Gemstone Weight Guide

Carat to Ratti Converter

Gem certificates state weight in carats, while astrological recommendations are usually given in rattis. Convert between carat, ratti, gram and milligram instantly — type in any field and the rest follow.

Weight converter

Enter a weight in any one field — the other three update as you type.

Carat1 ct = 200 mg

Ratti1 rt = 0.91 ct

Gram1 g = 5 ct

Milligram1 ct = 200 mg

Start typing in any field — carat, ratti, gram or milligram.

Uses the standard (pakki) ratti of the Indian gem trade: 1 ratti = 0.91 carat = 182 mg, with 1 carat = 200 mg. The traditional kachi ratti (≈121.5 mg) is a different, older measure — confirm which convention your astrologer uses before buying by weight.

Quick reference

Ratti	Carat	Gram	Milligram
0.5	0.46	0.091	91
1	0.91	0.182	182
2	1.82	0.364	364
3	2.73	0.546	546
4	3.64	0.728	728
5	4.55	0.910	910
6	5.46	1.092	1092
7	6.37	1.274	1274
8	7.28	1.456	1456
9	8.19	1.638	1638
10	9.10	1.820	1820
11	10.01	2.002	2002
12	10.92	2.184	2184

Standard gem-trade convention: 1 ratti = 0.91 carat = 0.182 g = 182 mg, and 1 carat = 0.2 g = 200 mg.

How to use the converter

Type a weight into any one field — carat, ratti, gram or milligram.
The other three fields calculate instantly as you type; no button to press.
Compare the ratti figure against your astrological recommendation, or the carat figure against a laboratory certificate.
Press Reset to clear all four fields and start a fresh conversion.

Why accurate conversion matters

Gemstones are priced per carat, and for fine stones the per-carat rate itself rises with size — so a small weight misunderstanding compounds into a large price difference. Converting correctly lets you compare quotes on equal terms.

Astrological prescriptions add a second reason: a recommendation of “at least 5 ratti” means at least 4.55 carats. Mistake ratti for carat and you may buy a stone nearly 10% lighter than intended — or pay for weight you did not need.

Finally, the two ratti conventions differ by almost 50%. Every conversion on this page uses the standard pakki ratti (0.91 ct) and says so — so the number you see is the number the trade means.

Understanding the conversions

Every figure below follows one convention — 1 carat = 200 mg, 1 ratti = 0.91 carat — the same constants the converter uses.

Carat vs Ratti — two systems, one stone

The carat is the international unit of gemstone weight: exactly 200 milligrams, standardised worldwide and used on every laboratory certificate. The ratti is the traditional Indian unit, and it is the measure most astrologers use when they recommend a gemstone — "a 5-ratti Yellow Sapphire", for instance.

The two coexist on almost every Indian gemstone purchase: the certificate states carats, the recommendation states rattis. This page bridges them with the standard (pakki) ratti of the gem trade — 0.91 carat, or 182 milligrams. Note that the older kachi ratti (about 121.5 mg, the weight of a Gunja seed) is a different measure; always confirm which one a recommendation refers to.

Carat to Gram

One carat equals exactly 0.2 gram, so dividing a carat weight by 5 gives grams. A 10-carat gemstone weighs 2 grams; a 2.5-carat stone weighs 0.5 gram.

Because the definition is exact, this conversion carries no rounding at all — it is the same in every laboratory and every market in the world.

Gram to Carat

One gram equals exactly 5 carats — multiply grams by 5. A stone weighing 1.5 grams is 7.5 carats; a 0.36-gram stone is 1.8 carats.

Jewellers often weigh in grams on a balance and quote in carats: the factor of 5 moves cleanly between the two.

Carat to Ratti

Divide carats by 0.91 — equivalently, multiply by about 1.0989. A 1-carat gemstone is roughly 1.1 ratti; a 5-carat stone is about 5.49 ratti; a 7.25-carat stone is about 7.97 ratti.

This matters most when checking a purchase against an astrological prescription: a "5-ratti" recommendation corresponds to about 4.55 carats, so a 5-carat certificate weight already exceeds it.

Ratti to Carat

Multiply rattis by 0.91. A 6-ratti recommendation is 5.46 carats; 9 ratti is 8.19 carats; 2.5 ratti is about 2.28 carats.

When shopping from a certificate, convert the prescribed ratti into carats first — then you can compare directly against the certified weight, which is always stated in carats.

Frequently asked questions

How many ratti is 1 carat?

About 1.0989 ratti, using the standard gem-trade (pakki) ratti of 0.91 carat. In practice, 1 carat is usually rounded to 1.1 ratti.

How many carats is 1 ratti?

0.91 carat, which is 182 milligrams or 0.182 gram. This is the pakki ratti convention followed by the Indian gemstone trade and by this converter.

What is the difference between pakki and kachi ratti?

The pakki (standard) ratti used by the modern gem trade equals 0.91 carat (182 mg). The kachi ratti is the older seed-based measure of about 121.5 mg. A "5-ratti" stone differs by more than 300 mg between the two conventions, so always confirm which one is meant.

Why does my certificate show carats when my astrologer prescribed ratti?

Laboratories certify in the international carat; astrological tradition works in ratti. Convert the prescription to carats (ratti × 0.91) and compare it with the certified weight — the converter above does this instantly.

Is a carat the same as a karat?

No. Carat (ct) measures gemstone weight — 200 mg. Karat (kt) measures gold purity — 24 karat is pure gold. The words sound alike but are unrelated measures.

Does carat weight decide a gemstone’s price by itself?

No — price depends on variety, colour, clarity, cut, origin and treatment as well as weight. Weight matters because per-carat rates climb steeply for larger fine stones, which is why an accurate conversion is worth doing before comparing quotes.