Convert length and distance units — meters, feet, inches, kilometers, miles, light years and more.
| Unit | Name | Value |
|---|---|---|
| 0.001 mm | 6.684e-18 au | |
| 0.01 mm | 6.684e-17 au | |
| 0.1 mm | 6.684e-16 au | |
| 1 mm | 6.684e-15 au | |
| 5 mm | 3.342e-14 au | |
| 10 mm | 6.684e-14 au | |
| 50 mm | 3.342e-13 au | |
| 100 mm | 6.684e-13 au | |
| 1000 mm | 6.684e-12 au |
Multiply the number of Millimeters by 6.6845×10-15 to get Astronomical Units. Formula: au = mm × 6.6845×10-15. Example: 10 mm × 6.6845×10-15 = 6.6845×10-14 au. To reverse, divide Astronomical Units by 6.6845×10-15 to get Millimeters.
| Millimeter (mm) | Astronomical Unit (au) |
|---|---|
| 0.001 mm | 6.6845×10-18 au |
| 0.01 mm | 6.6845×10-17 au |
| 0.1 mm | 6.6845×10-16 au |
| 0.5 mm | 3.3422×10-15 au |
| 1 mm | 6.6845×10-15 au |
| 2 mm | 1.3369×10-14 au |
| 5 mm | 3.3422×10-14 au |
| 10 mm | 6.6845×10-14 au |
| 20 mm | 1.3369×10-13 au |
| 50 mm | 3.3422×10-13 au |
| 100 mm | 6.6845×10-13 au |
| 250 mm | 1.6711×10-12 au |
| 500 mm | 3.3422×10-12 au |
| 1000 mm | 6.6845×10-12 au |
| 10000 mm | 6.6845×10-11 au |
To convert Millimeter to Astronomical Unit, multiply by 6.6845×10-15. Example: 10 mm = 6.6845×10-14 au
To convert Astronomical Unit back to Millimeter, divide by 6.6845×10-15 (multiply by 1.496×1014). Use the swap button above.
Start with 100 Millimeters = 6.6845×10-13 au as your reference point. Scale up or down from there.
Solar telescope mirror dimensions and focal lengths use millimetres while the Sun's distance (1 AU) and planetary positions use AU. Engineers and astronomers bridge both scales in every instrument design and observation plan.
1 AU = 1.496×10¹⁴ mm — 149.6 trillion millimetres. Physics teachers use this to make the Earth-Sun distance tangible: "The Sun is 149.6 trillion millimetre-rulers away — impossible to visualise, which is exactly the point."
Space telescope focal plane arrays are dimensioned in millimetres while observational targets use AU distances. Engineers convert between mm-scale detector geometry and AU-scale orbital positions for every pointing and focus calculation.
Solar physics calculations in CGS use centimetres but distances are often discussed in AU. Physicists converting solar instrument mm dimensions to AU for scale context work across the full range of solar physics measurement scales.
Spacecraft dimensions for planetary defence missions use millimetres while intercept distances and asteroid orbit radii use AU — mission engineers convert between mm spacecraft specs and AU orbital parameters in every mission design.
Comprehensive converters include mm-to-AU for researchers who need to contextualise mm-scale instrument or particle dimensions against AU-scale solar system distances in multi-scale research publications.
The Millimeter is a unit of Length measurement (symbol: mm). 1 mm = 6.6845×10-15 au. Used in scientific and practical Length measurement applications.
The Astronomical Unit is a unit of Length measurement (symbol: au). It is part of an internationally recognised measurement system used alongside the Millimeter.
The millimetre was introduced alongside the metre in 1795 as part of the French metric system — one-thousandth of a metre, from the Latin 'mille' (thousand). Its practical importance emerged during the Industrial Revolution, when manufacturing tolerances first needed sub-centimetre precision. By the 20th century, ISO engineering drawing standards adopted millimetres as the primary dimension unit for all technical drawings worldwide. Today millimetres are the universal language of engineering — from the finest watch gear to the largest aircraft fuselage — and are the most widely used length unit in global manufacturing.
The astronomical unit has ancient roots — Aristarchus of Samos attempted to measure the Earth-Sun distance around 270 BC. For centuries the AU was estimated using Venus transit observations. Edmond Halley organised the first coordinated international transit-of-Venus expedition in 1716. The modern value was determined by radar ranging to Venus in 1961. The IAU formally defined the AU as exactly 149,597,870,700 metres in 2012 — a fixed constant of physics.
Common use: Millimeter to Astronomical Unit conversion is needed when working with international standards, scientific publications, or reference materials that use different unit systems for Length measurement.