# Millimeters to Astronomical Units (mm to au) Source: https://www.unitconvertercalculator.com/length/millimeters-to-astronomical-units/ **1 mm = 6.6845871222684E-15 au** One millimeter equals approximately 6.685 x 10-15 astronomical units. The Earth-Sun distance (1 AU) is about 149.6 trillion millimeters. The millimeter measures engineering precision; the AU measures planetary orbits. ## Formula Convert Millimeters to Astronomical Units ## Conversion Table | Millimeters (mm) | Astronomical Units (au) | |---|---| | 1 mm | 6.68458E-15 au | | 100 mm | 6.6845871E-13 au | | 10000 mm | 6.684587122E-11 au | | 1000000 mm | 6.68458712226E-9 au | | 100000000 mm | 6.6845871222684E-7 au | | 10000000000 mm | 6.6845871222684E-5 au | | 1000000000000 mm | 0.0066845871222684 au | | 100000000000000 mm | 0.66845871222684 au | | 10000000000000000 mm | 66.845871222684 au | ## Units ### Millimeter (mm) A metric unit of length equal to one thousandth of a meter. Used in engineering, manufacturing, and precise measurements. ### Astronomical Unit (au) Exactly 149,597,870,700 meters by IAU 2012 definition. Roughly the average distance from the Earth to the Sun. Used for distances within our solar system. ## Background 1 AU = 1.496 x 1014 mm (149.6 trillion). A 1 mm screw is 6.685 x 10-15 AU. The James Webb Space Telescope orbits at about 1.5 million km (1.5 x 1012 mm) from Earth, or about 0.01 AU. Its mirrors are aligned to millimeter precision at AU-scale distances. ## Good to Know The JWST's primary mirror segments must be aligned to within 10 nanometers (0.00001 mm) while orbiting 1.5 million km from Earth (0.01 AU). This is the ultimate mm-to-AU challenge: nanometer precision at astronomical distance. Engineering does not get harder than this. ## FAQ ### How many AU is 1 millimeter? One millimeter equals approximately 6.685 x 10-15 AU. ### How many millimeters are in 1 AU? One AU contains approximately 1.496 x 1014 mm (about 149.6 trillion). ### Is this conversion practical? In spacecraft engineering where instruments are aligned to millimeter precision at AU-scale distances. Mirror segments on space telescopes must be positioned to sub-millimeter accuracy while orbiting the Sun. ## Non-Frequently Asked Questions ### How many screws end-to-end reach the Sun? A typical M6x20 screw is 20 mm long. The Sun is 1.496 x 1014 mm away. That is 7.48 trillion screws. At $0.05 each, the screw highway costs $374 billion - roughly the GDP of Denmark. Danish screws to the Sun. ### How precise is spacecraft navigation in mm? The Mars rovers land within about 20 km of their target after traveling 225 million km (1.5 AU). That is 20,000,000 mm accuracy over 2.25 x 1014 mm of travel - precision of about 1 part in 11 million. Your GPS is accurate to about 3 m (3,000 mm). NASA is better. ### If the solar system were a clock face, how big would 1 mm be? Neptune orbits at about 30 AU. If that were a 30 cm clock, 1 AU = 1 cm and 1 mm = 0.1 AU = about 15 million km. On a solar-system clock, 1 mm represents 15 million kilometers. That is roughly 39 Moon distances per millimeter. Astronomical clocks do not tick in human-readable increments. ## Related Articles - [Why We Measure: The Deepest Urge in Human Civilisation](https://www.unitconvertercalculator.com/blog/why-we-measure) - [The Map Is Not the Territory: Why Every Measurement Is Wrong](https://www.unitconvertercalculator.com/blog/the-map-is-not-the-territory) - [Zero: The Most Dangerous Number in Measurement](https://www.unitconvertercalculator.com/blog/zero-the-most-dangerous-number-in-measurement) - [The Body as a Ruler: Every Measurement Unit That Came From Us](https://www.unitconvertercalculator.com/blog/the-body-as-a-ruler) - [The Speed of Everything: How We Measure From Glaciers to Light](https://www.unitconvertercalculator.com/blog/the-speed-of-everything) - [15 Obscure Measurement Units You've Never Heard Of (But Still Need)](https://www.unitconvertercalculator.com/blog/obscure-measurement-units-guide) - [When Measurements Go Wrong - Disasters, Blunders and Happy Accidents](https://www.unitconvertercalculator.com/blog/when-measurements-go-wrong) - [The Surprising Stories Behind Everyday Units of Measurement](https://www.unitconvertercalculator.com/blog/stories-behind-measurement-units) - [Metric vs. Imperial - The Complete Guide to the World's Two Measurement Systems](https://www.unitconvertercalculator.com/blog/metric-vs-imperial-complete-guide) - [Length & Distance Conversion Guide - Meters, Feet, Miles & Kilometers](https://www.unitconvertercalculator.com/blog/length-and-distance-guide) ## See Also - [Astronomical Units to Millimeters](https://www.unitconvertercalculator.com/length/astronomical-units-to-millimeters/)