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Pressure Converter

Convert between bar, psi, atm, pascal, and more

Free online pressure converter. Convert between bar, PSI, standard atmosphere, pascal, kilopascal, megapascal, mmHg, inHg, and torr. Fast, accurate pressure unit conversion.

How to convert pressure units?

Converting between pressure units is straightforward with our tool. Here's exactly how to get precise results:

  • Enter your pressure value in the input field. You can type whole numbers like 100, decimals like 1.01325, or scientific notation like 1e5.
  • Select your source unit from the first dropdown. Choose from bar, psi (pounds per square inch), atm (standard atmosphere), Pa (pascal), kPa (kilopascal), MPa (megapascal), mmHg (millimeters of mercury), inHg (inches of mercury), or torr.
  • Choose your target unit from the second dropdown. The result appears instantly — for example, entering 1 bar shows 14.5038 psi, 0.9869 atm, or 100,000 Pa.
  • Use the Swap button to reverse the direction without re-entering data. This is useful when checking equivalent values like 101.325 kPa (standard atmospheric pressure) in different units.
  • Copy any result using the copy icon next to the result field. The formula is displayed below the result for reference.

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Understanding pressure units and when to use each

Pressure measures force per unit area and appears in countless contexts from weather forecasting to tire inflation to deep-sea diving. The bar (1 bar ≈ atmospheric pressure at sea level) is commonly used in meteorology and engineering. PSI (pounds per square inch) is the standard in the United States for tire pressure, hydraulic systems, and scuba tanks. The standard atmosphere (atm) was originally defined as average sea-level pressure and is used in chemistry for gas laws. The pascal (Pa) is the SI unit — one newton per square meter — but because it's a very small unit, kilopascals (kPa) and megapascals (MPa) are more practical. Millimeters of mercury (mmHg) and torr are essentially identical and are used in medicine for blood pressure and in vacuum measurements. Inches of mercury (inHg) is common in aviation weather reports in the US.

Real-world pressure references

  • Standard atmospheric pressure at sea level: 1 atm = 1.01325 bar = 14.6959 psi = 101.325 kPa = 760 mmHg = 29.92 inHg
  • Car tire pressure: typically 2.0-2.5 bar (30-36 psi)
  • Blood pressure: normal systolic reading is around 120 mmHg (16 kPa)
  • Scuba tank: filled to about 200 bar (3000 psi)
  • Vacuum cleaner: creates suction of about 0.2 bar (20 kPa) below atmospheric
  • Pressure cooker: operates at about 1.8 bar (26 psi) absolute pressure
  • Deep-sea pressure: increases by roughly 1 bar every 10 meters of depth

Frequently Asked Questions (FAQs)

What is the difference between bar and PSI?

Bar and PSI are both pressure units. 1 bar equals approximately 14.5038 psi. Bar is based on the metric system and is widely used in Europe and for scientific purposes. PSI (pounds per square inch) is the standard in the United States and is commonly used for tire pressure, hydraulic systems, and industrial applications. To convert bar to psi, multiply by 14.5038. To convert psi to bar, divide by 14.5038.

What is standard atmospheric pressure?

Standard atmospheric pressure at sea level is defined as 1 atm = 1.01325 bar = 101.325 kPa = 14.6959 psi = 760 mmHg = 29.92 inHg. This is the average pressure exerted by Earth's atmosphere at sea level. It decreases with altitude — at 5,000 meters, atmospheric pressure is about 0.5 bar.

Is mmHg the same as torr?

Yes, for practical purposes, mmHg and torr are identical. Both are defined as 1/760 of a standard atmosphere. The torr is named after Evangelista Torricelli, the inventor of the mercury barometer, while mmHg (millimeters of mercury) refers to the same measurement based on the height of a mercury column. The difference is less than 0.000015% — negligible for all ordinary applications.

Why is pascal so small for everyday use?

One pascal (Pa) equals one newton of force per square meter. Since a newton is about the weight of a small apple, and a square meter is a large area, 1 Pa is a very small pressure. A typical atmospheric pressure is 101,325 Pa. That's why kilopascal (kPa = 1,000 Pa) and megapascal (MPa = 1,000,000 Pa) are used for practical applications. Car tires are typically 200-250 kPa, while hydraulic systems operate at 10-30 MPa.

What pressure units are used in weather reports?

Weather reports use different units depending on the region. In the US, atmospheric pressure is reported in inches of mercury (inHg), e.g., '29.92 inHg is standard'. In Canada and most of Europe, it's reported in kilopascals (kPa) or hectopascals (hPa), where 1 hPa = 1 mbar. Meteorologists also use millibars (mbar), where 1 bar = 1000 mbar, and standard pressure is 1013.25 mbar.

How deep can humans go underwater before pressure becomes dangerous?

Pressure increases by about 1 bar (14.5 psi) every 10 meters of seawater. Recreational scuba divers typically stay within 40 meters (5 bar absolute pressure). At deeper depths, nitrogen narcosis and oxygen toxicity become serious risks. The deepest recorded scuba dive is 332 meters (34.3 bar) using special gas mixtures. Free divers (breath-hold) have reached depths of 214 meters, where the pressure compresses their lungs to a fraction of their normal size.

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