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Convert Light Year to Millimeter (ly to mm) instantly with accurate, readable results.
Use our Length Unit Converter to quickly convert between meters, kilometers, feet, inches, miles, and more. This powerful unit conversion tool supports both metric and imperial systems, making it ideal for travel, engineering, education, and everyday use. Whether you're calculating distances or comparing measurements, our length unit conversion calculator ensures fast and accurate results every time.
Light-year (ly) - astronomical distance
Light-year is an astronomical distance equal to the distance light travels in vacuum in one Julian year. Used for interstellar and intergalactic scales; based on c = 299,792,458 m/s and a Julian year of 365.25 days (31,557,600 s)
- Symbol: ly
- System: Astronomical (non-SI, accepted for use with SI)
- Defined relation: 1 ly = c × 31,557,600 s = 9.4607304725808×10^15 m ≈ 9.4607×10^12 km
- Other relations: 1 ly ≈ 63,241.077 AU; 1 ly ≈ 0.306601 pc; 1 pc ≈ 3.26156 ly
- Typical examples: Proxima Centauri ~4.2465 ly; Milky Way diameter ~1.0×10^5 ly; Andromeda Galaxy ~2.5×10^6 ly
Millimeter (mm) — one thousandth of a meter
Used for precision work, machining, and rainfall depth reporting. Suitable for tolerances and tiny parts.
- Symbol: mm
- System: SI derived unit
- Exact relations: 1 mm = 0.001 m = 0.1 cm
- Imperial/US equivalents: 1 mm = 0.0393700787 in
- Typical examples: screw diameters, gasket thickness, PCB traces