How It Works
This converter uses the pascal (Pa) as its base unit — the SI unit of pressure equal to one newton per square meter. Each pressure unit has a known factor relative to the pascal. The tool converts by multiplying your input by the source unit’s pascal-equivalent factor, then dividing by the target unit’s factor, all with BigNumber precision.
Example Problem
Convert 2 atmospheres (atm) to pounds per square inch (psi).
- 1 atm = 14.696 psi.
- 2 × 14.696 = 29.392 psi.
Key Concepts
Pressure is force per unit area, with the pascal (1 N/m²) as the SI base unit. Common units include atmospheres (atm), bar, psi, torr, and mmHg. Many units have historical origins: mmHg from mercury manometers, atm from sea-level air pressure, and psi from imperial engineering practice.
Applications
- Meteorology: converting between millibars, hectopascals, and inches of mercury for weather reporting
- Tire maintenance: translating between psi, bar, and kPa for international tire pressure specifications
- Vacuum science: converting between torr, pascal, and millibar for laboratory vacuum system gauges
- Scuba diving: calculating depth pressure in atmospheres, bar, or psi for dive planning
Common Mistakes
- Confusing gauge pressure and absolute pressure — gauge reads zero at atmospheric pressure, absolute reads zero at perfect vacuum; add 14.696 psi (1 atm) to convert gauge to absolute
- Treating bar and atm as identical — 1 bar = 100,000 Pa vs 1 atm = 101,325 Pa, a 1.3% difference that matters in precision work
- Using mmHg and torr interchangeably for high-precision work — they differ by about 0.000015%, negligible for most purposes but significant in metrology
Frequently Asked Questions
How many psi are in one atmosphere?
One standard atmosphere (atm) equals approximately 14.696 psi (pounds per square inch). Standard atmospheric pressure is defined as exactly 101,325 pascals.
What is the difference between bar and atm?
One bar equals 100,000 pascals, while one atmosphere equals 101,325 pascals. They are close in magnitude (1 atm ≈ 1.01325 bar), but bar is a metric unit while atm is a physical reference based on sea-level air pressure.
What is a torr?
A torr is approximately equal to 1 mmHg (millimeter of mercury) and is defined as 1/760 of a standard atmosphere, or about 133.322 pascals. It is commonly used in vacuum science and laboratory settings.
