Kilograms to Solar Masses (kg to M☉)

1 kilogram equals 5.02899214×10⁻³¹ solar masses (rounded).

1 kilogram = 5.02899214×10⁻³¹ solar masses

How to convert kilograms to solar masses

To convert kilograms to solar masses, multiply the number of kilograms by 5.02899214×10⁻³¹. The factor is rounded to 10 significant digits. To go the other way, multiply solar masses by 1.98847×10³⁰.

solar masses = kilograms × 5.02899214×10⁻³¹

Example: 10 kilograms = 5.02899214×10⁻³⁰ solar masses.

Approximate value. Standards for the solar mass varied by place and period, so this converter uses the most commonly cited value. Treat results as estimates, not exact figures.

About these units

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

Solar Mass (M☉)

AstronomicalCurrent unitApproximate value

About 1.988×10³⁰ kg, the mass of the Sun (roughly 332,946 Earths). Used for stars and galaxies.

The solar mass is the mass of the Sun used as the standard weight for stars, black holes and galaxies. The best estimate is about 1.98847 x 10^30 kg, with an uncertainty near 0.005 percent, while the International Astronomical Union's nominal value is 1.988416 x 10^30 kg. That is about 332,946 Earth masses, commonly rounded to 333,000.

Isaac Newton made the first known estimate in the Principia of 1687, putting the Earth to Sun mass ratio at about 1 to 28,700. In the third edition he revised this to 1 to 169,282 after finding that his solar parallax was faulty. Transits of Venus in 1761 and 1769 later improved the Sun's distance, and Cavendish's 1798 measurement gave a usable value of G.

The unit predates precise values of G and the astronomical unit, and it survives because Kepler's third law lets astronomers compute the masses of planets and binary stars directly from orbital data in solar units. The product GM of the Sun is known far better than the mass itself.

1 solar mass = 1.98847×10³⁰ kilograms (approximately).

Sources: Wikipedia: Solar mass

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