Roman Stadia to Millimeters (stadium to mm)

1 Roman stadium equals 185,000 millimeters exactly.

1 Roman stadium = 185,000 millimeters

How to convert Roman stadia to millimeters

To convert Roman stadia to millimeters, multiply the number of Roman stadia by 185,000. This factor is exact. To go the other way, multiply millimeters by 0.000005405405405 (rounded).

millimeters = Roman stadia × 185,000

Example: 10 Roman stadia = 1,850,000 millimeters.

Approximate value. Standards for the Roman stadium 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 Stadium (stadium)

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

125 paces or 625 Roman feet, about 185 m. One eighth of a Roman mile.

Borrowed from the Greek stadion, the Latin stadium named a racecourse length that Romans also used as a route unit. It was defined as 125 paces, or 625 Roman feet, and eight of them made one Roman mile. That puts it at about 185 m, the figure used here, and it is the ancestor of the medieval furlong, itself an eighth of a mile.

The Greek original is far less settled. By Herodotus a stadion was 600 Greek feet, but the foot varied across the Greek world, so historians propose anything from roughly 150 m to 210 m. Itinerary, Olympic, Attic and Persian versions have each been argued for, with figures near 157 m, 192 m, 185 m and 196 m respectively. The Roman value lines up with the Attic estimate rather than the others.

Because the Roman unit is defined through a foot of about 296 mm, any change to that foot changes the stadium too. Surveyors and geographers used the unit for road distances and for scaling the world, and today it survives mostly in the word stadium for a sports venue.

1 Roman stadium = 185 meters (approximately).

Sources: Wikipedia: Roman units of measurement; Wikipedia: Stadion (unit); 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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