Meters to Astronomical Units (m to au)

1 meter equals 6.684587122×10⁻¹² astronomical units (rounded).

1 meter = 6.684587122×10⁻¹² astronomical units

How to convert meters to astronomical units

To convert meters to astronomical units, multiply the number of meters by 6.684587122×10⁻¹². The factor is rounded to 10 significant digits. To go the other way, multiply astronomical units by 149,597,870,700.

astronomical units = meters × 6.684587122×10⁻¹²

Example: 10 meters = 6.684587122×10⁻¹¹ astronomical units.

About these units

Meter (m)

Metric (SI)Current unit

The SI base unit of length. Since 1983 it is defined as the distance light travels in a vacuum in 1/299,792,458 of a second.

Meter comes from the Greek metron, a measure. In 1791 the French National Assembly defined it as one ten-millionth of the distance from the equator to the North Pole along a great circle through Paris, after rejecting the length of a seconds pendulum because that length changes with local gravity. The surveyors Delambre and Méchain measured the meridian arc, and in 1799 a platinum bar known as the Mètre des Archives became the physical standard. NIST notes that this Earth-based meter turned out to be about 0.2 mm shorter than the true pole-to-equator fraction it was meant to represent.

The 1875 Treaty of the Meter created the CGPM and the BIPM to look after common standards, and in 1889 a platinum-iridium prototype bar took over; the original is still kept at the BIPM. In 1960 the meter was tied to 1,650,763.73 wavelengths of an orange-red krypton-86 line, and in 1983 to the speed of light, which made length a quantity derived from the time standard. The 2018 revision reworded that definition without changing the meter's size. NIST offers a handy yardstick for scale: a pace, meaning two steps, is roughly a meter or a yard.

The meter is the reference unit for length on this site.

Sources: BIPM: history of the metre; NIST: the meter and the SI redefinition; Wikipedia: Metre

Astronomical Unit (au)

AstronomicalCurrent unit

Exactly 149,597,870,700 meters, roughly the average distance from the Earth to the Sun. Used for distances within the solar system.

Astronomers began calling it the astronomical unit in the mid-nineteenth century, with the name first recorded in 1848, though the quantity itself had been chased since antiquity. Aristarchus put the Sun 18 to 20 times farther away than the Moon, when the true ratio is about 389. Cassini and Richer used the parallax of Mars in 1672, transits of Venus served for generations, and radar echoes from Venus and Mars in the early 1960s finally gave direct distances.

For most of the twentieth century the unit was tied to the Gaussian gravitational constant, which meant its value had to be remeasured as observations improved. In 2012 the IAU removed that dependence by fixing it at exactly 149,597,870,700 meters and recommending the symbol au. The figure used here is that exact value. It is close to the mean Earth-Sun separation, which varies from about 0.983 au at perihelion to about 1.017 au at aphelion. Light needs roughly 499 seconds to cross one au, and Neptune orbits at about 30 au.

1 astronomical unit = 149,597,870,700 meters (exactly).

Sources: Wikipedia: Astronomical unit; NIST SP 811 Appendix B.8: factors for units outside the SI; Wikipedia: Light-second

Related conversions

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