Pouces to Millimeters (pouce to mm)

1 pouce equals 27.06994875 millimeters (rounded).

1 pouce = 27.06994875 millimeters

How to convert pouces to millimeters

To convert pouces to millimeters, multiply the number of pouces by 27.06994875. The factor is rounded to 10 significant digits. To go the other way, multiply millimeters by 0.03694133333 (rounded).

millimeters = pouces × 27.06994875

Example: 10 pouces = 270.6994875 millimeters.

About these units

Pouce (pouce)

French (Ancien Régime)Historical unit (no longer in standard use)

The old French inch, about 2.707 cm; slightly longer than the English inch.

Pouce means thumb in French, the same body-part logic found in many inch-like units. In the royal system it was one twelfth of the pied du roi, which gives about 27.07 millimetres, or roughly 1.066 English inches. Each pouce was in turn divided into twelve lignes.

Craftsmen, surveyors and builders across France quoted lengths in pieds, pouces and lignes until the metric reforms of the 1790s, and the pouce was the natural unit for small dimensions. Because the French inch was slightly longer than the English one, converting between the two traditions always needs the exact ratio and not a rough equivalence.

The pouce shared the history of the foot it came from. Its size depended on the royal standard, which was an iron toise bar kept in Paris, and that bar was replaced after it was found deformed in 1668. Under the metric law of 1799 it was fixed in relation to the metre, and the same ratio is quoted today.

1 pouce = 0.02706994875 meters (approximately).

Sources: Wikipedia: Pied du roi; Wikipedia: Traditional French units of measurement; Wikipedia: Toise

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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