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Convert Obolus to Grain (ob to gr) 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.
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.
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.