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Convert Milligram to Obolus (mg to ob) 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.
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.
Obolus (obol) — a historical unit of mass equal to 10 grains
It is commonly treated as half a scruple, or 10 grains, in historical Roman and apothecaries’ weight contexts; because the obolus was also a coin and ancient weight term, its exact value can vary by period and region. Used mainly in historical medicine, pharmacy, numismatics, and references to ancient or apothecaries’ measures.
- Symbol: obol, obolus
- System: Historical Roman and apothecaries’ unit for mass
- Exact relations: 1 obolus = 1/2 scruple = 10 gr = 647.9891 mg
- Metric equivalents: 1 obolus = 0.6479891 g ≈ 0.000647989 kg
- Typical examples: historical prescriptions may mention oboli; 2 oboli equals scruple; 1 obolus is a little less than 2/3 of a gram.