Online Unit Converters

Alternative Unit Systems of Measurement

While the International System of Units (SI), U.K. Imperial system, and U.S. customary system dominate modern measurement practices, several other unit systems have played crucial roles in science and industry. Each of these alternative systems has its unique history and applications that make them relevant in specific contexts. Let's have a look at some of them:

Metric Systems

CGS System (Centimeter-Gram-Second)

  • Definition: The CGS system is a metric-based system using centimeters for length, grams for mass, and seconds for time.
  • Status: Primarily historic but still used in some scientific fields like electromagnetism.
  • Base Units: Centimeter (cm), Gram (g), Second (s).
  • Specialized Use: Commonly used in physics for calculations involving small-scale measurements.

MKS System (Meter-Kilogram-Second)

  • Definition: The MKS system is a predecessor to the International System of Units (SI), using meters for length, kilograms for mass, and seconds for time.
  • Status: Historic; replaced by SI but foundational to modern measurement.
  • Base Units: Meter (m), Kilogram (kg), Second (s).
  • Specialized Use: Basis for modern scientific measurements.

MTS System (Meter-Tonne-Second)

  • Definition: A metric system using meters for length, tonnes for mass, and seconds for time.
  • Status: Historic; rarely used today.
  • Base Units: Meter (m), Tonne (t), Second (s).
  • Specialized Use: Designed for engineering applications involving large masses.

International Table (IT) System

  • Definition: A system used for defining weights and measures, particularly in the context of the metric system.
  • Status: Used internationally for standardizing weights and measures.
  • Base Units: Kilogram (kg), Meter (m), Second (s), etc.
  • Specialized Use: International trade and scientific research for uniformity.

Imperial Systems

FPS System (Foot-Pound-Second)

  • Definition: An imperial system using feet for length, pounds for force or weight, and seconds for time.
  • Status: Still in limited use in the United States and some engineering fields.
  • Base Units: Foot (ft), Pound-force (lbf), Second (s).
  • Specialized Use: Engineering and mechanics in the US.

Specific Systems

Thermodynamic System

  • Definition: A system based on thermodynamic principles, particularly for temperature measurements.
  • Status: Used in scientific applications for precise temperature measurements.
  • Base Unit: Kelvin (K).
  • Specialized Use: Scientific research involving precise temperature control.

Sexagesimal System

  • Definition: An ancient Mesopotamian system based on the number 60, still used today for measuring time, angles and geographic coordinates.
  • Status: Still in use for timekeeping and angular measurements.
  • Main Units: Degrees, Minutes, Seconds.
  • Specialized Use: Timekeeping and angular measurements in navigation and astronomy.

Apothecaries' System

  • Definition: A historic system of weights and measures used by pharmacists.
  • Status: Historic; replaced by the metric system in most countries.
  • Main Units: Grain, Scruple, Dram, Ounce.
  • Specialized Use: Medicine and pharmacy in earlier centuries.

Avoirdupois System

  • Definition: A weight-based system commonly used in commerce in the US and UK.
  • Status: Still in use for everyday trade in non-metric countries like the US.
  • Main Units: Pound (lb), Ounce (oz).
  • Specialized Use: General trade and commerce.

Troy System

  • Definition: A system of weights used primarily for precious metals.
  • Status: Still in use for precious metals like gold and silver.
  • Main Units: Troy Ounce, Troy Pound.
  • Specialized Use: Precious metals trade.

English Engineering Units (US)

  • Definition: A system combining elements of imperial and US customary units for engineering applications.
  • Status: Still used in some engineering fields in the US.
  • Main Units: Foot (ft), Pound-force (lbf), Second (s), Degree Fahrenheit (°F).
  • Specialized Use: Engineering and construction in the US.

Natural Systems

Atomic Units

  • Definition: A system based on fundamental physical constants like the electron mass and charge.
  • Status: Used in atomic physics and quantum mechanics.
  • Base Units: Electron mass, Electron charge, Reduced Planck constant.
  • Specialized Use: Atomic and molecular physics.

Planck Units

  • Definition: A system derived from fundamental physical constants like the speed of light and Planck constant.
  • Status: Used in theoretical physics, particularly in cosmology and quantum gravity.
  • Base Units: Planck length, Planck time, Planck mass.
  • Specialized Use: Theoretical physics and cosmology.

Ancient unit systems

Ancient systems of measurement were developed by early civilizations to standardize trade, construction, and administration. These systems varied widely but often included units for length, weight, area, and volume. Below is an overview of some notable ancient measurement systems:

  • Babylonian System: Used in ancient Mesopotamia for trade and commerce. Key units included the kush (cubit, about 0.5 m) for length, the mana (500 g) for weight, and the sila (1 liter) for capacity.
  • Egyptian System: Used in ancient Egypt for building and trade. Important units included the royal cubit (about 52.4 cm) for length, the deben (91 g) for weight, and the hekat (4.8 liters) for volume.
  • Greek System: Used in ancient Greece for various measurements. Notable units included the stadion (185 m) for distance, the talent (26 kg) for weight, and the metrētēs (39.4 liters) for volume.
  • Roman System: Used in ancient Rome for building and trade. Key units were the pes (foot, about 29.6 cm) for length, the libra (327 g) for weight, and the amphora (26 liters) for volume.
  • Biblical System: Mentioned in the Bible for trade and commerce. Units like the cubit (44 - 52 cm), ephah (22 liters), and shekel (11 g) were commonly used.

Key features across ancient unit systems:

  • Many systems were tied to human anatomy (e.g., cubits based on arm length).
  • They were often influenced by natural phenomena like river floods (e.g., Nile measurements in Egypt).
  • Standardization efforts, such as Naram-Sin's reforms in Mesopotamia or Athens' central depository of standards, highlight their importance in administration and trade.

These ancient systems laid the groundwork for modern measurement practices while reflecting the ingenuity of early civilizations in addressing practical needs.

Local unit systems

Local systems of measurement have been historically developed across the world to suit regional needs and practices.

  • Chinese System: Featured units like the chi (length, ~33 cm), liang (weight, ~37.5 g), and sheng (volume, ~1 liter).
  • Japanese System: Included the shaku (length, ~30.3 cm), kan (weight, ~3.75 kg), and koku (volume, ~180 liters).
  • Russian System: Used the arshin (length, ~71 cm), pood (weight, ~16.38 kg), and chetvert (volume, ~26 liters).
  • Spanish System: Units like the vara (length, ~0.835 m) and arroba (weight, ~11.5 kg) were prominent.

These systems reflect cultural adaptations to trade, agriculture, and construction before the widespread adoption of standardized metric systems.