Convert Grain to Carat (gr → ct)
The grain is the smallest traditional weight unit, used in pharmaceutical compounding, ammunition, and arrow tips.
Grain to Carat Conversion Table
10 common values| Grain | Carat |
|---|---|
| 1 gr | 0.323995 ct |
| 5 gr | 1.619973 ct |
| 10 gr | 3.239946 ct |
| 25 gr | 8.099864 ct |
| 50 gr | 16.199727 ct |
| 100 gr | 32.399455 ct |
| 250 gr | 80.998638 ct |
| 500 gr | 161.99728 ct |
| 1,000 gr | 323.99455 ct |
| 5,000 gr | 1,619.9727 ct |
How to Convert Grain to Carat Manually
Step by StepConverting grains to carats is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.
- 1Take your value in grainsStart with the number of grains (gr) you want to convert.
- 2Multiply by 0.323995The conversion factor from gr to ct is 0.323995. Multiply your value by this number.
- 3Read the result in caratsThe result is your value in carats (ct).
Formula
Multiply the value in grains by 0.323995. For the reverse direction, multiply by 3.086472.
ct = gr × 0.323995gr = ct × 3.086472Tips
Use these in everyday conversions- 1 grain = 64.79891 mg exactly. 7000 grains = 1 pound.
- Ballistics is one of the few modern contexts where grains are essential.
- Some older pharmacology dosing survives in grain units — 5 gr ≈ 325 mg.
Common Mistakes
Avoid these- Confusing the grain (mass) with the troy grain in older precious-metal contexts — they are identical (64.8 mg).
- Assuming "grain" refers to an amount of cereal — in firearms it is always a weight.
- Reading "5 gr" as 5 grams — it is 5 grains (324 mg).
About Grain and Carat
What is the Grain?
The grain equals exactly 64.79891 milligrams (0.06479891 g) and is the smallest unit in the traditional avoirdupois weight system. Originally based on the average mass of a single grain of wheat or barley, the unit was standardized to its current value with the 1959 international yard and pound agreement. The grain is still used in pharmaceutical compounding (some older drug formulations specify grains, especially aspirin and codeine), arrow tips and ammunition (bullet weights are commonly given in grains — a 9 mm bullet is around 115 grains), and precious-metal weighing (one troy ounce = 480 grains). It relates to the ounce (437.5 grains = 1 oz avoirdupois), the pound (7,000 grains = 1 lb), and the milligram (1 grain ≈ 64.8 mg). The unit reflects medieval agriculture's role in shaping early measurement systems.
- Bullet and gunpowder mass in ballistics
- Older pharmaceutical dosing in Anglo-Saxon countries
- Arrow shaft and archery equipment weights
A 9 mm bullet typically weighs 115–124 grains (7.45–8.03 g). Aspirin grain dosing: "5 grain aspirin" = 325 mg.
What is the Carat?
The carat equals exactly 200 milligrams (0.2 g) and is the universal unit for gemstone and diamond weight in the global jewelry industry. The word derives from the Greek 'keration' and the Arabic 'qīrāṭ,' both referring to carob seeds, which were once used as natural counterweights for weighing gems because they have remarkably uniform mass. The metric carat was standardized in 1907 at exactly 200 mg, replacing dozens of regional carat values that had varied between 188 and 213 mg. A 1-carat diamond is roughly 6.5 mm in diameter, and the famous Hope Diamond weighs 45.52 carats. The carat is distinct from the karat (with a 'k'), which measures gold purity (24-karat = 100% gold). It relates to the gram (5 ct = 1 g) and the milligram (200 mg = 1 ct). Gem dealers commonly use 'points' for fractions (100 points = 1 carat).
- Diamond and gemstone retail and valuation
- Jewellery manufacturing and design
- International gem certification (GIA, IGI)
A 1-carat diamond weighs 200 mg and is typically 6.5 mm across. The Hope Diamond is 45.52 carats (9.1 g).