Pressure Converter
Convert between PSI, bar, Pascal, atmosphere and mmHg — with a tyre pressure guide, weather pressure reference and blood pressure context.
PRESSURE CONVERTER
SI units
Everyday & engineering
Scientific & medical
🚗 Tyre pressure guide
Enter a pressure — or pick a vehicle below
Enter a pressure to see a real-world comparison
Famous pressures — click to load
Step-by-step solution
Type a pressure to see the conversion working
🌤️ Weather pressure reference
Standard atmosphere = 1013.25 mbar. Pressure > 1020 mbar = high pressure (fair weather); < 1000 mbar = low (unsettled).
❤️ Blood pressure & mmHg
Blood pressure is always quoted in mmHg (millimetres of mercury). A reading of 120/80 mmHg means 120 mmHg systolic (heart pumping) and 80 mmHg diastolic (heart resting).
Key pressure facts
Real-world pressures
Pressure Converter Explained
Core concepts, classroom applications, and plain-English explanations for all audiences.
Where you'll actually use this
Check your car tyres: the sticker inside the door frame gives the recommended pressure in PSI or bar. Weather apps quote atmospheric pressure in millibars (mbar) or hPa — they're the same unit. Blood pressure readings use mmHg. Every time a scuba diver goes 10 m deeper, the pressure increases by roughly 1 atmosphere. Pressure is everywhere.
Worked example
"Your car manual says 32 PSI rear tyres. The garage pump only shows bar. What do you set it to?"
32 PSI ÷ 14.504 = 2.21 bar
Or: 32 × 0.06895 = 2.21 bar
Result: Set the pump to 2.2 bar
Quick rule: 1 bar ≈ 14.5 PSI. So 30 PSI ≈ 2.07 bar, 35 PSI ≈ 2.41 bar.
Key pressure contexts
- → Weather: Standard atmospheric pressure = 1013.25 hPa. Low pressure (below 1000 hPa) usually means rain; high pressure means settled weather.
- → Blood pressure: A reading of 120/80 mmHg — the '120' is systolic (heart contracting), '80' is diastolic (resting). Normal range is well-defined in mmHg.
The formula: P = F ÷ A
Pressure = Force ÷ Area. A stiletto heel (small area) exerts far more pressure on a floor than a flat shoe of the same weight — the force is the same, but the area is 100× smaller.
Understanding Pressure and Our Converter
Pressure is a fundamental concept in physics, defined as force applied perpendicular to a surface per unit area. From the air we breathe to the tyres on our cars, pressure plays a crucial role in our daily lives and across various scientific and engineering fields.
Our Pressure Converter is designed to help you quickly and accurately switch between common pressure units. Whether you're a UK driver checking your tyre pressure, a GCSE Physics student, or simply curious about the world around you, this tool makes understanding and converting pressure straightforward. We cover everything from Pascal (Pa) – the SI unit – to PSI, bar, mmHg, and more, with a focus on practical, real-world applications.
Common mistakes to avoid
- 1 bar is exactly the same as 1 atmosphere:While very close, these are distinct units. 1 atmosphere (atm) is defined as 101,325 Pa, whereas 1 bar is exactly 100,000 Pa. 1 bar is approximately 0.987 atmospheres, and 1 atmosphere is approximately 1.013 bar. Use our converter for precise values.
- My blood pressure is 120 over 80 PSI:Blood pressure is universally measured in millimetres of mercury (mmHg) by medical professionals, not PSI or any other unit. Blood pressure readings like 120/80 refer to 120 mmHg (systolic) and 80 mmHg (diastolic).
- PSI is a metric unit of pressure:PSI (Pounds per Square Inch) is an imperial unit, commonly used in the UK and US for tyre pressures, but it is not part of the metric (SI) system. PSI is an imperial unit. The metric (SI) unit for pressure is the Pascal (Pa), or its multiples like kPa (kilopascal) and MPa (megapascal).
- My car's tyre pressure should be 2.2 PSI:2.2 PSI is an extremely low pressure, far too low for a car tyre. This mistake often comes from confusing PSI with bar, where 2.2 bar is a common car tyre pressure. Car tyre pressures are typically around 30-35 PSI or 2.0-2.4 bar. Always check your vehicle's specific recommendations, usually found on a sticker inside the door jamb or fuel flap.
Questions students ask
How do I convert PSI to bar?
What pressure should my car tyres be?
What is atmospheric pressure in different units?
• 101,325 Pascals (Pa)
• 101.325 kilopascals (kPa)
• 1.01325 bar
• 1013.25 millibar (mbar) – commonly used in meteorology
• 1 atmosphere (atm)
• 14.696 Pounds per Square Inch (PSI)
• 760 millimetres of mercury (mmHg)
• 29.92 inches of mercury (inHg)