Pressure Converter
Convert pascals, psi, bar, atm, torr, millibar, etc.
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*Diagram shows values relative to the selected base unit (Pascal).
Unit Information
What are Pascals (Pa)?
The Pascal (symbol: Pa) is the SI derived unit of pressure, named after the French mathematician and physicist Blaise Pascal. One Pascal is defined as one newton of force per square meter (N/m²). Due to its small magnitude, multiples like kilopascals (kPa) and hectopascals (hPa) are often used.
What are Pounds per Square Inch (psi)?
Pounds per square inch (symbol: psi or lb/in²) is a unit of pressure in the imperial and US customary systems. It represents the pressure resulting from a force of one pound-force applied to an area of one square inch. It is commonly used in the United States for measuring tire pressure and hydraulic system pressures.
What is a Bar?
A bar is a metric unit of pressure, defined as exactly 100,000 Pascals. It is not an SI unit, but it is widely used in industry and meteorology because it is approximately equal to standard atmospheric pressure.
What is an Atmosphere (atm)?
A standard atmosphere (atm) is a unit of pressure defined as 101,325 Pa. It is intended to represent the mean atmospheric pressure at mean sea level.
What is a Torr (mmHg)?
A Torr, named after Evangelista Torricelli, is a unit of pressure based on an absolute scale, defined as exactly 1/760 of a standard atmosphere. It is approximately equal to the pressure exerted by a one-millimeter column of mercury (mmHg) and is often used for measuring vacuums.
What are Millibars (mbar) and Hectopascals (hPa)?
A millibar is one-thousandth of a bar (1 mbar = 100 Pa). A hectopascal is one hundred Pascals (1 hPa = 100 Pa). These two units are numerically identical and are the standard units used in meteorology for reporting atmospheric pressure.
Formulas
1 psi ≈ 6894.76 Pa
To convert pounds per square inch (psi) to Pascals (Pa), multiply by approximately 6894.76.
1 bar = 100,000 Pa
A bar is defined as 100 kilopascals.
1 atm = 101,325 Pa
A standard atmosphere is defined as 101,325 Pascals.
1 atm ≈ 14.696 psi
One standard atmosphere is approximately 14.7 psi.
1 bar ≈ 14.504 psi
One bar is approximately 14.5 psi.
1 atm = 760 Torr
A standard atmosphere is defined as 760 Torr.
Key Reference Points
- Typical car tire pressure: ~30-35 psi (200-240 kPa or 2.0-2.4 bar).
- Standard atmospheric pressure at sea level: ~101.3 kPa (14.7 psi, 1 atm).
- Pressure inside a bicycle road tire: ~80-120 psi (550-830 kPa or 5.5-8.3 bar).
- Blood pressure is measured in millimeters of mercury (mmHg), where 1 mmHg ≈ 1 Torr ≈ 133.322 Pa.
- A typical home water pressure is around 40-60 psi.
- Pressure at the bottom of the Mariana Trench: over 108 MPa or 15,750 psi.
- Pressure at the center of the Earth: approximately 360 GigaPascals (GPa).
- A perfect vacuum is 0 Pascals.
- Pressure on the surface of Mars: about 600 Pa (0.6% of Earth's).
- Pressure inside a pressure cooker: about 15 psi above atmospheric pressure.
Did You Know?
Standard atmospheric pressure (atm) at sea level is defined as 101,325 Pascals. This is approximately equal to 14.696 psi, 1.01325 bar, or 760 Torr (mmHg). Weather systems cause atmospheric pressure to vary, which is why barometers use units like millibars or hectopascals.
The boiling point of a liquid depends on the surrounding pressure. At lower pressures (like at high altitudes), water boils at a lower temperature than at sea level.
A vacuum is a space devoid of matter, or where the pressure is significantly lower than atmospheric pressure. Vacuums are crucial in various technologies, from light bulbs to particle accelerators, and are often measured in Pascals or Torr.
The barometer was invented by Evangelista Torricelli in 1643. His experiment with a tube of mercury demonstrated that the atmosphere had weight and exerted pressure, and that this pressure changed with weather.
The atmospheric pressure on the surface of Venus is about 92 times that of Earth's, equivalent to the pressure found about 900 meters (3,000 ft) underwater on Earth. This crushing pressure is one reason landing probes on Venus is so challenging.
A person's weight exerts a force, but pressure depends on area. A person wearing stiletto heels concentrates their entire weight onto a very small area, creating an immense pressure on the ground—far greater than that exerted by an elephant's foot.
Blood pressure is typically measured in millimeters of mercury (mmHg), which is nearly equivalent to the Torr unit. The two numbers (e.g., 120/80) represent systolic (maximum) and diastolic (minimum) pressure in the arteries.
Pascal's principle states that a pressure change at any point in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere. This is the fundamental principle behind hydraulic systems.
Sound travels as pressure waves. The small, rapid fluctuations in air pressure are what our eardrums detect and our brains interpret as sound. The amplitude of these pressure waves determines the loudness of the sound.
The pressure at the bottom of the Mariana Trench, the deepest part of the ocean, is over 1,000 times standard atmospheric pressure, exceeding 100 megapascals (MPa) or 15,000 psi.
The 'bar' is a metric unit of pressure that is not part of the SI system, but is widely used. It was defined to be approximately equal to one standard atmosphere. 1 bar is exactly 100,000 Pascals.
The critical pressure of a substance is the pressure above which a distinct liquid and gas phase do not exist. Above this pressure, the substance is in a state called a supercritical fluid.
In a mixture of gases, the partial pressure of each gas is the hypothetical pressure of that gas if it alone occupied the entire volume of the mixture at the same temperature. Dalton's Law states that the total pressure is the sum of the partial pressures.
A manometer is a simple instrument for measuring pressure, consisting of a U-shaped tube containing a liquid. The difference in the height of the liquid in the two arms indicates the pressure difference between the two ends.
Vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. It's an indication of a liquid's evaporation rate.
The technical atmosphere (at) is a non-SI unit of pressure equal to one kilogram-force per square centimeter. It is very close to the standard atmosphere (atm) but is defined differently.
This principle states that for an inviscid flow of a fluid, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy. It's why an airplane's wing generates lift.
Autoclaves, used for sterilization in medical and laboratory settings, work by increasing the pressure inside a sealed chamber. This allows water to be heated above its normal boiling point, ensuring the destruction of all microorganisms.