Pressure Unit Converter
Convert pressure between SI, engineering, atmospheric, vacuum, and mercury-column units. Enter ordinary decimals, signed gauge values, or scientific notation, then swap units without changing the represented pressure.
Signed values are supported for gauge and differential pressure.
Enter a pressure value.
Select the source and target units to see the converted result.
How to Use the Pressure Converter
Enter the pressure value, select the source unit, and choose the unit you want to convert to.
Use the swap control to reverse the units. A valid converted value becomes the new input so the physical pressure remains unchanged.
Signed values are supported for gauge and differential pressure. Scientific notation such as 2.5e6 is also accepted.
How Pressure Conversion Works
Every value is first converted to pascals using the source unit's pascals-per-unit factor.
The pascal value is then divided by the target unit's factor.
Using one common reference avoids repeatedly converting through shortened intermediate values.
Supported pressure units
Swipe horizontally to view the full table.
Pascal and SI Pressure Units
The pascal, symbol Pa, is the SI derived unit of pressure and equals one newton per square metre.
The unit is named after Blaise Pascal and is commonly used with prefixes because one pascal is relatively small.
One hectopascal is 100 Pa, one kilopascal is 1,000 Pa, and one megapascal is 1,000,000 Pa.
Bar, Millibar, and Hectopascal
One bar equals exactly 100,000 Pa.
One millibar equals exactly 100 Pa, making one millibar numerically equal to one hectopascal.
Bar is common in engineering and process systems, while hPa and mbar are widely recognised in atmospheric-pressure reporting.
PSI and Standard Atmosphere
Pounds per square inch expresses one pound-force distributed over one square inch.
One psi equals approximately 6,894.757293 Pa.
The standard atmosphere is a fixed reference equal to exactly 101,325 Pa. Actual outdoor pressure varies with altitude, weather, and location.
Torr, mmHg, and inHg
One Torr is exactly one seven-hundred-and-sixtieth of a standard atmosphere.
The conventional millimetre of mercury uses a slightly different pressure factor. Torr and mmHg are therefore close but not mathematically identical in this converter.
Millimetres of mercury remain common in medicine, while Torr is widely used in vacuum work. Inches of mercury appear in aviation, weather reporting, and vacuum measurement.
Absolute, Gauge, and Differential Pressure
Absolute pressure is referenced to a perfect vacuum and should not be negative.
Gauge pressure is referenced to surrounding atmospheric pressure and can be negative below that reference.
Differential pressure compares two pressures and can have either sign depending on the chosen direction.
Changing units does not change which reference the original measurement uses.
Pressure reference types
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Common Pressure Conversions
The table uses the same conversion factors as the live calculator.
Displayed values are rounded to no more than four decimal places, while the internal result remains unrounded for swapping.
Common pressure conversions
Swipe horizontally to view the full table.
Precision and Measurement Uncertainty
An exact unit definition does not make a measured input exact.
Instrument calibration, resolution, temperature, pressure reference, and measurement procedure determine the practical uncertainty.
Avoid reporting more converted digits than the original measurement can support.
Safety and Medical Limits
A unit conversion does not establish a safe tyre pressure, vessel rating, hydraulic limit, diving profile, vacuum procedure, or process setting.
Millimetres of mercury can express blood pressure, but this converter does not interpret readings or provide medical advice.
Privacy and Local Processing
The conversion runs entirely in the browser.
Pressure values and unit selections are not uploaded, added to a public URL, or permanently stored.
Pressure Conversion Formulas
All supported units are converted through their pascals-per-unit factors.
Formula variables
- Pressure in the selected source unit
- Equivalent pressure in pascals
- Converted pressure in the target unit
- Pascals represented by one source unit
- Pascals represented by one target unit
Examples
Convert atmosphere to kilopascals
1Input
1 atm
Show result
Result
101.325 kPa
Convert bar to psi
2Input
1 bar
Show result
Result
14.5038 psi
Convert tyre pressure
3Input
32 psi
Show result
Result
220.6322 kPa
The result does not determine the correct pressure for a particular tyre.
Convert megapascals to psi
4Input
1 MPa
Show result
Result
145.0377 psi
Convert blood-pressure units
5Input
120 mmHg
Show result
Result
15.9987 kPa
This is a unit conversion, not medical interpretation.
Convert vacuum pressure
6Input
760 Torr
Show result
Result
1 atm
Convert negative gauge pressure
7Input
-20 kPa
Show result
Result
-2.9008 psi
The negative sign is preserved.
Frequently Asked Questions
What is the SI unit of pressure?
The pascal, symbol Pa. One pascal equals one newton per square metre.
How many kPa are in one psi?
One psi equals approximately 6.8948 kPa.
How many psi are in one bar?
One bar equals approximately 14.5038 psi.
How many psi are in one MPa?
One megapascal equals approximately 145.0377 psi.
How many pascals are in one atmosphere?
One standard atmosphere equals exactly 101,325 Pa.
Are hPa and mbar equal?
Yes. One hectopascal and one millibar both equal exactly 100 Pa.
Are Torr and mmHg exactly equal?
No. They are extremely close, but this converter uses their distinct defined or conventional factors.
Can pressure be negative?
Gauge and differential pressure can be negative relative to their reference. Absolute pressure should not be negative.
Does one atmosphere equal actual outdoor pressure?
No. A standard atmosphere is a fixed reference. Actual air pressure changes with altitude, weather, and location.
Why does the result show four decimal places?
Four decimal places retain useful conversion precision without producing unnecessarily long results. Very small or large values use scientific notation.
What does Swap do?
It reverses the selected units and carries the exact converted value into the new source field before display rounding.
Are my pressure values uploaded?
No. Conversion happens locally in the browser.
References
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