Pressure Converters 8
Pressure is the unit most likely to kill you. Six units are in common use — pascal, bar, psi, atmosphere, kPa, mmHg (Torr) — and converting between them under time pressure has caused blowouts, cabin depressurizations, and the worst oil spill in US history. These 8 converters use exact constants. Triple-check your work.
Read the Pressure Conversion Guide
Every pressure unit — pascal, bar, psi, atm, torr — their origins and exact conversions. Deepwater Horizon, SCUBA cascade failures, Apollo 1, and why pressure errors are among the most dangerous in engineering.
Open the full guide →Pressure: The Unit Most Likely to Kill You
Pressure conversion errors have killed more people than any other unit mistake in engineering history. The Deepwater Horizon blowout (2010, 11 fatalities) involved a cascade of pressure interpretation failures — the crew misinterpreted a negative-pressure test, failed to recognize a kick in the wellbore, and methane gas reached the surface at explosive concentrations. The Apollo 1 fire (1967, 3 astronauts) was exacerbated by a pure-oxygen atmosphere at 16.7 psi above ambient — a pressure decision made without fully understanding the combustion kinetics of materials in a 100% O₂ environment. SCUBA diving deaths routinely trace back to divers confusing bar, atm, and psi when planning decompression stops.
Pressure units proliferate because different industries inherited different conventions: automotive uses psi (pounds per square inch) and bar; meteorology uses millibar and hectopascal; medicine uses mmHg (millimeters of mercury) for blood pressure; vacuum science uses torr; industrial hydraulics uses MPa. Every one of these has a precise definition that traces back to the pascal (1 Pa = 1 N/m²), the SI base unit.
Pressure Unit Reference
1 bar = 100,000 Pa (not SI, but accepted — approximately 1 atmosphere)
1 atm = 101,325 Pa (standard atmospheric pressure at sea level)
1 psi = 6,894.757293168 Pa (1 pound-force per square inch)
1 torr = 133.322368421 Pa (1/760 atm, named after Evangelista Torricelli)
1 mmHg = 133.322387415 Pa (slightly different from 1 torr due to temperature corrections)
For the engineering stories behind these numbers — Deepwater Horizon, Apollo 1, and SCUBA cascade failures — read the Pressure Conversion Guide.
Pressure in Everyday Life — The Numbers You Already Know
Most people interact with at least four pressure scales daily without recognizing them as conversions. A car tyre at 32 psi (2.2 bar, 220 kPa). A blood pressure reading of 120/80 mmHg (16.0/10.7 kPa). A weather forecast of 1,013 millibar (101.3 kPa, 1 atm). A soda can at 2-3 atm of internal pressure. A SCUBA tank at 200 bar (2,900 psi, 20 MPa). Every one of these numbers crosses a unit boundary when it moves between the device that measures it and the person who reads it.
The automobile tyre is the most common pressure translation failure. European cars specify tyre pressure in bar; US pumps read in psi; Japanese and Korean cars use kPa. A driver inflating a European-spec tyre to "32" on a US pump (thinking bar) puts in 32 psi instead of 2.2 bar — the tyre is at 32 psi instead of 32 psi? No: 2.2 bar = 32 psi. The numbers happen to coincide for one common pressure — and that coincidence has prevented thousands of blowouts while simultaneously masking how dangerous the bar/psi confusion could be at higher pressures. A truck tyre at 8 bar (116 psi) inflated to "8 psi" by a confused operator is dangerously underinflated. At 8 bar × 14.5 = 116 psi, the numbers no longer accidentally align.
Industrial Hydraulics: MPa, Bar, and the 10× Error
1 MPa = 10 bar = 145.038 psi — the hydraulic engineer's triple-scale reference
Common hydraulic system pressures: 21 MPa (210 bar, 3,045 psi) — typical excavator
Aircraft hydraulic system: 20.7 MPa (207 bar, 3,000 psi) — Boeing 737 primary system
Water jet cutter: 415 MPa (4,150 bar, 60,000 psi) — cuts steel with water and garnet
Hydraulic systems are designed in MPa, built with bar-rated components, and tested with psi-gauged equipment. The factor-of-10 relationship between MPa and bar (1 MPa = 10 bar exactly) is the one pressure conversion that never causes errors — it's a decimal shift. But the MPa-to-psi step (× 145.038) is the one that does: a hydraulic hose rated for 21 MPa (3,045 psi) connected to a system that momentarily spikes to 25 MPa (3,626 psi) sees a 19% overpressure — and the hose label, printed in MPa, won't warn the psi-reading technician.