British Imperial System
A principal system of units.
English units forms the basic for the Imperial system formerly used in the Commonwealth countries and the Customary system used in the US.
The basic difference between dimensional systems are not the units employed but the primary dimensions.
- The SI-system use mass, length and time as primary quantities (mechanics). Other units quantities are secondary. The SI-system is a MLT (mass-length-time) system
- The English system use force, mass, length and time as primary quantities. Other units are secondary. The British Imperial System is a FMLT (force-mass-length-time) system
Note that the use of four, three, two or even one(!) primary quantities is a human choice and not necessary basic nature.
Imperial Primary Quantities
Imperial primary quantities are expressed in the table below:
| Primary Quantity | Dimensions | Common Units |
|---|---|---|
| Force | F | pound-force |
| Mass | M | ounce, pound, slug, ton |
| Length | L | inch, foot, yard rod, chain, furlong, mile |
| Time | T | second, minute hour, day |
Imperial Secondary Quantities
Some common imperial secondary quantities are expressed in the table below
| Primary Quantity | Dimensions | Common Units |
|---|---|---|
| Acceleration | L / T2 | foot per second squared |
| Area | L2 | square foot, square yard acre, square mile |
| Density | M / L3 | pounds per cubic foot |
| Frequency | 1/T | cycle per second |
| Impulse | F T | pound-force second |
| Momentum | ML / T | pound foot per second |
| Power | LF / T | foot pound-force per second horsepower |
| Pressure | F / L2 | pound-force per square inch |
| Velocity | L / T | foot per second mile per hour, knot |
| Volume | L3 | pint, quart, gallon cubic foot, cubic yard |
| Work | L F | foot pound-force |
Related Topics
-
Basics
Basic engineering data. SI-system, unit converters, physical constants, drawing scales and more.
Related Documents
-
BSi - Pipe, Tube and Fittings Standards and Specifications
British standards and specifications for pipe, tube and fittings. -
Decimal System Prefixes
Prefix names used for multiples and submultiples units. -
Radians vs. Degrees
Radian is the SI unit of angle. Convert between degrees and radians. Calculate angular velocity. -
SI System
An introduction to the SI metric system. -
Symbols Used to Denote a Chemical Reactions and Process or Condition
Explanation of symbols used as subscripts or superscripts to tell more about the type of chemical reaction, process or condition. -
Toluene Liquid - Thermal Properties vs. Temperature
Density, specific heat, thermal conductivity and more. -
Unit Converter with commonly used Units
Common converting units for Acceleration, Area, Density, Energy, Energy per unit mass, Force, Heat flow rate, Heat flux, Heat generation per unit volume and many more. -
USCS - United States Customary System Units
An overview of the United States Customary System Units - Imperial Units.
