Roman Cubits to Millimeters (cubitum to mm)

1 Roman cubit equals 444 millimeters exactly.

1 Roman cubit = 444 millimeters

How to convert Roman cubits to millimeters

To convert Roman cubits to millimeters, multiply the number of Roman cubits by 444. This factor is exact. To go the other way, multiply millimeters by 0.002252252252 (rounded).

millimeters = Roman cubits × 444

Example: 10 Roman cubits = 4,440 millimeters.

Approximate value. Standards for the Roman cubit 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 Cubit (cubitum)

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

One and a half Roman feet, about 44.4 cm.

Cubitum was the Latin word for elbow, and it came from a verb meaning to lie down or recline, the root of the English cubit. Roman writers such as Vitruvius defined it as one and a half Roman feet, or six palm widths, which gives about 444 mm. That is the figure used here. It was meant to span roughly the length of the forearm from the elbow to the fingertips.

Compared with other ancient cubits it was short. The Egyptian royal cubit survives on rods measuring about 523 to 529 mm, and Wikipedia says ancient cubits generally ranged from about 44.4 to 52.9 cm, so the Roman one sits at the bottom of that range. Romans also used a separate, longer ulna of about 120 cm. In a modern setting the Roman cubit is a little over 17 inches.

1 Roman cubit = 0.444 meters (approximately).

Sources: Wikipedia: Cubit; Wikipedia: Ancient Roman units of measurement

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

Related conversions

See all length units.