Pressure Converter

What Is Pressure?

Pressure is force applied per unit area. When you press your thumb against a table, the pressure depends on both how hard you push and the area of contact. The same force concentrated on a smaller area creates higher pressure, which is why needles pierce skin and snowshoes prevent sinking. Pressure is measured in various units depending on the application: pascals (Pa) in science, PSI in US engineering, bar in European engineering, atmospheres in chemistry, and mmHg (torr) in medicine. Enter any pressure value in the converter above to translate between all common units.

Common Pressure Unit Conversions

1 atmosphere (atm) = 101,325 pascals (Pa) = 101.325 kilopascals (kPa) = 14.696 PSI = 1.01325 bar = 760 mmHg (torr) = 29.92 inHg. 1 PSI = 6,895 Pa = 6.895 kPa = 0.0689 bar = 51.71 mmHg. 1 bar = 100,000 Pa = 14.504 PSI = 0.9869 atm = 750.06 mmHg. These conversions are essential when reading specifications from different countries, interpreting scientific data, or working with equipment rated in unfamiliar units.

Tire Pressure: PSI and Bar

Tire pressure is the most common everyday pressure measurement. US tire gauges read in PSI (pounds per square inch). European gauges read in bar or kPa. A typical passenger car tire is inflated to 32-35 PSI (2.2-2.4 bar, 220-240 kPa). Bicycle tires range from 30 PSI (mountain bike) to 120 PSI (road bike). Truck tires run 80-100 PSI. Under-inflated tires waste fuel, wear unevenly, and risk blowouts. Over-inflated tires reduce traction and produce a harsh ride. Check the sticker inside your driver's door for the recommended pressure, and use the converter above to translate between PSI and bar if your gauge uses a different unit than the specification.

Atmospheric Pressure and Weather

Standard atmospheric pressure at sea level is 1 atm = 1013.25 hPa (hectopascals, also called millibars). Weather forecasts report pressure in hPa, mmHg (inHg in the US), or millibars. High pressure (above 1013 hPa) generally brings clear skies. Low pressure (below 1013 hPa) often brings clouds and precipitation. Pressure drops approximately 12 hPa per 100 meters of altitude gain, which is why aircraft cabins are pressurized and why cooking times change at high altitudes. Mount Everest's summit pressure is about 337 hPa (one-third of sea level), making breathing without supplemental oxygen nearly impossible.

Blood Pressure: mmHg

Medical blood pressure readings use millimeters of mercury (mmHg), a unit dating back to mercury column manometers. A healthy reading is around 120/80 mmHg (systolic/diastolic). High blood pressure (hypertension) is defined as consistently above 130/80 mmHg. The unit mmHg equals exactly 1 torr, named after Evangelista Torricelli who invented the barometer. While most industries have moved to SI units, medicine retains mmHg for blood pressure because decades of clinical guidelines, research data, and physician training reference this unit. Converting: 120 mmHg = 16 kPa = 2.32 PSI.

Industrial Pressure: Gauge vs Absolute

Gauge pressure measures relative to atmospheric pressure: a tire gauge reading 32 PSI means 32 PSI above atmospheric pressure. Absolute pressure measures relative to vacuum: the same tire has an absolute pressure of 32 + 14.7 = 46.7 PSIA (PSI absolute). The distinction matters in engineering calculations involving gas laws (PV = nRT uses absolute pressure), vacuum systems, and altitude-dependent applications. Gauges typically measure gauge pressure (PSIG), while scientific calculations require absolute pressure (PSIA). The converter above defaults to gauge pressure for practical applications.

Pressure in Cooking and Diving

Pressure cookers typically operate at 15 PSI above atmospheric (about 2 atm total), which raises the boiling point of water to approximately 121 degrees Celsius. This higher temperature cooks food 30-70% faster than conventional methods. Scuba diving pressure increases by 1 atm for every 10 meters of depth: at 30 meters, total pressure is 4 atm. Divers must ascend slowly to prevent decompression sickness (the bends) caused by dissolved nitrogen forming bubbles as pressure drops. Both applications demonstrate how pressure affects physical and chemical processes in practical, everyday contexts.

Vacuum Measurement

Vacuum is pressure below atmospheric. A perfect vacuum (0 absolute pressure) is practically unachievable. Industrial vacuum levels are measured in torr, millibar, or as a percentage of atmospheric pressure. A typical vacuum cleaner creates about 80 kPa absolute (20 kPa below atmospheric). Laboratory vacuum pumps achieve below 0.001 torr. Space is not a perfect vacuum but contains about 1-10 particles per cubic centimeter in interstellar regions, compared to about 2.5 times 10^19 particles per cubic centimeter in Earth's atmosphere at sea level.

Frequently asked questions