Convert Inch to Astronomical Unit
Convert inches to astronomical units instantly. 1 inch = 1.697885e-13 astronomical unit — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Astronomical Unit to Inch converter for the reverse conversion.
Units explained
Inch
An inch is an Imperial and US customary unit of length defined since 1959 as exactly 25.4 millimeters (0.0254 meters). It is still the standard small unit of length in the United States, the United Kingdom (informally), and a few other countries.
The inch derives from the Roman uncia (one-twelfth of a foot) and survived through Anglo-Saxon and medieval English measurement systems. Various definitions persisted regionally until the 1959 International Yard and Pound Agreement standardized the inch globally as exactly 25.4 mm.
Inches are used in the US and UK for body height, screen sizes (TVs, monitors, phones), tire sizes, plumbing, lumber, paper sizes (US Letter is 8.5 × 11 in), and most consumer product specifications in the United States.
Anglo-Saxon origin (predating 1066); standardized to 25.4 mm exactly by the International Yard and Pound Agreement of 1959, signed by the US, UK, Canada, Australia, New Zealand, and South Africa.
Astronomical Unit
The astronomical unit (AU) is a unit of length equal to exactly 149,597,870,700 meters, approximately the average distance from Earth to the Sun. It is the fundamental unit for distance within the solar system.
The AU was originally defined as the semi-major axis of Earth's orbit. In 2012, IAU Resolution B2 redefined the AU as exactly 149,597,870,700 meters, severing its dependence on the actual fluctuating Earth–Sun distance.
AUs are used to express distances within the solar system (Mars: 1.5 AU, Pluto: ~40 AU at perihelion), exoplanet orbital radii, and other planetary-scale distances. Standard in planetary science and astronomy.
Original definition tied to Earth's orbit (Newton, 17th century); fixed at exactly 149,597,870,700 m by IAU Resolution B2 in 2012.
Inch to Astronomical Unit conversion formula
The relationship between inches and astronomical units:
To convert inches to astronomical units, multiply the value in inches by 1.697885e-13. To reverse, multiply astronomical units by 5.88968e+12.
How to use this converter
Type a value into the calculator. The result in astronomical units updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Astronomical Unit to Inch converter for the reverse direction.
Step-by-step: convert inches to astronomical units
- Write down the value in inches (in).
- Multiply that value by the factor 1.697885e-13.
- The product is the equivalent value in astronomical units (AU).
- To reverse, multiply the astronomical unit value by 5.88968e+12.
Worked examples
Example 1 — Convert 1 in to AU:
1 × 1.697885e-13 = 1.697885e-13 AU
Example 2 — Convert 100 in to AU:
100 × 1.697885e-13 = 1.697885e-11 AU
Real-world example — Hardware-scale dimensions
A 10-inch fastener or component is about as long as a thumbnail. Mechanics and DIY enthusiasts convert between inches and astronomical units daily when mixing metric and imperial tools.
10 in × 1.697885e-13 = 1.697885e-12 AU
Real-world example — Postcard and small-object dimensions
A postcard is about 5 inches wide. Converting to astronomical units is essential for international postal addressing forms that ask for dimensions in different units across countries.
5 in × 1.697885e-13 = 8.489426e-13 AU
Real-world example — Ruler-scale measurements
A 30-inch school ruler converts cleanly to astronomical units — useful when buying a desk accessory from a retailer whose product specs use a different unit.
30 in × 1.697885e-13 = 5.093655e-12 AU
Inch to Astronomical Unit conversion table
Standard reference values for converting inches to astronomical units:
| Inch [in] | Astronomical Unit [AU] |
|---|---|
| 0.01 | 1.697885e-15 |
| 0.1 | 1.697885e-14 |
| 1 | 1.697885e-13 |
| 2 | 3.39577e-13 |
| 3 | 5.093655e-13 |
| 4 | 6.791541e-13 |
| 5 | 8.489426e-13 |
| 10 | 1.697885e-12 |
| 20 | 3.39577e-12 |
| 30 | 5.093655e-12 |
| 40 | 6.791541e-12 |
| 50 | 8.489426e-12 |
| 100 | 1.697885e-11 |
| 500 | 8.489426e-11 |
| 1000 | 1.697885e-10 |
Frequently asked questions
How many astronomical units is 1 inch?
How do I convert inches to astronomical units?
How do I convert astronomical units back to inches?
How many astronomical units is 100 inches?
Popular length unit conversions
Convert Inch to other length units
Show all Inch conversions
Metric / SI (18 units)
Imperial / US Customary (26 units)
Nautical (1 units)
Astronomical (9 units)
Atomic / Physics (6 units)
Typographic (3 units)
Sources & references
Conversion factor (1 in = 1.697885e-13 AU) verified against the following authoritative sources:
- BIPM — The International System of Units (SI Brochure 9th ed.)
Official BIPM publication defining the seven SI base units (including the meter) and the rules for their use. The global authority on units of measurement.
- NIST — Guide to the SI
US National Institute of Standards and Technology reference covering the SI base and derived units with definitions and usage rules for US technical practice.
- NIST Special Publication 811 — Guide for the Use of the International System of Units
Detailed NIST guide covering exact conversion factors between SI and US customary units along with formatting and rounding conventions.
- NIST — Refinement of values for the yard and pound (Federal Register 1959)
The treaty (signed by US
- International Astronomical Union — System of Astronomical Constants
The IAU defines astronomical units including the AU (149597870700 m exactly) light-year and parsec used in astronomy and astrophysics.