Grain to Milligrams (mg) Converter
1 grain = 64.799 mg
How to Convert Grains to Milligrams
Medical note: In pharmacy, "gr" means grain (64.8 mg). Do not confuse with "g" (gram = 1,000 mg). A prescription for "gr v" means 5 grains = 325 mg — the same as standard aspirin.
Where Grains Are Used
| Application | Example | Grains | mg |
|---|---|---|---|
| Aspirin (standard) | Regular-strength | 5 gr | 325 mg |
| Aspirin (extra strength) | Extra-strength | 7.7 gr | 500 mg |
| Nitroglycerin (low dose) | Heart medication | 1/150 gr | 0.4 mg |
| Bullet — 9mm standard | Ammunition | 115 gr | 7,452 mg |
| Bullet — .45 ACP | Ammunition | 230 gr | 14,904 mg |
| Arrow — target | Archery | 400 gr | 25,920 mg |
Grain to mg Reference Table
| Grains (gr) | Milligrams (mg) | Grams (g) |
|---|---|---|
| 0.25 gr | 16.2 mg | 0.0162 g |
| 0.5 gr | 32.4 mg | 0.0324 g |
| 1 gr | 64.799 mg | 0.0648 g |
| 1.5 gr | 97.198 mg | 0.0972 g |
| 2 gr | 129.598 mg | 0.1296 g |
| 2.5 gr | 161.997 mg | 0.162 g |
| 3 gr | 194.397 mg | 0.1944 g |
| 4 gr | 259.196 mg | 0.2592 g |
| 5 gr | 323.995 mg | 0.32399 g |
| 6 gr | 388.793 mg | 0.38879 g |
| 7 gr | 453.592 mg | 0.45359 g |
| 8 gr | 518.391 mg | 0.51839 g |
| 9 gr | 583.19 mg | 0.58319 g |
| 10 gr | 647.989 mg | 0.64799 g |
| 15 gr | 971.984 mg | 0.97198 g |
| 20 gr | 1295.978 mg | 1.29598 g |
| 25 gr | 1619.973 mg | 1.61997 g |
| 30 gr | 1943.967 mg | 1.94397 g |
| 50 gr | 3239.946 mg | 3.23995 g |
| 100 gr | 6479.891 mg | 6.47989 g |
Weight Unit Comparison
| Unit | = mg | = grains |
|---|---|---|
| 1 grain (gr) | 64.799 mg | 1 gr |
| 1 milligram (mg) | 1 mg | 0.01543 gr |
| 1 gram (g) | 1,000 mg | 15.432 gr |
| 1 ounce (oz) | 28,349.5 mg | 437.5 gr |
| 1 pound (lb) | 453,592 mg | 7,000 gr |
Frequently Asked Questions
How many mg is 1 grain?
1 grain = 64.79891 mg exactly. For everyday use, 1 grain ≈ 65 mg. This unit comes from the weight of a single grain of wheat.
What is 5 grains in mg?
5 grains = 323.99 mg ≈ 324 mg. This is the weight of a standard aspirin tablet. Old pharmacy labels wrote "gr v" (5 grains) before metric became standard.
What is 325 mg in grains?
325 mg ÷ 64.79891 = 5.015 grains ≈ 5 grains. Standard aspirin is labeled 325 mg = 5 grains.
Is "gr" grain or gram?
"gr" = grain (64.8 mg). "g" = gram (1,000 mg). In medical contexts, always check which abbreviation is used — confusing the two could be dangerous. Modern prescriptions use metric (mg, g) to avoid this confusion.
How many grains in a pound?
There are exactly 7,000 grains in 1 avoirdupois pound. 1 pound = 453.592 grams = 453,592 mg = 7,000 grains.