What the Pressure Converter Does and Who It's For

This pressure converter changes a value from one unit to another across the five units people use most: pascal (Pa), bar, pounds per square inch (psi), standard atmosphere (atm), and millimeters of mercury (mmHg). Enter a number, pick the unit you have and the unit you want, and the tool returns the equivalent.

It is built for everyday and technical needs alike: checking tire pressure (psi or bar), reading a weather barometer (mbar, mmHg, or hPa), sizing HVAC and plumbing systems (psi to kPa), interpreting blood pressure or vacuum readings (mmHg), and converting lab or engineering data into SI units (pascal). If you frequently search for 'bar to psi' or 'psi to kPa', this handles those conversions in one place.

How the Pressure Converter Works (The Formula)

Pressure is force per unit area, and the SI base unit is the pascal (1 Pa = 1 newton per square meter). The converter works by routing every conversion through the pascal as a common base. It first converts your input to pascals, then converts pascals to your target unit.

The exact factors used are:

1 bar = 100,000 Pa (exactly)
1 atm = 101,325 Pa (exactly, by definition)
1 psi = 6,894.76 Pa
1 mmHg = 133.322 Pa
1 kPa = 1,000 Pa

The Two-Step Conversion Method

Mathematically, the general rule is: value_to = value_from x (Pa per from-unit) / (Pa per to-unit).

So to go from bar to psi, you multiply by 100,000 (Pa per bar) and divide by 6,894.76 (Pa per psi). To go from psi to kPa, you multiply by 6,894.76 and divide by 1,000. This base-unit approach means any unit can convert to any other without needing a separate factor for every possible pair.

Worked Example: 2.4 bar to psi

Suppose your car door label lists a recommended tire pressure of 2.4 bar and your gauge reads in psi. Convert it step by step:

Step 1 - to pascals: 2.4 bar x 100,000 = 240,000 Pa. Step 2 - to psi: 240,000 / 6,894.76 = 34.81 psi. So 2.4 bar is about 34.8 psi.

A second quick check, psi to kPa: a tire at 32 psi equals 32 x 6,894.76 = 220,632 Pa, or about 220.6 kPa. The same number is also roughly 2.21 bar.

Tips, Common Mistakes, and Factors That Affect the Result

The most frequent error is confusing gauge pressure with absolute pressure. A tire gauge or many industrial sensors read gauge pressure (pressure above the surrounding air), while atm and most barometric readings are absolute (measured from a vacuum). To convert gauge to absolute, add roughly 1 atm (101.325 kPa, about 14.7 psi). This converter does the unit math only; it does not add or subtract that offset for you.

Other points to keep in mind:

Do not confuse bar with millibar (mbar) or hectopascal (hPa); weather pressure near 1013 is in hPa/mbar, which equals about 1.013 bar.
Tire pressure changes with temperature, roughly 1 psi for every 10 degrees F (about 5.5 degrees C). Check tires cold for an accurate reading.
mmHg and torr are essentially equal (1 torr = 1 mmHg to within 0.000015 percent), so the converter treats them as interchangeable.
Keep an extra decimal place during conversion and round only the final answer to avoid compounding small errors.