Feet to Astronomical Units (ft to au)

1 foot equals 2.037462155×10⁻¹² astronomical units (rounded).

1 foot = 2.037462155×10⁻¹² astronomical units

How to convert feet to astronomical units

To convert feet to astronomical units, multiply the number of feet by 2.037462155×10⁻¹². The factor is rounded to 10 significant digits. To go the other way, multiply astronomical units by 490,806,662,402 (rounded).

astronomical units = feet × 2.037462155×10⁻¹²

Example: 10 feet = 2.037462155×10⁻¹¹ astronomical units.

About these units

Foot (ft)

US & ImperialCurrent unit

12 inches. Defined as exactly 0.3048 meters. Still the standard unit for height, altitude in aviation and room dimensions in the US and UK.

Human anatomy supplied the idea: an adult foot is roughly 15 percent of body height. Ancient cultures turned that into standards, but not the same one. The Greek pous was about 302 mm, the standard Roman pes about 295.7 mm, and a Harappan foot of about 335 mm has been reported from the Indus Valley. Historically, a foot fell somewhere between about 250 and 335 mm. Charlemagne tried to standardize units around 790 with little lasting success, and in 1593 English law fixed the statute mile at 5,280 feet.

The modern foot dates from the 1959 International Yard and Pound Agreement, which defined the yard as exactly 0.9144 meter and so the foot as exactly 0.3048 meter; the UK adopted it on 1 January 1964. The US survey foot, defined in 1893 as 1200/3937 meter, was deprecated on 31 December 2022. Feet remain in everyday use for height and rooms in the US, and ISO shipping containers are defined in them. Aviation altitudes use them too: flight level 330 means 33,000 feet.

1 foot = 0.3048 meters (exactly).

Sources: Wikipedia: Foot (unit); Wikipedia: Mile; NIST Guide to the SI, Appendix B.8: conversion factors

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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