Pressure Converter
Pascal, bar, psi, atm and mmHg.
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Result
14.50377377 psi
1 bar in pound per square inch
1 bar = 14.50377377 psi
Pressure Conversion Math Formula
Pressure is force per area, so one pascal is one newton pressing on one square metre. The family is a mix of metric, imperial and historic units, but the method does not change: multiply by a factor that equals 1, passing through pascals.
Some units look unrelated, and they are, until you see where they come from. A psi is a pound of force on a square inch. A millimetre of mercury is the pressure at the bottom of a 1 mm column of mercury. Each has been fixed to an exact number of pascals, and that number is what the converter uses.
The formula
value in B = value in A × (Pa per A) ÷ (Pa per B)1 atm = 101,325 Pa = 1.01325 bar = 760 mmHg = 14.6959 psi
Worked example 1: A 32 psi tyre, in bar
32 psi × (6,894.757293 Pa ÷ 1 psi) = 220,632.2 Pa220,632.2 Pa × (1 bar ÷ 100,000 Pa)Answer: 2.20632 bar
So 32 psi is about 2.2 bar, a common pressure for a car tyre.
Worked example 2: One standard atmosphere, in psi
1 atm × (101,325 Pa ÷ 1 atm) = 101,325 Pa101,325 Pa × (1 psi ÷ 6,894.757293 Pa)Answer: 14.6959 psi
The same 101,325 Pa divided by 133.322387 Pa per mmHg gives 760 mmHg, which is how the atmosphere was originally defined.
Worked example 3: A blood pressure reading of 120 mmHg, in kPa
120 mmHg × (133.322387 Pa ÷ 1 mmHg) = 15,998.7 Pa15,998.7 Pa × (1 kPa ÷ 1,000 Pa)Answer: 15.9987 kPa
A reading of 120 over 80 mmHg is therefore about 16 over 10.7 kPa, the form used in some countries.
Common mistakes to avoid
- Gauge against absolute pressure. A tyre gauge reads pressure above the surrounding air. A reading of 32 psi gauge is about 46.7 psi absolute (32 + 14.696). Formulas like the gas law need absolute pressure. This converter changes units only. It does not add or remove the atmosphere.
- Treating bar and atmosphere as equal. They are close but not the same: 1 atm = 1.01325 bar, a difference of 1.3%. That rarely matters for weather or tyres, and it can matter in lab or engineering work.
- Expecting psi to be a small number. One psi is 6,895 Pa, roughly 6.9 kPa. The pascal itself is tiny, about the pressure of a banknote lying flat on a table, so kPa and bar are the usual working units.
About pressure units
Pressure is force spread over an area. The SI unit is the pascal (Pa), one newton per square metre. Because a pascal is small, weather maps use hectopascals (100 Pa, the same as a millibar), engineers use kilopascals and megapascals, and car tyres use bar or psi.
Standard atmospheric pressure at sea level is defined as exactly 101,325 Pa. Blood pressure and old barometers use millimetres of mercury, where a column of mercury 760 mm high balances one atmosphere. Aviation altimeters and some weather reports use inches of mercury.
- Pascal (Pa)One newton per square metre. The SI unit.
- Kilopascal (kPa)1 kPa = 1,000 PaA thousand pascals. Used in engineering, tyre pressure and weather in many countries.
- Bar (bar)1 bar = 100,000 PaExactly 100,000 Pa. Very close to one atmosphere.
- Atmosphere (atm)1 atm = 101,325 PaExactly 101,325 Pa, the standard pressure at sea level.
- Pound per square inch (psi)1 psi = 6,894.757293 PaOne pound-force per square inch. Used for US tyres, air tools and hydraulics.
- Millimetre of mercury (mmHg)1 mmHg = 133.3223874 PaThe pressure of a 1 mm column of mercury. Used for blood pressure and vacuum.
- Inch of mercury (inHg)1 inHg = 3,386.389 PaThe pressure of a 1 inch column of mercury. Used in US weather reports and altimeters.
Pressure conversion table
| Value | kPa | bar | psi | mmHg |
|---|---|---|---|---|
| 1 kPa | 1 | 0.01 | 0.145038 | 7.50062 |
| 1 bar | 100 | 1 | 14.5038 | 750.062 |
| 1 atm | 101.325 | 1.01325 | 14.6959 | 760 |
| 1 psi | 6.89476 | 0.0689476 | 1 | 51.7149 |
| 1 mmHg | 0.133322 | 0.00133322 | 0.0193368 | 1 |
| 1 inHg | 3.38639 | 0.0338639 | 0.491154 | 25.4 |
Pressure converter FAQ
How do I convert psi to bar?
Multiply by 0.0689476, or divide by 14.5038. 30 psi is 30 × 0.0689476 = 2.07 bar.
How do I convert bar to psi?
Multiply by 14.5038. A 2.5 bar tyre is 2.5 × 14.5038 = 36.26 psi.
What is standard atmospheric pressure?
101,325 Pa. That is 101.325 kPa, 1.01325 bar, 760 mmHg, 29.92 inHg or 14.696 psi at sea level.
What is the difference between gauge and absolute pressure?
Gauge pressure is measured relative to the surrounding atmosphere, absolute pressure relative to a perfect vacuum. Absolute = gauge + atmospheric. A flat tyre reads 0 psi gauge but is still about 14.7 psi absolute.
How many kPa is one psi?
6.895 kPa. So 14.5 psi is very close to 100 kPa, which is just under 1 bar.
Why is blood pressure measured in mmHg?
The first accurate gauges balanced the pressure against a column of mercury, and readings stayed in millimetres of it. The unit is not SI, but it is fixed at 133.322 Pa and clinicians kept it. 120 mmHg is about 16 kPa.