly 0.2 grams. That means five carats make one gram, and converting in either direction is a single multiplication — carats times 0.2 gives grams, and grams times 5 gives carats. The name comes from the carob seed, which traders once used as a counterweight because the seeds were thought to be nearly identical in weight; the modern carat is far more exact than any seed.

Gemstones are also weighed in points: one point is one hundredth of a carat, or 2 milligrams. A 0.50-carat stone is therefore a fifty-point stone, and a 1.25-carat stone is one hundred and twenty-five points. Jewelers quote small stones in points and larger ones in carats, but both are the same unit underneath.

The other units in this converter cover the rest of the weighing world. A kilogram is 1,000 grams, or 5,000 carats. A grain — the oldest unit here, still used for pearls and small gemstones — is exactly 0.06479891 grams, so one carat is about 3.0865 grains. The everyday ounce is 28.3495 grams, or about 141.75 carats, while the troy ounce used for precious metals and gemstones is heavier at 31.1035 grams, or about 155.52 carats. Mixing up the two ounces is an easy mistake worth avoiding: a troy ounce is roughly 10 percent heavier than an everyday ounce.

Weight is only part of a gemstone's story. Two diamonds of the same carat weight can look very different, because cut, shape, and density change how large a stone appears. A well-cut round stone spreads its weight across the top, while a deep-cut stone hides weight in its base and looks smaller. Price also rises faster than weight: a 2-carat stone of the same quality usually costs far more than twice a 1-carat stone, because large rough crystals are rarer. The converter tells you the weight exactly; value depends on the stone itself.

Worked example

An engagement ring has a 1.5-carat center diamond. How much does the stone weigh in grams, and how many grains is that?

Step 1: Convert to grams — 1.5 × 0.2 = 0.3 g.
Step 2: Convert to grains — 0.3 ÷ 0.06479891 = 4.6297 grains.
Step 3: Check the other way — 0.3 × 5 = 1.5 carats, so the round trip closes.

Try it in the converter: enter 1.5, choose carats on the left and grams on the right, and you will see 0.3 g, with grains and the other units listed underneath.

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