Convert Grains to Carats
Convert Grains (gr) to Carats (ct) instantly and accurately.
Conversion Formula
ct = gr × 0.32399455
About Grains
A grain (gr) is the smallest unit in both the avoirdupois and troy weight systems, equal to exactly 64.79891 milligrams. Originally defined as the mass of a single grain of barley or wheat from the middle of an ear, it has been a standard of weight since ancient times. Today, grains are used to weigh gunpowder charges and bullets (a standard .308 rifle bullet weighs 168 gr), pharmaceutical preparations in apothecary compounding, and the fineness of gold alloys. Arrowhead and fishing hook weights are also specified in grains.
About Carats
A metric carat (ct or CD) is exactly 200 milligrams (0.2 g), the universal standard for weighing gemstones. Established internationally in 1907, it replaced fractionally different regional carat weights previously used in different countries. The total weight of a diamond or colored gemstone is always expressed in carats: a 1.00 ct diamond of excellent cut and color can command over $5,000. The Cullinan diamond, the largest gem-quality rough diamond ever found, weighed 3,106.75 carats.
Quick Reference Table
| Grains (gr) | Carats (ct) |
|---|---|
| 1 gr | 0.323995 ct |
| 2 gr | 0.647989 ct |
| 5 gr | 1.61997 ct |
| 10 gr | 3.23995 ct |
| 25 gr | 8.09986 ct |
| 50 gr | 16.1997 ct |
| 100 gr | 32.3995 ct |