Question

What's the greatest? 1 atm, 1 Torr, 1 mmHg, 1 kPa

Answer 1

Hint: A unit of measurement is a specified magnitude of a quantity that is used as a standard for measuring the same sort of quantity. It is established and approved by agreement or by legislation. A multiple of the unit of measurement can be used to express any other quantity of that type. Units are standards for measuring physical quantities that need explicit definitions in physics and metrology.

Complete answer:
The amount of force exerted at right angles to an object's surface per unit area is known as pressure. "p" or P is the sign for it. The force applied perpendicular to the surface of an item per unit area across which that force is spread is known as pressure (symbol: p or P). Differential pressure is measured in units with a "d" attached; it's important for determining how well a valve seals or if it will open or close.
The height of the mercury column in a barometer is used to measure gas pressure. The millimetre of mercury is one unit of gas pressure (mmHg). The torr, named after the creator of the barometer, Evangelista Torricelli, is an analogous unit to the mmHg. The standard unit of pressure is the pascal (Pa). Because a pascal is a relatively small measure of pressure, the kilopascal is a more relevant unit for daily gas pressures (kPa). 1000 pascals equals a kilopascal. The atmosphere is another widely used unit of pressure (atm). 1 atm of pressure is equal to 760 mmHg and 101.3 kPa and is the standard atmospheric pressure.
Pounds per square inch is another way to express atmospheric pressure (psi). At sea level, the air pressure is 14.7 psi.
\[\text{1atm = 760mmHg = 760torr = 101}\text{.3KPa = 14}\text{.7psi}\]
\[\text{1 Torr = 0}\text{.1333kPa, 1 kPa = 7}\text{.50 Torr}\text{.}\]
It's crucial to be able to convert between different pressure units. We'll utilise the comparable standard pressures shown above to do so.
Hence 1 atm is the greatest.

Note:
The pressure within Earth's atmosphere is known as atmospheric pressure. The standard atmosphere is specified as 101,325 Pa (1,013.25 hPa; 1,013.25 mbar), which is comparable to 760 mm Hg, 29.9212 inches Hg, or 14.696 pounds per square inch. The atm unit roughly corresponds to the Earth's mean sea-level atmospheric pressure; that is, the atmospheric pressure at sea level is about 1 atm.