Converting Units Reference Page
Is Furlongs Per Fortnight a Thing?

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Purpose of Is Furlongs Per Fortnight a Thing?

Engineers often need to work with multiple unit systems. In the United States, many industries still use American Engineering units, also called U.S. Customary units or, less precisely, Imperial units. Even in countries that primarily use SI units, engineers still convert among grams and kilograms, millimeters and meters, and many other related quantities. In everyday language, people also often speak of “weight” when they actually mean mass.

Engineers must be able to convert units accurately and confidently. This video explains the most common type of unit conversion: converting measured quantities using dimensional equations or unit-conversion factors.

A second video, How Keen Is Your Rank? JTF, TFS, Info Page, explains how to perform temperature and temperature-interval conversions, many of which cannot be handled by the methods in this video.

A third video, The Most Annoying Equation Conversion, Video, Info Page, explains how to convert an equation, rather than a measurement or temperature, from one set of units to another.

Is Furlongs Per Fortnight a Thing?

This video explains dimensional equations and unit-conversion factors and then works through several examples. It is suitable both for viewers who are just learning unit conversions and for those who want a refresher.

Visuals

Some Common Conversions

Exact

\(\frac{25.4\ \mathrm{mm}}{1\ \mathrm{inch}}\),   \(\frac{101325\ \mathrm{Pa}}{1\ \mathrm{atm}}\),   \(\frac{4.184\ \mathrm{J}}{1\ \mathrm{cal_{th}}}\),   \(\frac{9\ \mathrm{^\circ R}}{5\ \mathrm{K}}\),   \(\frac{4.184\ \mathrm{J/(kg\cdot K)}}{1\ \mathrm{Btu_{th}/(lb_m \cdot ^\circ R)}}\).

Close to Exact (worth memorizing to 3 or 4 significant figures)

\(\frac{0.4535924\ \mathrm{kg}}{1\ \mathrm{lb_m}}\),   \(\frac{4.448222\ \mathrm{N}}{1\ \mathrm{lb_f}}\),   \(\frac{0.9463529\ \mathrm{L}}{1\ \mathrm{qt}}\).

Mass to Weight and Vice Versa

American Engineering: \(\frac{1\ \mathrm{lb_f\ s^2}}{32.174\ \mathrm{lb_m\ ft}}\)
SI: \(\frac{1\ \mathrm{N\ s^2}}{\mathrm{kg\ m}}\)

Approximate

\(\frac{2.2\ \mathrm{lb_m}}{1\ \mathrm{kg}}\),   \(\frac{1\ \mathrm{Btu/s}}{1\ \mathrm{kW}}\).

Definitions

Pound Mass, \(\mathrm{lb_m}\)
A unit of mass in the American Engineering system. One pound mass experiences a force of one pound force in the standard gravitational field.
Pound Force, \(\mathrm{lb_f}\)
The force exerted by one pound mass in the standard gravitational field of \(32.174\ \mathrm{ft/s^2}\).
Kilogram Mass, \(\mathrm{kg}\)
The SI base unit of mass.
Kilogram Force, \(\mathrm{kg_f}\)
The force exerted by a mass of one kilogram in the standard gravitational field of \(9.80665\ \mathrm{m/s^2}\). It is equal to \(9.80665\ \mathrm{N}\).
Celsius
A commonly used temperature scale in SI-based practice, named after Anders Celsius.