Pressure Converter
Convert between pascals, bars, PSI, atmospheres, and mmHg. Used by engineers working across metric and imperial hydraulic systems.
Pressure Converter
Enter a pressure value and select its unit β all other units update instantly.
Quick References
How to Convert Between PSI, Bar, mmHg, and Other Pressure Units
Your European car manual specifies 2.2 bar for the front tyres, but the pressure gauge at the petrol station reads PSI. Pumping to 2.2 PSI would leave the tyres dangerously flat. Enter 2.2, select bar, and the converter instantly shows 31.91 PSI, 1650 mmHg, and every other equivalent. The copy button lets you paste the PSI value straight into your mental checklist before inflating.
The converter handles 11 units from pascals to inches of water column. A nurse checking a ventilator set to 5.0 kPa needs to verify it matches the 37.5 mmHg ordered by the physician. A weather enthusiast comparing a storm reading of 985 hPa with a US forecast of 29.09 inHg can confirm they describe the same low-pressure system. The quick-reference row shows everyday pressures: a car tyre at 220 kPa, a pressure cooker at 200 kPa, a SCUBA tank at 20,684 kPa.
Automotive tyre pressure where the wrong unit means danger
A driver in the US sees their German car manual specifying 2.4 bar for rear tyres. If they pump to 2.4 PSI instead, the tyres are at about 17% of their intended pressure β a blowout risk at highway speed. The correct value is 34.8 PSI. This converter eliminates that dangerous confusion by showing all equivalent values at once, so you can match the number to the unit your gauge displays.
A patient uses a home monitor that displays kPa, but their doctor's records show mmHg. A reading of 16.0/10.7 kPa converts to 120/80 mmHg β the standard normal range. If the patient misreads the kPa value as mmHg and reports 16/10 to their doctor, the doctor would diagnose dangerously low blood pressure. The converter bridges the gap between medical device standards across countries.
A sailor in the Caribbean monitors barometric pressure and sees 1005 hPa dropping rapidly. The hurricane advisory from the US National Hurricane Centre reports central pressure in millibars (identical to hPa) but older charts use inches of mercury. Converting 950 hPa (a Category 3 hurricane) gives 28.05 inHg. Knowing both numbers means the sailor can read weather charts from any source without confusion.
Related tools
How the Pressure Converter Handles PSI, Bar, mmHg, and Kilopascals
Every unit in the converter is stored as a multiple of one pascal. When you enter 32 PSI, the tool multiplies 32 by 6894.757 to get 220,632.2 Pa, then divides by each target unit's factor. Because the conversion passes through pascals in a single step, there is no chain of intermediate conversions. The result for 32 PSI to bar is exactly 2.206322 bar β not an approximation derived from rounding 1 PSI = 0.06894757 bar first.
Why standard atmosphere is defined as exactly 101,325 Pa
The standard atmosphere (atm) was defined by the International Union of Pure and Applied Chemistry (IUPAC) as exactly 101,325 pascals. This value represents the average atmospheric pressure at sea level at 15Β°C. The bar, by contrast, is defined as exactly 100,000 Pa β a round number chosen for convenience. The difference between 1 atm and 1 bar is 1,325 Pa, or about 1.3%. This matters in aviation, where altimeter settings are calibrated in hectopascals (equivalent to millibars), and in weather forecasting, where a 1 hPa change in pressure can indicate a significant weather shift.
PSI (pound-force per square inch) is derived from the pound-force (4.4482216152605 N) divided by the square inch (6.4516 Γ 10β»β΄ mΒ²). The result is 6894.757293168... Pa. This factor has more decimal places than the others because it combines two exact definitions (the pound-force and the inch) through division, producing an irrational number that must be truncated for display. mmHg uses standard gravity (9.80665 m/sΒ²) and the density of mercury at 0Β°C (13,595.1 kg/mΒ³), giving 133.322387415 Pa.
Gauge pressure versus absolute pressure
Most pressure gauges read gauge pressure β relative to the surrounding atmosphere. A tyre gauge reading 32 PSI means 32 PSI above atmospheric pressure, which is 46.7 PSI absolute (32 + 14.696). Weather reports use absolute pressure. A barometric reading of 1013 hPa is absolute. If you subtract atmospheric pressure (1013 hPa), you get 0 hPa gauge β which is just ambient air. This converter works with absolute pressure units. To convert gauge to absolute, add 14.696 PSI (or 101.325 kPa) first.
Water column units (cmHβO, inHβO) are used for low-pressure measurements like ventilation systems and medical ventilators. 1 cmHβO = 98.0665 Pa. A typical medical ventilator operates at 5-20 cmHβO, which is 490-1961 Pa β far below atmospheric pressure. These units exist because mercury is too dense to measure such small pressures accurately; water provides a more readable column height.
Frequently Asked Questions
How many PSI is 2.4 bar?
2.4 bar equals 34.81 PSI. The conversion factor is 1 bar = 14.50377 PSI. For a quick mental estimate, multiply bar by 14.5 β so 2.4 Γ 14.5 = 34.8 PSI. This is the standard front tyre pressure for most European sedans. If your gauge reads PSI, set it to about 35.
What is the difference between PSI and kPa?
1 PSI equals 6.89476 kPa. PSI is pounds per square inch (imperial), while kPa is kilopascals (metric). A car tyre at 32 PSI is at 220.6 kPa. For quick estimates, multiply PSI by 6.9 to get kPa. The kPa figure is what European car manuals and weather reports use.
Why do doctors still use mmHg for blood pressure?
Blood pressure was historically measured by the height of a mercury column in a sphygmomanometer. A reading of 120/80 mmHg means the blood pressure supports a column of mercury 120 mm high during systole. Although mercury devices are being phased out for environmental reasons, the mmHg unit persists because every doctor and nurse trained worldwide understands it. Electronic monitors convert their sensor readings to mmHg for display.
How do I convert inches of mercury to hPa?
Multiply inHg by 33.8639 to get hPa. A standard sea-level reading of 29.92 inHg equals 1013.25 hPa. For quick estimates, multiply inHg by about 33.9. US weather reports use inHg, while international reports use hPa (identical to mbar). The conversion matters when comparing hurricane forecasts from the US National Hurricane Centre (inHg) with international models (hPa).
What happens to tyre pressure in cold weather?
Tyre pressure drops about 1 PSI for every 10Β°F (5.5Β°C) decrease in ambient temperature. A tyre inflated to 32 PSI in summer at 80Β°F would read about 28 PSI on a 40Β°F winter morning β below the recommended minimum. This is why tyre pressure warning lights often activate during autumn temperature drops. Check and adjust pressure when tyres are cold.