Pressure Converter (Pa, bar, PSI, atm, mmHg, ...)
Convert a pressure between pascal, hectopascal, kilopascal, bar, PSI, atmosphere, torr, mmHg, and inHg. Useful for tire pressure, weather readings, diving, and blood pressure. Everything runs in your browser.
How the conversion works
Every unit on this page is defined by how many pascals it represents. The pascal is the SI unit of pressure, defined as one newton of force per square meter. The input is converted to pascals, then from pascals into the target unit:
result = value × (Pa per source unit) ÷ (Pa per target unit)
A pascal is a very small amount of pressure, which is why practical units are almost always multiples: 1 hPa = 100 Pa, 1 kPa = 1000 Pa, and 1 bar = 100,000 Pa.
Gauge pressure versus absolute pressure
This distinction causes more real-world confusion than any unit conversion, and no converter can resolve it for you, because it depends on what your instrument measures.
Absolute pressure is measured against a vacuum. Gauge pressure is measured against the surrounding atmosphere, so it reads zero when the object is at ambient pressure.
A car tire inflated to "2.2 bar" is at 2.2 bar gauge, meaning 2.2 bar above atmospheric. In absolute terms it holds about 3.2 bar. A completely flat tire reads 0 bar gauge but still contains air at roughly 1 bar absolute. Units are sometimes marked to indicate this, such as "barg" or "psig" for gauge and "bara" or "psia" for absolute, but the marking is frequently omitted. When a figure matters, check which reference it uses.
Quick reference table
| From | Pascal | hPa / mbar | bar | PSI |
|---|---|---|---|---|
| 1 Pa | 1 | 0.01 | 0.00001 | 0.000145 |
| 1 hPa | 100 | 1 | 0.001 | 0.014504 |
| 1 kPa | 1000 | 10 | 0.01 | 0.145038 |
| 1 bar | 100,000 | 1000 | 1 | 14.5038 |
| 1 PSI | 6894.76 | 68.9476 | 0.068948 | 1 |
| 1 atm | 101,325 | 1013.25 | 1.01325 | 14.6959 |
| 1 torr | 133.322 | 1.33322 | 0.001333 | 0.019337 |
| 1 mmHg | 133.322 | 1.33322 | 0.001333 | 0.019337 |
| 1 inHg | 3386.39 | 33.8639 | 0.033864 | 0.491154 |
Note that 1 hPa and 1 mbar are exactly the same amount of pressure. Both units survive in weather reporting for historical reasons, hectopascal is the official SI-derived form, millibar the older meteorological convention.
Practical examples
Tire pressure
European cars specify tire pressure in bar, US vehicles in PSI. A typical passenger car runs 2.2 to 2.5 bar, which is 32 to 36 PSI. The conversion is roughly bar × 14.5 = PSI. Since correct tire pressure affects fuel consumption, handling, and tire life, it is worth converting precisely rather than estimating, and checking pressures when the tires are cold.
Weather and air pressure
Barometric pressure is reported in hectopascals or millibars in most of the world and in inches of mercury in the US. Standard sea-level pressure is 1013.25 hPa, which equals 29.92 inHg. High-pressure systems typically run above 1020 hPa and bring settled weather, low-pressure systems below 1000 hPa and bring unsettled conditions.
Blood pressure
Medicine has kept mmHg, a legacy of mercury column manometers. A reading of 120/80 mmHg corresponds to 16.0/10.7 kPa. Some countries and some research literature use kilopascals, but mmHg remains the clinical standard almost everywhere.
Diving
Water pressure increases by approximately 1 bar for every 10 meters of depth. At 30 m a diver is under about 4 bar absolute: 1 bar of atmosphere plus 3 bar of water. This relationship underlies gas consumption calculations and decompression planning, since the gas in a diver's lungs is compressed proportionally.
Frequently asked questions
How many PSI is 1 bar?
14.5038 PSI. In the other direction, 1 PSI is 0.0689 bar. For quick mental math, multiplying bar by 14.5 is accurate enough for tire pressures.
Is 1 hPa the same as 1 mbar?
Yes, exactly. They are two names for the same amount of pressure. Weather services use both interchangeably, with hectopascal being the formally preferred SI-derived unit.
What is standard atmospheric pressure?
101,325 Pa, defined exactly. That equals 1013.25 hPa, 1.01325 bar, 14.6959 PSI, 760 mmHg, or 29.92 inHg. It represents average pressure at sea level.
What is the difference between torr and mmHg?
They agree to within about 0.000015%, so they are interchangeable in practice. Torr is defined as exactly 1/760 of a standard atmosphere, while mmHg derives from the density of mercury under standard gravity. This converter keeps them separate for correctness, but no practical measurement can distinguish them.
Why is my tire pressure gauge reading different from the absolute pressure?
Because tire gauges measure gauge pressure, the amount above atmospheric. Add roughly 1 bar (14.7 PSI) to convert a gauge reading to absolute pressure.
How much does pressure increase underwater?
About 1 bar per 10 meters of depth in seawater, on top of the 1 bar of atmospheric pressure at the surface. At 20 m, total absolute pressure is roughly 3 bar.
Related converters
- Force converter, since pressure is force per unit area
- Area converter, for the area component of a pressure calculation
- All unit converters