Astronomical Unit (AU

An Astronomical Unit (AU) is defined as exactly 149,597,870,700 meters (~149.6 million km), representing the mean distance from Earth to the Sun. It serves as the fundamental yardstick for measuring distances within our Solar System.

To use the Astronomical Unit (AU) & Space Distance Converter, enter your Distance Value, Unit to Convert From. The calculator instantly computes Astronomical Units (AU), Kilometers (km) and more. Results update in real time as you change any input — no submit button needed.

How to Use This Calculator

Enter your Distance Value (e.g. 1) and Unit to Convert From — choose from Astronomical Units (AU), Kilometers (km), Miles (mi). Results update instantly as you type — adjust any value to compare scenarios.

The Formula

1 AU = 149,597,870.7 km ≈ 92,955,807 miles

1 Light-Year = 63,241.077 AU ≈ 9.461 × 10¹² km

1 Parsec = 206,264.806 AU ≈ 3.2616 Light-Years

Speed of Light = 299,792.458 km/s (1 AU light travel time = 8 min 20 sec)

Worked Example

Convert 1 AU (Earth-Sun distance):

1 AU = 149,597,870.7 km = 92,955,807 miles = 0.00001581 light-years.

Light Travel Time = 8 minutes and 20.0 seconds.

Understanding Your Result

Unit conversions are exact by definition within a given measurement system (e.g., 1 km = exactly 1,000 m). Cross-system conversions (metric to imperial) use defined exchange factors: 1 inch = exactly 2.54 cm; 1 pound = 0.45359237 kg. Round your converted result to match the precision of your original measurement — expressing more decimal places than your input justifies implies false accuracy. For regulatory, legal, or safety-critical applications, verify which measurement system is required by the applicable standard.