Introduction to Units & Measurement

Units of Measurement

The table below shows the Units of Measurement also called SI Units.

Derived SI units are constructed from the appropriate base units such the SI unit of speed is meters per second, m/s.

Base units are converted into units that are more common or convenient as illustrated in the table below.

Prefixes Used in the Metric System and with SI Units
Prefix	Abreviation	Meaning	Example
Peta	P	10¹⁵	1 petabyte (PW) = 1 × 10¹⁵ bytes
Tera	T	10¹²	1 terawatt (TW) = 1 × 10¹² watts
Giga	G	10⁹	1 gigajoule (GJ) = 1 × 10⁹ joules
Mega	M	10⁶	1 megabyte (MB) = 1 × 10⁶ bytes
Kilo	k	10³	1 kilogram (kg) = 1 × 10³ grams
Deci	d	10^{− 1}	1 decimeter(dm) = 1 × 10^{− 1} meter
Centi	c	10^{− 2}	1 centimeter(cm) = 1 × 10^{− 2} meter
Melli	m	10^{− 3}	1 milliwatt (mW) = 1 × 10^{− 3} watt
Micro	μ	10^{− 6}	1 microjoule(μJ) = 1 × 10^{− 6} joule
Nano	n	10^{− 9}	1 nanosecond(ns) = 1 × 10^{− 9} second
Pico	p	10^{− 12}	1 picowatt(pW) = 1 × 10^{− 12} watt
Femto	f	10^{− 15}	1 femtosecond(fs) = 1 × 10^{− 15} second
Atto	a	10^{− 18}	1 attowatt(aW) = 1 × 10^{− 18} watt
Zepto	d	10^{− 21}	1 zeptojoule(zJ) = 1 × 10^{− 21} joule

Celsius scale: based on the properties of water.
Kelvin scale: the “absolute” temperature, which is the SI unit of temperature.
The Kelvin unit has the same size as the Celsius unit, but the two scales have different zero points.
0 K is the lowest possible temperature ("absolute zero").
This the point at which all thermal energy would have been drained from an object; so the temperature cannot get any lower.
0 K = − 273.15 °C, so K = °C + 273.15

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