The International System of Units is known by the international abbreviation SI in all languages. The SI comprises a coherent system of units of measurement starting with seven base units, which are the second (symbol s, the unit of time), metre (m, length), kilogram (kg, mass), ampere (A, electric current), kelvin (K, thermodynamic temperature), mole (mol, amount of substance), and candela (cd, luminous intensity).

ABBREVIATIONS OF UNITS OF MEASUREMENT

Abbreviations for most units of measurements use small letters and periods.

Temperature abbreviations use capitals because they come from proper nouns.

CONVERSION FACTORS

Distances

Temperature

The Kelvin scale is an absolute thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics. The Kelvin is the base unit of temperature in the International System of Units.

Pressure

Pressure is the amount of force applied perpendicular to the surface of an object per unit area. The SI unit for pressure is the pascal (Pa), equal to one newton per square metre. In the English system, pressure is usually expressed in pounds per square inch (psi).The torr (symbol: Torr) is a unit of pressure based on an absolute scale, defined as exactly 1/760 of a standard atmosphere.
1 bar = 1 atm = 1 kg/cm² = 100 kPa = 14.5 psi = 750 Torr

UNITS OF MEASUREMENTS FOR INJECTION SUPPLIES

Simply gauge, G or GA generally refers to Birmingham gauge or British gauge Calibre, where an increasing gauge corresponds to a smaller diameter needle.
The Birmingham gauge is a wire gauge system, and is also used to specify the outside diameter of hypodermic needles, catheters, cannulae and suture wires. Birmingham gauge is often simply termed Gauge, with the abbreviation G. Smaller gauge numbers indicate larger outer diameters. Inner diameter depends on both gauge and wall thickness.
The gauge starts at the lowest gauge number 5 corresponding to the largest size of 12.7mm. The highest gauge number 36 corresponds to the smallest size of 0.102mm. Size steps between gauges range from 0.025 mm between high gauge numbers to 1.17 mm between the two lowest gauge numbers and do not correspond to a particular mathematical pattern, although for the most part the steps get smaller with increasing gauge number.
Note: The gauge/mm correspondence may vary, due to figures being rounded off in conversion from inches to mm

Sizes of hypodermic needles

UNITS OF MEASUREMENT FOR CATHETER SUPPLIES

The French scale or French gauge system is commonly used to measure the outer diameter of a catheter. It is most often abbreviated as Fr, but can often be seen abbreviated as Fg, FR or F. It may also be abbreviated as CH or Ch (for Charrière, its inventor).

• A round catheter of 1 French has an external diameter of 1⁄3 mm,
• D (mm) = Fr / 3 or Fr = D (mm) x 3
• An increasing French size corresponds to a larger external diameter.