Pressure conversion

About GeekFormat

1Kilopascal = 1000Pascal

1000

International System (SI)

Pascal (Pa)1000

Hectopascal (hPa)10

Kilopascal (kPa)1

Megapascal (MPa)0.001

Common Engineering

Bar (bar)0.01

Millibar (mbar)10

Standard Atmosphere (atm)0.009869

Millimeter of Mercury (mmHg)7.500617

Inch of Mercury (inHg)0.2953

Millimeter of Water (mmH₂O)101.971621

Kilogram-force/cm² (kgf/cm²)0.010197

Imperial

Pound-force/Square Inch (psi)0.145038

Free online pressure unit conversion tool, supporting two-way instant conversion of a total of 12 commonly used units, Pa, hPa, kPa, MPa, bar, mbar, psi, atm, mmHg, inHg, mmH₂O, kgf/cm². Enter any pressure value, and the results of other units will be displayed simultaneously in real time. It is suitable for organizing tire pressure, air compressor and hydraulic system, meteorological pressure, vacuum gauge and differential pressure readings. Note: This page is for unit conversion and will not help you determine gauge pressure, absolute pressure, differential pressure or material stress conditions. All calculations are done locally in the browser, and the data is not uploaded to the server.

Unit Converter

One-stop portal for 35+ types of unit conversions, suitable for switching back and forth across categories

Force Converter

Pressure formula P = F/A It is often necessary to unify the force unit first

Density Converter

Liquid column pressure and fluid calculations often deal with density and pressure at the same time

About pressure units and common usage contexts

Pressure is essentially the normal force endured per unit area, and the formula is often written as P = F/A. The standard unit of pressure in the International System of Units (SI) is the Pascal (Pa), defined as 1 N/m². Since 1 Pa is very small, decimal prefix units such as hPa, kPa, and MPa are more commonly used directly at engineering sites. The conversion on this page is to re-express the same physical quantity between different scales, and will not change its own working condition meaning.

In SI pressure unit, 1 hPa = 100 Pa, 1 kPa = 1000 Pa, 1 MPa = 1000000 Pa. hPa often appears in weather forecasts and sea level pressure charts, kPa is common in HVAC, building, and process systems, and MPa is suitable for hydraulics, high-pressure gases, and material strength scales. Since this page uses fixed factors for conversion, the conversion between these units is completely linear and there is no offset problem like temperature.

In addition to the SI system, you will also see a large number of engineering and historical units such as bar, mbar, psi, and kgf/cm² on site. The relationship between bar and kPa is perfect for the human brain to quickly estimate: 1 bar = 100 kPa. psi is still extremely common in U.S. tire, air conditioner, instrument and valve data. kgf/cm² has obvious traces of the old equipment era. Although it is close to bar, it is not equal. It is best not to mix them when entering reports.

In air pressure, vacuum and small differential pressure scenarios, liquid column units such as mmHg, inHg and mmH₂O are still very practical. They relate pressure to liquid column height and are therefore still common in blood pressure, vacuum, filter resistance, duct differential pressure, meteorology and experimental equipment. At the same time, if the same "100" represents 100 kPa, 100 mmHg, and 100 mmH₂O respectively, the magnitude difference will be very large, so it is important to confirm the unit first and then discuss the numerical value.

Another issue that is often overlooked is the reference zero point. Gauge pressure, absolute pressure, and differential pressure may all be written as kPa, bar, or psi, but they are not the same thing. Unit conversion can only deal with different "rulers" and cannot help you determine whether the value is relative to atmospheric pressure or relative to absolute vacuum. This page is suitable for numerical standardization, specification comparison and document organization. The original working condition description should still be retained before actually substituting into the formula or making safety judgments.

