Convert grains to milligrams for pharmaceutical dosing, ammunition reloading, and precious metal weighing. Accurate calculator with precision conversion factor 64.79891 mg per grain.
1 grain equals 64.7987351286903 milligram
Formula: mg = gr × 64.7989
The grain-to-milligram conversion is essential for professionals requiring extreme precision in weight measurement. With 1 grain equaling exactly 64.79891 milligrams, this conversion bridges the imperial apothecaries' system and the metric system. Understanding this relationship is critical in pharmacy, ammunition reloading, and jewelry industries where even small measurement errors can have significant consequences.
Pharmaceutical accuracy directly impacts patient safety—incorrect grain-to-milligram conversions can result in dangerous overdoses or ineffective treatments. In ammunition reloading, precision is critical for firearm safety and ballistic consistency. For precious metals and gemstones, accurate weight conversion affects pricing and authenticity verification. A single grain error (64.8 mg) can mean the difference between a therapeutic dose and a toxic one, or between a safe ammunition load and a dangerous one.
Pharmacists and physicians use grain-to-milligram conversions when interpreting historical prescriptions, calculating pediatric dosages from older formulations, and ensuring medication accuracy across international healthcare systems. Many established medications, particularly aspirin and certain cardiac medications, were originally formulated in grains. Converting these to milligrams ensures precise modern dosing without medication errors that could harm patients.
Reloaders measure gunpowder charges in grains to achieve precise ballistic performance and firearm safety. Powder scales display measurements in grains, and reloading manuals specify charges in grains. Converting to milligrams helps reloaders cross-reference international ballistics data, verify scale accuracy, and document loads for safety records. Precision in this conversion is critical—a 1-grain error in powder charge can significantly affect bullet velocity and firearm safety.
| grains | milligrams |
|---|---|
| 1 gr | 64.798735 mg |
| 5 gr | 323.993676 mg |
| 10 gr | 647.987351 mg |
| 50 gr | 3239.936756 mg |
| 100 gr | 6479.873513 mg |
Formula: mg = gr × conversion factor
The grain is a widely used unit for measuring weight. It is commonly used in various applications and industries worldwide.
The milligram is a widely used unit for measuring weight. It is commonly used in various applications and industries worldwide.
This grain to milligram converter uses high-precision conversion factors to ensure accurate results for professional and academic use.
Our calculator provides results with up to 10 decimal places for maximum accuracy.
Exactly 64.79891 milligrams equal one grain. This precise conversion was established internationally in 1959 when 1 pound avoirdupois was defined as exactly 453.59237 grams, making 1 grain (1/7000 of a pound) precisely 64.79891 mg. In pharmaceutical and ammunition contexts, this precision is essential—rounding to 65 mg creates a 0.3% error that compounds dangerously in dosing calculations.
Historical momentum and precision requirements maintain grain usage in these specialized fields. Pharmaceutical references dating back decades specify medications in grains, and reloading manuals use grains because powder scales were originally calibrated in grains. Additionally, the grain provides convenient whole-number measurements for typical doses and powder charges—5 grains for aspirin, 45 grains for rifle powder—whereas metric equivalents produce awkward decimals. Professional standards in these industries maintain grain measurements for consistency and safety.
Browse our collection of 6 Weight converters. Each converter provides instant, accurate results for professional and academic use.