Millimeters to Parsecs (mm to pc)

1 millimeter equals 3.240779289×10⁻²⁰ parsecs (rounded).

1 millimeter = 3.240779289×10⁻²⁰ parsecs

How to convert millimeters to parsecs

To convert millimeters to parsecs, multiply the number of millimeters by 3.240779289×10⁻²⁰. The factor is rounded to 10 significant digits. To go the other way, multiply parsecs by 3.085677581×10¹⁹ (rounded).

parsecs = millimeters × 3.240779289×10⁻²⁰

Example: 10 millimeters = 3.240779289×10⁻¹⁹ parsecs.

About these units

Millimeter (mm)

Metric (SI)Current unit

One thousandth of a meter. Used in engineering, manufacturing and rainfall measurement.

Carl Friedrich Gauss put the millimeter at the base of his 1832 proposal for absolute units, pairing it with the milligram and the second, although the centimeter-based CGS system later won out among scientists. The name combines the metric prefix milli-, from the Latin for one thousand, with the meter. Since 1983 a millimeter has been tied to the speed of light: it is the distance light covers in 1/299,792,458,000 of a second.

Millimeters are the language of fine mechanical work. Standard rulers are divided into them, digital calipers commonly read to 0.01 mm, and mechanical pencil leads come in 0.5 and 0.7 mm. Copy paper is about 0.1 mm thick, and a thin hair, at 0.02 to 0.04 mm across, is close to the smallest thing the naked eye can see. A wave with a frequency of 300 GHz has a wavelength of 1 mm. An inch is exactly 25.4 mm. One trap for readers in the United States is that mil there traditionally means a thousandth of an inch, not a millimeter.

1 millimeter = 0.001 meters (exactly).

Sources: Wikipedia: Millimetre; Wikipedia: Centimetre-gram-second system of units; NIST Guide to the SI, Appendix B.8: conversion factors

Parsec (pc)

AstronomicalCurrent unit

About 3.26 light-years, defined as 648,000/π astronomical units. The standard unit for distances to stars.

British astronomer Herbert Hall Turner coined the word in 1913 as a contraction of the distance at which a parallax equals one arcsecond. Rivals were Frank Dyson's astron and Carl Charlier's siriometer. The idea rests on stellar parallax, first measured successfully by Friedrich Bessel in 1838 for 61 Cygni, which he put near 3.5 parsecs. With the angle in arcseconds, the distance in parsecs is simply its reciprocal.

Since 2015 the IAU has defined the parsec as exactly 648,000 divided by pi astronomical units, which with the 2012 exact au gives about 30,856,775,814,913,673 meters, or 3.0857 times ten to the sixteenth power. That is roughly 3.26 light-years. Proxima Centauri lies about 1.3 parsecs away. Professional astronomers still prefer the parsec to the light-year, and ESA's Gaia satellite, launched in 2013, measures parallaxes to microarcsecond precision.

1 parsec = 3.085677581×10¹⁶ meters (approximately).

Sources: Wikipedia: Parsec; NIST SP 811 Appendix B.8: factors for units outside the SI

Related conversions

See all length units.