Pressure Unit Converter

What exactly is 2.2 bar on a car tire in psi?

What exactly is 2.2 bar marked on the side of a car tire in psi? Our pressure unit converter can instantly tell you: 2.2 bar is approximately 31.9 psi. Conversions like this appear repeatedly every day in car maintenance, weather charts, and engineering drawings. Pressure describes the perpendicular force applied per unit area; the international unit pascal (Pa) is defined as the pressure produced by 1 newton of force uniformly applied over 1 square meter. In the real world, different industries and regions prefer different units: European pressure gauges typically use bar, North American tire shops use psi, weather forecasts use hectopascals (hPa) or millibars (mbar), and hospital blood pressure monitors use millimeters of mercury (mmHg). Our converter covers 14 common pressure units. Simply input a number, select the original unit, and all conversion results for the remaining 13 units appear instantly.

Conversion Principle — All Units Have a Conversion Factor

The basic principle of pressure unit conversion is very simple: every pressure unit has a fixed conversion factor with respect to the reference unit pascal (Pa). Convert your input value to Pa first, then multiply by the conversion factor of the target unit to get the result you need. Here are some of the most common relationships:

• 1 bar (bar) = 100,000 Pa
• 1 standard atmosphere (atm) = 101,325 Pa
• 1 pound-force per square inch (psi) = 6,894.76 Pa
• 1 millimeter of mercury (mmHg, 0 °C) = 133.322 Pa

In our converter, all calculations are completed locally in your browser, and you can choose precision from 0 to 10 decimal places. While the formula is simple, memorizing all 14 × 14 unit relationships is impractical — that's why this converter is so useful.

Complete a Conversion in 4 Steps

Open the pressure unit converter page and you'll see a simple input area with a results list below. The process takes just 4 steps:

1. Enter the number: In the input field at the top, enter the pressure value you want to convert, for example 1.
2. Select the original unit: In the first dropdown menu, find the unit corresponding to your number. Units are organized by SI units, meteorological units, imperial units, etc. For example, select "standard atmosphere (atm)".
3. Set decimal places: In the second dropdown menu, choose a precision level, such as 2 (two decimal places).
4. View the results immediately: No button click needed — all conversion values for the other 13 units appear instantly below. Each row has a copy icon on the right; click it to copy the result.

Complete Example: What numbers can 1 atmosphere produce?

Let's walk through the process with 1 standard atmosphere. Enter 1 in the input field, select "standard atmosphere (atm)" from the first dropdown, and choose 2 for precision. The results list immediately shows:

• 101,325.00 pascal (Pa)
• 101.33 kilopascals (kPa)
• 0.10 megapascals (MPa)
• 1.01 bar (bar)
• 1,013.25 millibars (mbar) / hectopascals (hPa)
• 14.70 pounds-force per square inch (psi)
• 2,116.22 pounds-force per square foot (psf)
• 760.00 millimeters of mercury (mmHg)
• 10,332.27 millimeters of water (mmH₂O)
• 1.03 kilogram-force per square centimeter (kgf/cm²)

These values can cross-verify each other: 1 atm ≈ 1.01325 bar, 1 atm = 760 mmHg — exactly the relationships meteorology mentions. If you change the precision to 4 in the same interface, the psi line becomes 14.6959, allowing you to use it directly in high-precision engineering reports.

Here's another comparison example. A family car's recommended tire pressure is shown as 250 kPa. Enter 250 in the input field, select "kilopascals (kPa)" as the original unit, and set precision to 1. You'll see:

• 2.5 bar (bar)
• 36.3 pounds-force per square inch (psi)
• 1,875.2 millimeters of mercury (mmHg)
• 0.25 megapascals (MPa)

With this results sheet, you can report the pressure value in any tire shop worldwide that your client will understand.

Pressure Unit Quick Reference Table

If you just need to look up a few common conversions, you can use this table directly:

All values above can be obtained with more significant figures by adjusting the precision in the converter.

When Will You Use It?

Automobiles and Cycling: Most passenger car tire pressures fall between 2.0–3.0 bar (approximately 29–44 psi). When comparing a European car's nameplate with a North American pump gauge, use our psi ↔ bar converter to see exactly how much you should inflate.

