Stone to Milligrams (st to mg)

1 stone equals 6,350,293.18 milligrams exactly.

1 stone = 6,350,293.18 milligrams

How to convert stone to milligrams

To convert stone to milligrams, multiply the number of stone by 6,350,293.18. This factor is exact. To go the other way, multiply milligrams by 1.574730444×10⁻⁷ (rounded).

milligrams = stone × 6,350,293.18

Example: 10 stone = 63,502,931.8 milligrams.

About these units

Stone (st)

Imperial (British)Current unit

14 pounds (6.35 kg). Still the everyday unit for body weight in the UK and Ireland.

As the name says, the first stones were literal stones. People used them as weights, and surviving examples include Roman-era pieces made in multiples of the Roman pound and a 16th-century bronze one-stone weight bearing the English royal arms. The size was not fixed: a statute of about 1300 gave 5 pounds for glass, 8 for sugar and spices and 12 for lead, while in 1772 the Encyclopaedia Britannica noted that a stone of beef was 8 pounds in London, 12 in Hertfordshire and 16 in Scotland. Edward III set 14 pounds for wool and other goods in 1350.

The Weights and Measures Act 1835 clarified the legal trade units, with 14 pounds to the stone and 28 to the quarter. Trade use ended with metrication, in Ireland in 1983 and in the UK with the Weights and Measures Act 1985, yet the stone refuses to die. In Britain and Ireland people still say they weigh 11 stone 4, meaning 11 stone plus 4 pounds, or about 71.7 kg. It is also used in sports such as boxing, wrestling and horse racing. A single stone, at 6.35 kg, is a convenient chunk of body weight to talk about.

1 stone = 6.35029318 kilograms (exactly).

Sources: Wikipedia: Stone (unit); NIST Guide to the SI, Appendix B.8 (mass conversions)

Milligram (mg)

Metric (SI)Current unit

One thousandth of a gram. Used for medicine doses and vitamins.

No single inventor can be credited with the milligram. It arrived with the metric system that France introduced in the 1790s, where the gram was the basic unit of mass and thousandths of it were named with a prefix. When the International System of Units was later built around the kilogram, the rule against stacked prefixes meant that a millionth of a kilogram is written 1 mg, never a microkilogram, so the milligram remained a gram-based unit even though the gram itself is not the SI base.

A milligram is small enough that doses of medicine and vitamins are measured in it routinely. A US penny weighs about 2.5 g, so a milligram is roughly one 2,500th of a coin. The unit is also at the center of a well-known safety problem: milligram and microgram differ by a factor of 1,000, and the abbreviation mcg for micrograms is used on prescriptions precisely so that a handwritten micro sign cannot be misread as milli. Confusing the two has caused serious medication errors.

1 milligram = 0.000001 kilograms (exactly).

Sources: Wikipedia: Milligram; Wikipedia: Microgram; Wikipedia: Gram

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