Staring at a European tire gauge that reads in bar while your car's door sticker lists PSI is a rite of passage for international drivers — and the same clash shows up on espresso machines, scuba regulators, and bicycle pumps sold outside the United States. The bar is a metric pressure unit equal to exactly 100,000 pascals, roughly one atmosphere, and it is the default wherever the metric system rules. PSI, pounds per square inch, is what American gauges display. The bridge between them is 14.5038: multiply bar by it to get PSI. Type 2.3 into the Bar box — a common car tire pressure — and the PSI (lb/in²) readout shows about 33.36. An espresso machine pulling a 9-bar shot is running near 130.5 PSI, which explains why those little seals are so heavily built. You also get pascals (bar × 100,000) and atmospheres (bar ÷ 1.01325) as bonus readouts. Because bar and PSI sit in similar everyday ranges, people mix them up constantly — remembering "bar times fourteen and a half" keeps tires, shots, and tanks safe.

With the pre-filled defaults — Bar 1 — the Bar to PSI returns PSI (lb/in²) 14.5038, Pascal (Pa) 100,000, Atmospheres (atm) 0.986923. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.