Weather Observation: Atmospheric pressure on weather maps is often marked in hectopascals (hPa) or millibars (mbar). Standard sea-level pressure of 1,013.25 hPa equals 1 atmosphere. Use the converter to quickly compare different units in historical weather records.

Engineering and Materials: Concrete specifications, pipe pressures, and hydraulic system manuals often mix MPa, bar, and kgf/cm². In a material test report, you can input the measured MPa value and instantly see the equivalent in other units, avoiding unit magnitude mistakes.

5 Common Pitfalls to Avoid

• Confusing absolute pressure and gauge pressure: psi is often distinguished as psia (absolute pressure) and psig (gauge pressure, relative to local atmospheric pressure). This converter only performs numerical unit conversion and does not automatically subtract atmospheric pressure. If your pressure gauge reading is gauge pressure, the converted value remains gauge pressure — only the unit changes.
• Ignoring temperature conditions for mmHg: The standard definition of millimeter of mercury (mmHg) uses the mercury density at 0 °C, corresponding to 133.322 Pa. Medical blood pressure monitors or laboratory readings at different temperatures may show slight variations; this tool uses the standard conversion factor.
• Capitalization errors: The P in Pa, kPa, MPa must be uppercase; bar and mbar are entirely lowercase. Writing 1 pa or 1 KPA would be rejected in academic literature, and while the converter's numerical input isn't affected, unit names must be correctly recognized from the dropdown menu.
• Setting precision too high: For everyday tire pressures or weather forecasts, 1–2 decimal places are sufficient. Setting 10 decimal places produces trailing digits with no practical meaning and is easy to misread.
• Treating kgf/cm² as standard atmosphere: 1 kgf/cm² (engineering atmosphere, at) is approximately 0.9678 atm, slightly less than standard atmosphere. This unit appears in boiler and old pipe drawings; don't directly equate it to atm during conversion.

Notes and Limitations

This tool is based on internationally recognized fixed conversion coefficients (such as 1 atm = 101,325 Pa), and all calculations are performed locally in your browser without relying on the internet or storing your data. To be clear:

• Does not include altitude, temperature, or gravity corrections: Atmospheric pressure depends on altitude and temperature; mercury and water column pressures also depend on local gravitational acceleration. The converter only performs standard-condition numerical conversions and does not replace physical measuring instruments.
• Not suitable for legal metrology certification: If conversion results are used in trade settlement, safety valve calibration, medical health standards, or other scenarios requiring metrology certification documents, use data from official metrology inspection agencies as the authoritative source. This tool is for reference only.
• Floating-point precision at extreme boundaries: While you can input any real number, when values approach zero or reach extremely high orders of magnitude, floating-point arithmetic may introduce rounding errors. For critical applications, verify that the order of magnitude is reasonable.

Frequently Asked Questions (FAQ)

How many pascals equal 1 standard atmosphere?
In our converter, 1 atm is fixed at 101,325 Pa. This is the standard value set by the International Organization for Standardization; "one atmosphere" in weather forecasts refers to this value.

How do you convert between psi and bar?
1 psi ≈ 0.0689476 bar, and 1 bar ≈ 14.5038 psi. If you set the original unit to psi in the converter, enter a number, and the bar row shows the result — and vice versa.

Is the relationship between millimeter of mercury (mmHg) and pascal (Pa) fixed?
Under standard gravitational acceleration and mercury density at 0 °C, 1 mmHg = 133.322 Pa. Both medical and meteorological data use this coefficient, and our tool converts using this relationship.

What does the precision setting in the converter affect?
The precision dropdown controls the number of decimal places in the results. For example, choosing 2 displays psi as 14.70; choosing 4 displays 14.6959. The core calculation precision remains unchanged; only the displayed number is rounded to the specified number of decimal places.

Will the numbers I enter be uploaded and saved?
No. All calculations are completed in real-time in your browser and do not pass through a server. Your inputs and results are not recorded by us.

Can I compare multiple units' results at once?
Yes. After entering a value and selecting the original unit, all conversion results for the other 13 units appear below instantly. You can see all unit values at once without switching back and forth.

Now try your own numbers in the calculator above — whether it's tire pressure, cylinder pressure, or millibars on a weather chart, you'll understand instantly.