A pressure converter translates between PSI, bar, kilopascals, atmospheres, and millimeters of mercury. Pressure conversions are used in tire inflation, weather reports, HVAC, hydraulics, and blood pressure readings.
Pressure Converter
Pressure Reference Values
| Application | PSI | bar | kPa |
|---|---|---|---|
| Standard atmospheric pressure (1 atm) | 14.696 | 1.013 | 101.3 |
| Car tire (recommended, gauge) | 32-35 | 2.2-2.4 | 221-241 |
| Blood pressure systolic (120 mmHg) | 2.32 | 0.160 | 16.0 |
| Home water supply pressure | 40-80 | 2.76-5.52 | 276-552 |
| Hydraulic system (typical) | 100-3000 | 6.9-207 | 690-20684 |
How to Convert Pressure Units
Pressure unit conversion is needed in automotive, meteorological, medical, and engineering applications. The SI unit is the Pascal (Pa), but practical applications use kPa, bar, or PSI depending on the field.
Step 1: Key Conversion Factors
1 atm = 101,325 Pa = 101.325 kPa = 1.01325 bar = 14.696 PSI = 760 mmHg = 29.9213 inHg. For tire pressure: 1 bar ≈ 14.5 PSI, so 2.5 bar ≈ 36 PSI. For weather: standard sea-level pressure is 1013.25 hPa (hectopascals) or 1013.25 mbar — identical numerical value since 1 hPa = 1 mbar.
Step 2: Gauge vs Absolute Pressure
Tire pressure gauges read gauge pressure (above atmospheric). A tire reading 35 PSI gauge has 35 + 14.7 = 49.7 PSI absolute pressure. Weather barometers read absolute pressure. Blood pressure meters read gauge pressure in mmHg (120/80 mmHg gauge — absolute would add atmospheric pressure but this is not clinically meaningful).
Step 3: Practical Applications
Tire pressure specifications are given in gauge PSI or bar — check your door jamb sticker. Blood pressure is always in mmHg. Weather pressure is in hPa or inHg. HVAC and hydraulic systems use PSI (US) or bar (metric). Industrial specifications often use kPa or MPa for precision.
FAQ
How do I convert PSI to bar?
Multiply PSI by 0.0689476 to get bar. Example: 14.7 PSI × 0.0689476 = 1.013 bar (standard atmospheric pressure). Going the other way: multiply bar by 14.5038 to get PSI. Quick approximation: 1 bar ≈ 14.5 PSI.
What is 1 atmosphere (atm) in PSI?
Standard atmospheric pressure (1 atm) equals 14.696 PSI = 101,325 Pa = 1.01325 bar = 760 mmHg. This is the average air pressure at sea level. Tire pressure is measured in gauge PSI (above atmospheric), so a tire at 35 PSI gauge is actually 35 + 14.7 = 49.7 PSI absolute pressure.
What is normal blood pressure in kPa?
Normal blood pressure of 120/80 mmHg converts to approximately 16.0/10.7 kPa. Blood pressure is traditionally measured in mmHg (millimeters of mercury). 1 mmHg = 0.133322 kPa. Hypertension is typically defined as above 140/90 mmHg (18.7/12.0 kPa).
What is the difference between gauge pressure and absolute pressure?
Absolute pressure is measured from a perfect vacuum (0 pressure). Gauge pressure is measured relative to atmospheric pressure. A tire gauge reads gauge pressure — 35 PSI on a tire gauge means 35 PSI above atmospheric (about 50 PSI absolute). Most engineering specs use gauge pressure (PSIG) while calculations may need absolute pressure (PSIA).
Is this pressure converter free?
Yes, completely free with no signup required. All conversions run instantly in your browser.