Carat and ratti are both units used to measure gemstone weight, but they belong to two different systems: carat (1 carat = 200 mg) is the international standard accepted worldwide and used on every gemological certificate, while ratti (1 ratti ≈ 0.91 carats ≈ 182 mg) is a traditional Indian unit still widely used for astrological gemstone recommendations. Neither is "more correct" than the other — they simply serve different purposes, and knowing when to use which one is what actually matters when you're buying.
What Is a Carat?
Carat is the globally standardized unit for weighing gemstones, diamonds, and pearls. One carat equals exactly 200 milligrams, and it's further divided into 100 "points" for precision — so a 0.75-carat stone is often called "75 points." The term traces back to the carob tree, whose seeds were historically used as a natural, fairly consistent reference weight by ancient gem traders.
Every gemological laboratory in the world — whether in India, the US, or anywhere else — issues certificates using carat, making it the one unit you can rely on for accurate, verifiable comparisons.
What Is a Ratti?
Ratti is a much older, regionally rooted unit of weight, derived from the seeds of the Abrus precatorius plant, also called Gunja or Rakti. Long before precision scales existed, these small, fairly uniform seeds were used by Indian jewellers and astrologers as a practical way to measure gemstone weight.
Ratti remains deeply tied to Vedic astrology today — most gemstone recommendations from astrologers are still given in ratti rather than carat, since that's the unit classical astrological texts were written in.
Use Calculator: Carat to Ratti Calculator
Carat vs Ratti: Side-by-Side Comparison
| Parameter | Carat | Ratti |
|---|---|---|
| Origin | Carob seed (ancient Mediterranean trade) | Gunja/Abrus seed (ancient Indian trade) |
| Standardized Value | 1 carat = 200 mg | 1 ratti ≈ 182 mg (approx. 0.91 carat) |
| Recognition | International standard | Regional, mainly used in India |
| Used on Certificates | Yes, universally | No, certificates use carat |
| Used for Astrology | Rarely the primary unit | Standard unit in Vedic recommendations |
| Precision | Highly precise, divided into points | Traditionally less precise, being a natural-seed-based unit |
When Should You Use Carat, and When Ratti?
- Buying for astrological or planetary remedy purposes: Use ratti, since that's the unit your astrologer's recommendation is almost certainly based on — but always cross-check the equivalent carat value against the gemstone's lab certificate.
- Buying gemstone jewellery for fashion or investment: Use carat, since it's the internationally recognised, certificate-backed unit that makes comparing stones across sellers straightforward.
- Comparing prices between two sellers: Convert both to the same unit before comparing — a "5 ratti" stone and a "5 carat" stone are not remotely the same size, and treating them as equivalent is a common, costly mistake.
Final Thoughts
Carat and ratti aren't competing systems — they're two different traditions serving two different purposes. Carat gives you global standardisation and certificate accuracy; ratti connects you to centuries of Vedic astrological practice. The safest approach when buying any gemstone is simple: ask for the weight in both units, confirm it against the lab certificate, and never assume the numbers mean the same thing across sellers.
FAQs
Q1. What is the difference between carat and ratti?
Carat is the international standard unit for gemstone weight (1 carat = 200 mg), while ratti is a traditional Indian unit (1 ratti ≈ 0.91 carat) used mainly for astrological gemstone recommendations.
Q2. How many carats is 1 ratti?
1 ratti is approximately 0.91 carats, though the exact value can vary slightly depending on the regional standard used.
Q3. Why do astrologers recommend gemstone weight in ratti instead of carat?
Classical Vedic astrological texts were written using ratti as the unit of measurement, so astrologers continue to prescribe gemstone weight in ratti rather than carat.
Q4. Are gemstone certificates issued in carat or ratti?
Gemological certificates are always issued in carats, regardless of where the gemstone is sold, since carat is the universally accepted standard.
Q5. Is a 5 ratti gemstone the same as a 5 carat gemstone?
No, a 5 ratti gemstone is approximately 4.55 carats, so it's noticeably smaller than a 5 carat gemstone. Comparing the two directly is a common buying mistake.
Q6. Which unit should I use when buying a gemstone for astrology?
For astrological purposes, use the ratti weight recommended by your astrologer, but always cross-check the equivalent carat value against the gemstone's certificate before buying.
Q7. Does ratti value differ across regions in India?
Yes, some regions use a lighter local version of ratti, so it's important to confirm exactly what value a seller is using for one ratti before finalising a purchase.
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