Use Cases

The tire pressure of automobiles, motorcycles, and bicycles can be quickly converted between psi, bar, and kPa. It is more convenient to set according to the door frame sticker or tire manual.
It is common to mix MPa, bar, and psi in the manuals of air compressors, hydraulic stations, cylinders, oil cylinders, and valve groups. Engineers can unify the units when organizing equipment accounts.
When repairing refrigeration and HVAC, change the psi/bar on the refrigerant pressure gauge. Change readings to kPa or MPa to facilitate comparison with manuals and training materials
Weather stations, airport METAR, and sea level air pressure data are commonly hPa, mbar, and inHg, which need to be unified when making cross-regional data comparisons
When reading medical or experimental materials, change mmHg to kPa to facilitate alignment with SI reports or paper templates
Vacuum pumps, laboratory filtration, distillation and packaging equipment commonly use inHg or mmHg. When purchasing instruments of different brands, they need to be compared with each other
For the performance of filters, air ducts, clean rooms and fans, mmH₂O or Pa is commonly used to represent differential pressure, and debugging personnel can quickly convert it into a unified dimension
Specifications for pressure transmitters, sensors and controllers may be given at the same time psi, bar, kPa, MPa, you need to check whether the range matches when selecting.
The pressure settings, alarm thresholds and report fields of boilers, gas tanks, reactors and process pipelines are often required to be unified into MPa or kPa
SCUBA Bar and psi coexist commonly in diving, gas cylinder filling, breathing air compressors and fire-fighting cylinders, making international data conversion easier
In material mechanics, fluid mechanics and thermodynamics operations, unifying atm, Pa, kPa and MPa and then substituting them into the formula can reduce orders of magnitude errors
When importing tire pressure gauges, pressure gauges, vacuum gauges or pump valve data purchased from abroad, first unify the unit to the system that the local team is accustomed to and then enter it into ERP or CMMS
Common on old machinery, Japanese equipment and factory nameplates kgf/cm², maintenance personnel need to change it to bar, kPa or MPa before doing on-site verification
When making multi-regional product manuals, training PPT or after-sales FAQ, write the same set of pressure data simultaneously as bar/psi/kPa to reduce problems that users cannot understand
When comparing US tire-pressure stickers, service manuals, or state inspection notes, replace psi with kPa or bar before setting the pressure.
When comparing hPa / inHg readings in NOAA, NWS, or airport ATIS reports with imported meters, unify the units first.
When creating a table for North American HVAC, tire-shop, or air-compressor service logs, unify psi, bar, kPa, and MPa before entering them.

How to Use

Fill in the known pressure value in the input box, supporting integers, decimals and signed readings.
Select the source unit in the drop-down box on the left, optional Pa, hPa, kPa, MPa, bar, mbar, psi, atm, mmHg, inHg, mmH₂O, kgf/cm².
Select the target unit in the drop-down box on the right, and the results will be updated immediately; you can click the middle swap button when you need to view it in reverse.
If you need horizontal comparison, expand all result panels and view the complete correspondence of the value under 12 pressure units at one time.

Features

Full coverage of 12 pressure units: SI series Pa/hPa/kPa/MPa, bar/mbar/kgf/cm² commonly used in engineering, psi common in British and American equipment, and scene units such as atm, mmHg, inHg, mmH₂O etc.
Two-way instant conversion: input any value, the source unit and target unit can be freely switched, the results are updated in real time, no need to click the conversion button
One-click exchange of source/target units: the middle exchange button can quickly view the reverse conversion, suitable for comparing equipment nameplates and specifications
Can be expanded to view all results: the results of the same pressure value in 12 units are displayed simultaneously in groups, making horizontal comparison more intuitive
Fixed conversion factors are transparent and traceable: for example, 1 bar = 100 kPa, 1 atm = 101.325 kPa, 1 psi ≈ 6.89476 kPa, convenient for engineering review
Covers multiple industry contexts: psi/bar is common in tires and air conditioners, hPa/mbar is common in meteorology, mmHg/inHg is common in medicine and vacuum gauges, and mmH₂O is common in air duct differential pressure
Supports integers, decimals and larger orders of magnitude numerical input, and can quickly convert from small differential pressure to MPa level high pressure
Pure browser local calculation: no network requests, no server logs, test data, equipment parameters and experimental records will not leave your device

How to choose a common pressure unit family?

It is the same pressure, but different units are more suitable for different scenarios. First choose the right expression, and then talk about numerical comparison.

