How do I convert psi to bar?

Multiply psi by 0.0689476. For example, 14.696 psi × 0.0689476 = 1.01325 bar (standard atmosphere). To convert bar to psi, multiply by 14.5038.

What is 1 atmosphere in Pa?

One standard atmosphere (atm) equals exactly 101,325 Pascals (101.325 kPa). It is approximately 14.696 psi, 1.01325 bar, or 760 mmHg.

What is the difference between mmHg and Torr?

They are nearly identical: 1 Torr is defined as 1/760 of a standard atmosphere, which equals 101325/760 ≈ 133.322 Pa. One mmHg is also 133.322 Pa by convention, making 1 Torr ≈ 1 mmHg for practical purposes.

What units are used for tire pressure?

In the United States, tire pressure is measured in psi (pounds per square inch). Most of the world uses bar or kPa. A typical car tire runs 30–35 psi, which is about 2.07–2.41 bar or 207–241 kPa.

Pressure Converter

Common pressure conversions

Value	Equivalent
1 atm	101,325 Pa = 14.696 psi = 1.01325 bar
1 bar	100,000 Pa = 14.504 psi = 0.9869 atm
1 psi	6,894.76 Pa = 0.0689 bar = 51.715 mmHg
1 kPa	1,000 Pa = 0.145 psi = 0.01 bar
760 mmHg	1 atm = 101,325 Pa
29.921 inHg	1 atm (standard)
1 MPa	1,000 kPa = 145.038 psi

How pressure conversion works

All conversions pass through Pascals (Pa) as the base SI unit. The input value is multiplied by the source unit's Pascal factor, then divided by the target unit's Pascal factor. For example, 1 atm = 101,325 Pa, and 1 psi = 6,894.757 Pa, so 1 atm = 101,325 ÷ 6,894.757 ≈ 14.696 psi.

Pressure units explained

Pascal (Pa) is the SI unit of pressure, equal to one Newton per square meter. Bar is 100,000 Pa and is commonly used in meteorology, engineering, and tire gauges in Europe. PSI (pounds per square inch) is the standard in the United States for tire pressure, hydraulics, and industrial equipment. mmHg / Torr are used in medicine (blood pressure) and vacuum systems.

Practical pressure reference

Application	Typical pressure
Sea level atmospheric pressure	1 atm = 101.325 kPa = 14.696 psi
Car tire (passenger vehicle)	~220–250 kPa (~32–36 psi)
Bicycle tire (road)	~550–900 kPa (~80–130 psi)
Normal blood pressure (systolic)	~120 mmHg (~16 kPa)
Scuba tank (full)	~20,000 kPa (~200 bar)
Deepest ocean (Mariana Trench)	~108,600 kPa (~15,750 psi)
Diamond anvil cell (lab)	> 1,000,000 bar (1 Mbar)

Gauge vs. absolute pressure

Absolute pressure is measured from true vacuum (0 Pa = perfect vacuum). Gauge pressure is measured relative to local atmospheric pressure (0 gauge = 1 atm absolute). Most everyday instruments — tire pressure gauges, blood pressure cuffs, HVAC gauges — read gauge pressure. Failure to distinguish between gauge and absolute causes errors in engineering calculations; always confirm which convention a formula or datasheet uses.

Conversion: Absolute = Gauge + Atmospheric (typically 101,325 Pa).

Vacuum levels

Vacuum is simply pressure below atmospheric. Common ranges:

Level	Pressure range	Typical application
Rough vacuum	1–100 mbar	Vacuum cleaners, food packaging
Medium vacuum	0.1–1 mbar	Freeze-drying, distillation
High vacuum	<0.1 mbar (<10 Pa)	CRT displays, electron microscopes
Ultra-high vacuum	<10⁻⁹ mbar	Particle accelerators, space simulation