Grains to Kilograms (gr to kg)

1 grain equals 0.00006479891 kilograms exactly.

1 grain = 0.00006479891 kilograms

How to convert grains to kilograms

To convert grains to kilograms, multiply the number of grains by 0.00006479891. This factor is exact. To go the other way, multiply kilograms by 15,432.35835 (rounded).

kilograms = grains × 0.00006479891

Example: 10 grains = 0.0006479891 kilograms.

About these units

Grain (gr)

US & ImperialTraditional unit (still used in some regions)

Exactly 64.79891 mg, based on the weight of a grain of barley. Still used for the weight of bullets, arrows and some medicines.

Barley and wheat seeds served as the earliest common weights in the Mediterranean, because a dry seed is small and fairly consistent. Medieval English law tied weights to the average mass of such grains, and the name grain stuck even after the link to actual cereal faded. The unit is exactly 64.79891 milligrams, fixed by the 1959 international yard and pound agreement, and NIST lists the same figure of 6.479891 x 10^-5 kilogram as exact.

Grain is unusual in being identical in the troy, avoirdupois and apothecaries' systems. A troy pound has 5,760 grains and an avoirdupois pound has 7,000. Modern use is mostly in niches: bullet and propellant weights, arrow weights in archery, and water hardness expressed as grains per gallon. Older drug doses were also given this way, with a standard 325 milligram aspirin tablet equal to five grains. Jewelers once used a pearl grain, a quarter of a carat. In the United Kingdom the unit has no legal standing for trade.

1 grain = 0.00006479891 kilograms (exactly).

Sources: Wikipedia: Grain (unit); NIST SP 811 Appendix B.8 (conversion factors)

Kilogram (kg)

Metric (SI)Current unit

The SI base unit of mass. Since 2019 it is defined by fixing the value of the Planck constant, replacing the old platinum-iridium cylinder in Paris.

Oddly for a base unit, the kilogram began life as a derived one. In 1793 revolutionary France defined the grave as the mass of one litre of water, and a decree of 1795 then replaced it with the kilogramme, a name built from the Greek khilioi (a thousand) and gramma, a Late Latin word for a small weight. In 1799 a platinum cylinder, the Kilogramme des Archives, became the physical standard, matching a cubic decimetre of water at its densest, around 4 degrees Celsius. In 1889 the metric community adopted a platinum-iridium cylinder made in 1879, the International Prototype of the Kilogram, nicknamed Le Grand K.

The kilogram is still the only SI base unit with a prefix in its name. Because SI forbids stacked prefixes, a millionth of a kilogram is a milligram rather than a microkilogram, so every mass prefix is attached to the gram. Calibrating every national standard against one object in a vault near Paris meant that all of them drifted relative to it, so in November 2018 member states voted to tie the kilogram to a fixed value of the Planck constant. The change took effect on 20 May 2019. Day to day nothing shifted, but the definition no longer depends on a single piece of metal.

The kilogram is the reference unit for weight & mass on this site.

Sources: NIST: Kilogram introduction (SI redefinition); Wikipedia: Kilogram

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