Unit family	Representing the unit	The most common scenario	Why commonly used	This page supports
SI decimal system	Pa / hPa / kPa / MPa	Engineering calculations, papers, HVAC, hydraulics, material strength	Completely aligned with the International System of Units, the easiest way to unify reports and formulas across industries	Support
Engineering equipment system	bar / mbar / kgf/cm²	Pumps, valves, air compressors, boilers, old equipment nameplates	Intuitive readings, the most common in oral communication by field engineers and old equipment information	Support
British and American equipment systems	psi	Tire pressure, American instruments, refrigeration equipment, imported pressure gauges	British and American data and the North American market are still commonly used, and it is difficult to compare with local standards without conversion	Support
Atmospheric pressure context	atm / hPa / mbar / inHg	Meteorology, gas experiments, sea level pressure, aviation data	Strongly related to weather, standard conditions and pressure trend expression habits	Support
Liquid column and differential pressure context	mmHg / mmH₂O / inHg	Blood pressure data, vacuum gauge, filter resistance, air duct differential pressure	Easier to connect pressure with liquid column height or small range differential pressure	Support

Best Practices

First confirm whether it is gauge pressure, absolute pressure or differential pressure, and then do the unit conversion

kPa, bar, and psi are just rulers and will not tell you the reference zero point. Both gauge pressure and absolute pressure may be written as 100 kPa, but the engineering meaning is completely different. Preserve the original context before converting, such as "100 kPa(g)" or "100 kPa abs".

Use bar/psi for on-site communication, and try to unify it to kPa or MPa for formal calculations

Bar and psi are more convenient for equipment readings and after-sales communications, but it is more reliable to unify them into SI units when doing formula substitution, database storage, and specification standardization. A common practice is to use kPa/MPa in the report and keep the original reading in the remarks.

When you see kgf/cm², do not directly replace it verbally with bar

kgf/cm² is close to bar, but 1 kgf/cm² ≈ 0.980665 bar, which is not exactly the same. When calibrating old equipment, migrating alarm thresholds, or replacing instrument ranges, it is best to first change to kPa or MPa and then unify.

Prefer to keep mmH₂O or Pa for small differential pressures, do not blindly change to MPa

In scenarios of filter pressure loss, air duct static pressure and experimental micro-pressure, mmH₂O or Pa is more intuitive. Hardly writing tens of millimeters of water column as 0.0003 MPa is more difficult to read, and it is easier to copy the wrong decimal point.

If you are actually calculating P = F/A or P = ρgh, first unify the supporting quantities into the same unit

The pressure calculation constant appears together with force, area, density, and liquid column height. After the pressure units are unified, the supporting force or density units must also be unified, otherwise errors will still occur when formula substitution is made.

Force conversion Density conversion

Writing two sets of units at the same time in cross-regional documents can significantly reduce communication costs

For Chinese teams, MPa or kPa is often written, for North American customers, psi is often written, and for meteorological or aviation readers, hPa/inHg is often written. When external documents appear for the first time, two sets of units are given at the same time, which usually saves the cost of explanation.

FAQ

What units does this pressure converter support?

This page currently supports 12 pressure units: Pa, hPa, kPa, MPa, bar, mbar, psi, atm, mmHg, inHg, mmH₂O, kgf/cm². It covers mainstream writing in SI, Engineering, British and American Equipment, Atmospheric Pressure and Hydraulic Column Pressure. It should be noted that this page currently does not provide units such as Torr, GPa, ksi, etc., so when you see these units in the document, you need to change them to equivalent writing methods supported by the current page before processing.

1 bar is equal to how many kPa, MPa and psi?

1 bar = 100 kPa = 0.1 MPa = 100000 Pa, which is also approximately equal to 14.5038 psi and 0.986923 atm. Bar is a very common intermediate unit of magnitude on engineering sites, especially suitable for compressed air, pump valves, hydraulic and refrigeration pressure gauges. When you see that the equipment is nominally 6 bar, 8 bar, and 10 bar, convert it to MPa, which is 0.6 MPa, 0.8 MPa, and 1.0 MPa respectively.

1 psi equals how many kPa or bar?

1 psi ≈ 6.89476 kPa ≈ 0.0689476 bar, that is, 14.5038 psi is approximately equal to 1 bar. psi is a very common unit in British and American equipment, tire pressure gauges, air conditioning and refrigeration gauges, and air compressor manuals. There are several anchor points for daily memory: 30 psi ≈ 206.84 kPa ≈ 2.07 bar, 35 psi ≈ 241.32 kPa ≈ 2.41 bar.

What is 1 standard atmosphere (atm)?

