What is 1 atm in psi?
1 standard atmosphere equals 14.6959 psi (or 101.325 kPa, or 1.01325 bar).
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Pressure converter
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Pressure is force per unit area. The SI unit is the pascal (Pa), equal to 1 newton per square meter. Common pressure units include the kilopascal (kPa), bar (100,000 Pa), atmosphere (101,325 Pa exact), psi (6,894.76 Pa), mmHg (133.322 Pa), and torr (essentially the same as mmHg). 1 standard atmosphere equals 14.6959 psi or 1.01325 bar.
Example pressure conversions
1 atm101,325 Pa, 1.01325 bar, 14.6959 psi (exact)
1 bar100,000 Pa (exact), 14.5038 psi, 750.062 mmHg
1 psi6,894.76 Pa, 0.068948 bar
1 kPa1,000 Pa, 0.145038 psi
Open the live pressure converter for any input value.
Common pressure units across industries
Different industries chose different pressure units and never coordinated. Weather forecasting uses millibars (now called hectopascals in scientific contexts) for atmospheric pressure. Tire pressure uses psi in the US and bar or kPa in metric countries. Medicine uses mmHg for blood pressure (a holdover from mercury manometers). Vacuum work uses torr for low pressures. HVAC uses inches of water column for duct pressure.
The pascal is the SI coherent unit but is rarely seen in everyday work because it's a small unit: atmospheric pressure at sea level is about 101,325 Pa, which is why we usually quote 101.325 kPa or 1.01325 bar instead.
Gauge vs absolute pressure
Pressure measurements come in two flavors. Absolute pressure is referenced to a perfect vacuum: an absolute reading of zero would mean no gas pressure at all. Gauge pressure is referenced to atmospheric pressure: a tire pressure gauge reading 32 psi means 32 psi above atmospheric, or about 46.7 psi absolute. The 'a' or 'g' suffix (psia, psig) makes this explicit; without a suffix, context determines which is meant.
Weather pressure is reported as absolute. Tire and engine pressures are gauge. Industrial process control uses both, depending on the variable. Mixing the two by accident is one of the most common sources of pressure-conversion errors.
Reference pressures worth knowing
Standard atmospheric pressure at sea level is exactly 101,325 Pa by definition (since 1954). That equals 1 atm, 1.01325 bar, 1013.25 hPa, 14.6959 psi, 760 mmHg, and 760 torr. Weather low-pressure systems run around 950-990 hPa; highs run 1020-1040 hPa.
Typical car tire pressure is 30-35 psi (207-241 kPa or 2.07-2.41 bar). Healthy human blood pressure is 120/80 mmHg (about 16/10.7 kPa). Underwater pressure increases by about 1 atm per 10 meters of seawater depth. Industrial high-pressure water-jet cutting uses 60,000-90,000 psi (414-621 MPa).
Common pressure conversions
| From | Equivalent |
|---|---|
| 1 atm | 101,325 Pa, 1.01325 bar, 14.6959 psi (exact) |
| 1 bar | 100,000 Pa (exact), 14.5038 psi, 750.062 mmHg |
| 1 psi | 6,894.76 Pa, 0.068948 bar |
| 1 kPa | 1,000 Pa, 0.145038 psi |
| 1 MPa | 10 bar, 145.038 psi |
| 1 mmHg | 133.322 Pa, 0.0193368 psi |
| 1 torr | 133.322 Pa (= 1 mmHg) |
| 1 inch Hg | 3,386.39 Pa, 0.491154 psi |
| 1 hPa (= 1 mbar) | 100 Pa |
Frequently asked questions
Why is psi used for tire pressure but bar for European cars?
Customary inertia. The US adopted psi (pound-force per square inch) and never switched. Metric countries chose bar because it's close to 1 atm and easier to communicate than 100 kPa.
What's the difference between psi and psig?
psig is psi gauge (relative to atmospheric pressure). psia is psi absolute (relative to vacuum). A tire gauge reading 32 psi is gauge pressure (psig); add about 14.7 psi to get absolute (~46.7 psia).
Are torr and mmHg the same?
Functionally yes. 1 torr is defined as exactly 1/760 of a standard atmosphere, which works out to 133.322 Pa. 1 mmHg as defined in vacuum work is also 133.322 Pa. The two are interchangeable to the precision most uses require.
What is normal blood pressure in pascals?
Healthy 120/80 mmHg equals 15.999/10.666 kPa, or 16/10.7 kPa rounded. Blood-pressure cuffs always report mmHg because that's the medical convention.