Conversion Reference Table
| Unit | Symbol | Equivalent |
|---|---|---|
| Pascal (Pa) | Pa | SI base unit of pressure |
| Kilopascal (kPa) | kPa | 1 kPa = 1,000 Pa |
| Megapascal (MPa) | MPa | 1 MPa = 1,000,000 Pa |
| Bar | bar | 1 bar = 100,000 Pa |
| Atmosphere (atm) | atm | 1 atm = 101,325 Pa (sea level) |
| PSI | psi | 1 psi = 6,894.757 Pa |
| mmHg (Torr) | mmHg | 1 mmHg = 133.322 Pa |
| Inches Hg | inHg | 1 inHg = 3,386.389 Pa |
| cm H₂O | cmH2O | 1 cmH₂O = 98.0665 Pa |
Frequently Asked Questions
What is 1 atmosphere in PSI?
Standard atmospheric pressure (1 atm) equals 14.696 psi. This is the average air pressure at sea level and is the reference point for gauge pressure measurements. Tire pressure gauges measure in psi above atmospheric pressure (gauge pressure).
What is the difference between absolute and gauge pressure?
Absolute pressure is measured from perfect vacuum (0 Pa). Gauge pressure is measured relative to atmospheric pressure — so 0 psi gauge = 14.696 psi absolute. Tire pressure, blood pressure cuff readings, and most industrial gauges report gauge pressure.
What is blood pressure in SI units?
A typical blood pressure of 120/80 mmHg equals about 15,998/10,666 Pa or 16.0/10.7 kPa. Medical devices traditionally use mmHg; the WHO recommends kPa but mmHg remains dominant in clinical practice.
What pressure unit is used in weather forecasting?
Weather uses hectopascals (hPa), which equal millibars (mbar). Standard sea-level pressure is 1013.25 hPa. Low pressure systems (below ~1000 hPa) typically bring storms; high pressure (above ~1020 hPa) brings clear weather.