1 atm = 101325 Pa = 101.325 kPa = 1.01325 bar = 760 mmHg ≈ 14.696 psi. atm is often used in basic physics, chemistry, thermodynamics and gas law textbooks to represent the standard atmospheric pressure reference value near sea level. When you see gas experimental conditions written as 1 atm or 2 atm, you can use this page to quickly unify them into kPa or bar, which are more commonly used in engineering.

What is the relationship between hPa and mbar? Why are they commonly used in weather forecasts?

In the units supported on this page, 1 hPa = 100 Pa, 1 mbar also = 100 Pa, so the hPa and mbar values are exactly the same. Meteorological fields have historically used mbar for a long time. After the subsequent switch to the SI system, a large number of scenarios were written in hPa, but the readings will not change. For example 1013.25 hPa is equal to 1013.25 mbar. These two writing methods are very common in weather maps, airport pressure, and sea level pressure correction values.

What scenarios are mmHg, inHg and mmH₂O suitable for?

mmHg is millimeters of mercury, commonly found in blood pressure data, laboratory vacuum gauges and some old-fashioned process instruments; inHg is inches of mercury, more common in British and American meteorology, aviation and vacuum equipment; mmH₂O It is millimeters of water column and is suitable for representing very small differential pressures, such as in air ducts, filters, ventilation systems and water column pressure heads. They all belong to the "liquid column pressure" writing method, which is convenient for linking the pressure with the actual liquid column height.

Can pressure and stress be directly regarded as the same thing?

They have the same dimensions and can be expressed in units such as Pa, kPa, and MPa, but the concepts are not exactly the same. Pressure emphasizes the normal load of fluid or gas on the surface, while stress emphasizes the internal stress state of the material. For example, the hydraulic system's 16 MPa and the steel's yield strength of 355 MPa cannot be directly compared to determine safety. This page is only responsible for numerical unit conversion and does not replace engineering calculations and material selection.

What is the difference between gauge pressure, absolute pressure and differential pressure? Will this page automatically process it?

It will not be processed automatically. This page only changes the unit and does not change the reference zero point of the pressure. Absolute pressure is based on absolute vacuum as the zero point, gauge pressure is based on the local atmospheric pressure as the zero point, and differential pressure is the difference between the two pressure points. Although the units of 1 MPa gauge pressure and 1 MPa absolute pressure are the same, their physical meanings are different. Before conversion, please confirm which pressure the original data belongs to, otherwise the value is correct and the engineering judgment may still be wrong.

What is kgf/cm²? Why are many old equipment still in use?

kgf/cm² means "kilogram force per square centimeter" and is a common historical unit on old engineering equipment, boilers, air compressors, and Japanese or Korean instruments. 1 kgf/cm² = 98066.5 Pa = 98.0665 kPa ≈ 0.980665 bar ≈ 14.2233 psi. It's close to bar, so it's often used colloquially in the field, but it's not exactly the same. When sorting out old equipment information, it is best to change it into kPa, MPa or bar.

Can vacuum gauge or negative pressure readings be converted here?

Yes, as long as you enter signed values, this page will still convert according to a linear scale. For example, if a vacuum gauge displays -20 inHg, you can directly change it to kPa or mmHg and continue sorting. It should be noted that negative pressure readings are usually "below atmospheric pressure" in the context of gauge pressure, not negative absolute pressure. Therefore, correct conversion values do not mean that the reference zero point problem has been solved.

Can this page be used offline? Will the data be uploaded?

Can be used offline. After the page is loaded, all pressure conversions are performed locally in the browser, with no network requests, no server logs, and no form submissions. The tire pressure, process parameters, experimental data and equipment settings you input will not be uploaded to the server, and the input will be cleared after closing the page.

Why do NOAA, NWS, or airport ATIS reports commonly use hPa or inHg, while equipment nameplates often use psi / bar?

Because meteorological, aviation and equipment service habits are different. Air pressures in NOAA, NWS, or airport ATIS reports are more often published in hPa or inHg, while tire, air compressor, HVAC, and inlet pressure gauges often read psi or bar. This tool is only responsible for converting the same pressure value into another unit, so that you can compare readings from different sources in the same table.

Can I directly change the psi on US tire-pressure stickers, service manuals, or state inspection notes to kPa?

