US Survey Feet to Millimeters (ft (US) to mm)

1 US survey foot equals 304.8006096 millimeters (rounded).

1 US survey foot = 304.8006096 millimeters

How to convert US survey feet to millimeters

To convert US survey feet to millimeters, multiply the number of US survey feet by 304.8006096. The factor is rounded to 10 significant digits. To go the other way, multiply millimeters by 0.003280833333 (rounded).

millimeters = US survey feet × 304.8006096

Example: 10 US survey feet = 3,048.006096 millimeters.

About these units

US Survey Foot (ft (US))

US land surveyHistorical unit (no longer in standard use)

Exactly 1200/3937 meters, about 2 parts per million longer than the international foot. Retired in the US at the end of 2022 but still found in older land records.

Two feet coexisted in the United States for sixty-three years. The Mendenhall Order of 1893 tied American units to the metre at 39.37 inches to the metre, which makes the survey foot exactly 1200/3937 m, about 0.3048006 m. In 1959 the international foot was set at exactly 0.3048 m for industry and trade, but the older foot was kept for geodetic work until control networks could be readjusted. That readjustment was finished in 1986, yet the survey foot stayed in use.

The two differ by about 2 parts per million. That is trivial for a house lot but adds up in the State Plane Coordinate System, where coordinates can lie hundreds of thousands of feet from their origin. NIST and the National Geodetic Survey announced that the survey foot should not be used after December 31, 2022, with the international foot replacing it, leaving it for historic and legacy data. Before that, state laws varied: about 40 of 56 jurisdictions based surveying on the survey foot, six on the international foot, and ten did not specify.

1 US survey foot = 0.3048006096 meters (approximately).

Sources: NIST: U.S. survey foot; Wikipedia: Foot (unit)

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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