Pressure Converter (Pa, Bar, ATM, PSI, Torr)
Convert pressure between pascal, kilopascal, bar, atmosphere, PSI, torr and mmHg with exact conversion factors and a full all-unit reference table.
Pressure Converter — interactive calculator, computed instantly in your browser.
Pressure Units Explained: Pa, Bar, ATM, PSI and Torr
Every Pressure Unit Anchors to the Pascal
Pressure is force spread over area — pascals, the SI unit, count newtons per square metre. From car tires to weather maps to blood pressure cuffs, different fields grew different units, and confusing them is more than academic: an underinflated tire at 32 psi versus 32 kPa is a safety hazard. Convert through the pascal and every unit snaps into place.
1. The Core Units and Their Exact Factors
- Pa / kPa / MPa: scientific base — 1 kPa = 1,000 Pa, weather pressure near sea level ≈ 101.325 kPa
- Bar: exactly 100,000 Pa — meteorology and European tire gauges quote bar or mbar (hPa)
- Atmosphere: defined as exactly 101,325 Pa — the old standard of sea-level air
- PSI: 6,894.757 Pa — US tire and scuba tanks; a typical car tire reads 30–35 psi
- Torr / mmHg: exactly 1/760 of an atmosphere (133.322 Pa) — medicine, vacuum physics, and blood pressure live here
2. Which Unit Where?
Engineering drawings in the US specify psi; European weather charts use hPa (millibars); laboratories quote torr for vacuum; scuba regulators speak bar; aviation altimeters show inHg in North America and hPa elsewhere. The number itself is meaningless without its unit — and converting first prevents the classic 10×-off errors between kPa and psi ranges.
3. Worked Example and Gauge vs Absolute
- Normalize to pascals first: 1 atm × 101,325 = 101,325 Pa, then divide by the target factor
- Gauge pressure (what tires measure) starts at local atmospheric pressure; absolute pressure starts at perfect vacuum — add ≈14.7 psi (101.325 kPa) to convert gauge to absolute
- Vacuum work quotes negative gauge or absolute pressure in torr; a perfect vacuum is 0 absolute but −14.7 psi gauge
🔗 Measurement Cross-References
Pressure sits alongside every other physical unit — browse our 🔁 Conversion Hub for temperature, length, speed, and data-size tools.
Gas laws tie pressure to temperature directly, so keep the temperature converter handy below.
Frequently Asked Questions (Pressure Converter)
One pascal is the pressure of one newton acting over one square metre — a very small amount, roughly the weight of a sheet of paper resting on a table. Because it is so small, engineering uses kilopascals (1,000 Pa) or megapascals (1,000,000 Pa) for convenient magnitudes.
Both measure force over area but on different scales: 1 bar equals exactly 100,000 Pa while 1 psi equals about 6,895 Pa, so one bar is roughly 14.5 psi. European tires list bar, American tires list psi, and mixing them up underinflates a tire by about a factor of 14.5.
They are effectively identical: one torr is defined as exactly 1/760 of an atmosphere (133.322 Pa), and one millimetre of mercury is the pressure of a 1 mm mercury column (133.322 Pa at standard gravity) — they differ only in the fourth decimal place, so clinical and lab readings are interchangeable.
Multiply the atmosphere value by 101,325 pascals, then divide by 6,894.757 (the pascal value of one psi). One atmosphere works out to 14.696 psi — which is why a car tire at 32 psi gauge sits at about 46.5 psi absolute.
Gauge pressure measures against the surrounding atmosphere, so a tire gauge reads zero when off the rim; absolute pressure measures against a perfect vacuum. Absolute = gauge + atmospheric pressure (about 101.325 kPa or 14.7 psi) — always state which one a number refers to.