Yes, as long as the raw reading itself is a pressure value, it can be directly converted linearly to kPa, bar or MPa. It should be noted that this step only changes the unit and will not judge the cold tire/hot tire standard or gauge pressure/absolute pressure difference for you. The actual settings should still be based on the original factory or local specifications.

Glossary

Pascal (Pa): SI pressure is basically written, 1 Pa = 1 N/m². It is also a common unit base for stress, elastic modulus, etc.
Hectopascal/mbar (hPa / mbar): 1 hPa = 100 Pa, 1 mbar = 100 Pa, the two values are exactly the same. Very common in meteorological and atmospheric pressure scenarios.
Kilopascal/MPa (kPa / MPa): 1 kPa = 1000 Pa, 1 MPa = 1000000 Pa. kPa is common in HVAC, process systems, and MPa is common in hydraulics, high-pressure equipment, and material strength.
bar: 1 bar = 100000 Pa = 100 kPa, which is one of the most common intermediate pressure units on engineering sites and equipment nameplates.
Pound force per square inch (psi): A common unit for British and American equipment, tires and pressure gauges, 1 psi ≈ 6.89476 kPa. It appears frequently in U.S. market data.
Standard atmospheric pressure (atm): 1 atm = 101325 Pa = 101.325 kPa, commonly used in the description of standard conditions in basic physics, chemistry and thermodynamics.
Millimeters of mercury/inch of mercury (mmHg / inHg): Liquid column pressure unit. mmHg is commonly found in blood pressure and experimental vacuum readings, and inHg is commonly found in British and American meteorological, aviation and vacuum equipment. 1 inHg = 25.4 mmHg.
Millimeters of water column (mmH₂O): A commonly used liquid column unit that represents small pressure differences, suitable for air ducts, filters, fans and ventilation systems. 1 mmH₂O = 9.80665 Pa.
Kilogram force per square centimeter (kgf/cm²): A common unit of old engineering equipment, 1 kgf/cm² = 98066.5 Pa ≈ 0.980665 bar. Commonly found on old nameplates and historical specifications.

Quick Check of Commonly Used Pressure Conversion Anchor Points

Remember these typical benchmark values, on-site mental calculation and review will be much faster.

Basic value	Equivalent expression	Common scenario
1 atm	101.325 kPa = 1.01325 bar = 760 mmHg ≈ 14.696 psi	Standard atmospheric pressure, chemistry and thermodynamics textbook
1 bar	100 kPa = 0.1 MPa ≈ 14.5038 psi ≈ 750.062 mmHg	Air compressor, pump valve, hydraulic and refrigeration equipment
1 psi	6.89476 kPa ≈ 0.0689476 bar ≈ 51.715 mmHg	Tire pressure, American instrument, North American specification book
1 kgf/cm²	98.0665 kPa ≈ 0.980665 bar ≈ 14.2233 psi	Old engineering equipment and historical nameplates
1 mmHg	133.322 Pa = 0.133322 kPa ≈ 0.0193368 psi	Blood pressure data, vacuum gauge, experimental readings
1 inHg	3.38639 kPa = 25.4 mmHg ≈ 0.0334211 atm	British and American meteorology, aviation and vacuum equipment

Quick check of commonly used pressure units in common scenarios

Scenarios	Common units	Why are they written like this
Car/Bicycle Tire Pressure	psi / bar / kPa	psi is common in North America, bar is common in Europe and maintenance stores, kPa is common in manufacturer's electronic systems kPa
Weather forecast and airport air pressure	hPa / mbar / inHg	hPa and mbar values are equal, British and American aviation data are often retained inHg
Hydraulic and pneumatic systems	MPa / bar / psi	High-pressure systems are more suitable for MPa. Bar or psi are commonly used for on-site verbal communication
Blood pressure and vacuum data	mmHg	Liquid column context has obvious historical inheritance, which is very common when reading literature and old instruments
Duct/filter differential pressure	Pa / mmH₂O	Small range, it is more intuitive to directly use Pa or millimeters of water column
Material strength and force	MPa	Share the magnitude with the stress and strength table to facilitate the unification of engineering drawings and material manuals

Privacy & Security

All pressure conversions on this page are done in your browser. The tire pressure, process pressure, experimental readings and equipment parameters you enter will not leave your device - there are no network requests, no server logs, and the input will be cleared after closing the page. For sensitive data such as on-site debugging, quotation comparison and experimental records, this page will not collect or store any content.