Chemistry textbooks love the atmosphere (atm) as a pressure unit — 1 atm is the average air pressure at sea level, the pressure that supports a 760-millimeter column of mercury in a barometer. But physics formulas, engineering specs, and weather instruments usually want pascals, the SI unit defined as one newton per square meter. The conversion is exact and easy to memorize: one standard atmosphere equals 101,325 pascals. Type 1 into the Atmospheres (atm) box and the Pascal (Pa) readout shows 101,325, plus the same pressure as 1.01325 bar and 14.6959 PSI at no extra charge. Try 2.5 — the neighborhood of a pressure cooker or an espresso machine portafilter — and you will see 253,312.5 Pa. Divers, HVAC technicians, and students all run into atm-to-pascal conversions, and confusing the units can be genuinely dangerous: 3 atm is not 3 pascals, it is more than 300,000 of them. Keep this page bookmarked for the moment a recipe, a gauge, or a lab manual speaks a different pressure language than the formula you are using.

With the pre-filled defaults — Atmospheres (atm) 1 — the ATM to Pascal returns Pascal (Pa) 101,325, Bar 1.01325, PSI 14.6959. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.