Roman Leagues to Millimeters (leuga to mm)

1 Roman league equals 2,220,000 millimeters exactly.

1 Roman league = 2,220,000 millimeters

How to convert Roman leagues to millimeters

To convert Roman leagues to millimeters, multiply the number of Roman leagues by 2,220,000. This factor is exact. To go the other way, multiply millimeters by 4.504504505×10⁻⁷ (rounded).

millimeters = Roman leagues × 2,220,000

Example: 10 Roman leagues = 22,200,000 millimeters.

Approximate value. Standards for the Roman league varied by place and period, so this converter uses the most commonly cited value. Treat results as estimates, not exact figures.

About these units

Roman League (leuga)

Ancient RomanHistorical unit (no longer in standard use)Approximate value

One and a half Roman miles (7,500 Roman feet), about 2.22 km. Used in Gaul and later across the empire for longer distances.

Gaul, not Rome, gave this unit its name. The Latin leuga or leuca came from a Celtic measure of the Gauls that the Romans adopted, and it is the ancestor of the later European league. It may originally have approximated the distance a person could walk in an hour, though that is a suggestion rather than a documented definition.

In Roman terms it was fixed at one and a half Roman miles, or 7,500 Roman feet, which comes to about 2.22 km. Under Septimius Severus this Gallo-Roman league replaced the mile as the official road distance in the Gallic and Germanic provinces. Even so, its practical length varied by region and period, so 2,220 m is a convention based on the 296 mm foot rather than a measured constant.

Later leagues strayed far from the Roman original. Medieval and later values ran from about 2.2 km up to nearly 8 km, with the English league taken as three miles, the Spanish common league near 5.57 km, and a French metric lieue set at exactly 4 km in 1812. No country officially uses it now, though Jules Verne's famous title keeps the word familiar.

1 Roman league = 2,220 meters (approximately).

Sources: Wikipedia: League (unit); Wikipedia: Roman units of measurement; Wikipedia: Roman mile

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

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