Pressure Converter: How to Convert Between PSI, Bar, Pascal, and Atmospheres

Pressure measurements pop up everywhere: checking your car tires (PSI), reading weather forecasts (bar or millibars), working on engineering projects (pascal), or scuba diving (atmospheres). Each field uses its own preferred unit, and converting between them can be confusing without a reference. Our Pressure Converter handles all common units instantly, but understanding the relationships helps you estimate on the fly and catch errors before they matter.

Pressure Units Reference Table

Unit	Symbol	Common Use	Equivalent (1 atm)
Pascal	Pa	SI unit, engineering, science	101,325 Pa
Kilopascal	kPa	Weather, engineering	101.325 kPa
Bar	bar	Weather, industrial, scuba	1.01325 bar
Millibar	mbar	Weather maps, meteorology	1,013.25 mbar
PSI	psi	Tire pressure, US/UK equipment	14.696 psi
Atmosphere	atm	Reference standard, diving	1 atm (by definition)
Torr / mmHg	Torr	Vacuum measurement, blood pressure	760 Torr

Real-World Pressure Examples

• Car tires: Typical car tires need 30–35 PSI (2.07–2.41 bar). Truck tires: 50–80 PSI
• Bicycle tires: Road bikes: 80–130 PSI (5.5–9 bar). Mountain bikes: 30–50 PSI (2–3.4 bar)
• Blood pressure: Normal reading: ~120/80 mmHg (16/10.7 kPa). Measured in Torr/millimeters of mercury
• Weather: Standard sea-level atmospheric pressure: 1,013.25 mbar or 29.92 inHg. A low-pressure system: ~990 mbar. Hurricane: can drop below 920 mbar
• Scuba diving: Every 10 meters of seawater adds about 1 atm of pressure. At 30m, you experience 4 atm total
• Espresso machines: 9 bars of pressure (130 PSI) is the standard for pulling espresso shots
• Compressed air tools: Most pneumatic tools run at 90 PSI (6.2 bar)

Use our Pressure Converter to get precise conversions between any pressure units for your specific use case.

Quick Conversion Cheat Sheet

• 1 bar ≈ 14.5 PSI (exact: 14.504)
• 1 atm = 14.696 PSI ≈ 1.013 bar ≈ 101.3 kPa
• 1 PSI = 6,895 Pa ≈ 0.069 bar
• 1 kPa = 0.145 PSI
• 1 mmHg ≈ 133.3 Pa
• 1 mbar = 0.001 bar = 100 Pa

How to Convert Pressure Manually

The key insight is that all conversions flow through one anchor value: 1 standard atmosphere = 101,325 Pa. To convert between any two units, first convert to pascals, then to the target unit. For example, to convert 35 PSI to bar: 35 × 6,895 = 241,325 Pa, then 241,325 ÷ 101,325 × 1.01325 ≈ 2.41 bar. That two-step method works for every unit pair, which is why the converter is faster for anything beyond the most common pairs.

When Precision Matters Most

• Scuba diving: Getting atmospheres wrong is a safety issue — decompression calculations depend on absolute pressure
• Engineering: Pressure vessel design, hydraulic systems, and pneumatic circuits need exact values, not rounded estimates
• Medical: Blood pressure readings in mmHg and ventilator pressures in cmH₂O must not be mixed up
• Meteorology: Millibar vs inHg mix-ups in weather reporting can mislead storm tracking

For exact conversions, visit the Pressure Converter — it supports PSI, bar, kPa, atm, Torr, and more, so you always get the unit your field actually uses.