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Conversion Formula:
Convert Grain to Milligram (gr to mg) instantly with accurate, readable results.
Use our Mass Unit Converter to convert between grams, kilograms, pounds, ounces, and other weight units instantly. Designed for cooking, science, fitness, and engineering needs, this unit conversion tool offers accurate results between metric and imperial systems. Whether you’re tracking body weight, measuring ingredients, or handling heavy machinery, our mass unit conversion calculator has you covered.
Grain (gr) — a small imperial and US customary unit of mass
It is defined as exactly 1/7000 of an avoirdupois pound; since 1 lb = 0.45359237 kg exactly, 1 gr = 64.79891 mg exactly. Used mainly for measuring bullets, gunpowder, arrows, and some pharmaceutical or historical masses.
- Symbol: gr
- System: Imperial and US customary unit for mass
- Exact relations: 1 gr = 1/7000 lb = 1/437.5 oz = 64.79891 mg
- Metric equivalents: 1 gr = 0.06479891 g ≈ 0.0000647989 kg
- Typical examples: a small bullet ~40 gr; a larger rifle bullet ~150 gr; an aspirin tablet was historically 5 gr.
Milligram (mg) — a small SI unit of mass
It is defined as one thousandth of a gram, or one millionth of a kilogram, the SI base unit for mass. Used worldwide for measuring very small masses in medicine, nutrition, chemistry, laboratory work, supplements, and precise product labeling.
- Symbol: mg
- System: SI unit for mass; decimal submultiple of the kilogram
- Exact relations: 1 mg = 0.001 g = 0.000001 kg = 1000 µg
- Imperial equivalents (derived from 1 lb = 0.45359237 kg exactly): 1 mg ≈ 0.000035274 oz ≈ 0.00000220462 lb
- Typical examples: a medicine dose ~200 mg; a vitamin tablet ~500 mg; a small grain of salt less than 1 mg.