What is 1 atmosphere in common units?

1 atm = 101,325 Pa = 101.325 kPa = 1.01325 bar = 14.6959 PSI = 760 Torr = 1013.25 mbar.

Is Torr the same as mmHg?

Nearly identical. Both ≈ 133.322 Pa. The difference is less than 0.000015% — negligible for all practical purposes.

Why do tyres use different units in different countries?

The US uses PSI, Europe prefers bar, Australia mandates kPa. 1 bar = 14.5038 PSI = 100 kPa — all represent the same physical pressure.

What pressure unit does weather forecasting use?

Meteorology uses millibar (mbar) or hectopascal (hPa), which are numerically identical. Standard atmospheric pressure is 1013.25 mbar.

Converters

Pressure converter

Instantly convert between PSI, Bar, Pascal, Kilopascal, Atmosphere, Torr, mmHg, and Millibar. Live bidirectional conversion — type in either field and all units update instantly. Includes an all-units output panel and a real-world reference scale with common pressure benchmarks.

8 pressure units Live bidirectional All-units panel Swap units Real-world reference Copy to clipboard

Pressure Converter

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Pressure Units — A Complete Guide

Pressure is defined as force per unit area. The SI unit is the Pascal (Pa), named after Blaise Pascal, equal to one Newton per square metre. In practice, engineers and scientists use a wide range of derived units depending on their field — PSI dominates in North American industry, Bar is preferred in Europe, and Atmosphere is used for atmospheric science.

Accurate pressure conversion matters wherever precise measurements are critical: tyre inflation, hydraulic systems, weather forecasting, scuba diving, medical equipment, and industrial process control all rely on consistent pressure values.

Pressure Units Explained

Pa Pascal

The SI base unit of pressure. 1 Pa = 1 N/m². Extremely small in everyday terms — standard atmospheric pressure is about 101,325 Pa.

Used in physics, structural engineering, and acoustics.

kPa Kilopascal

1,000 Pascals. Standard atmospheric pressure ≈ 101.325 kPa. Commonly used for tyre pressure in many countries (e.g. Australia, Canada).

Tyres are often inflated to 200–260 kPa.

bar Bar

1 bar = 100,000 Pa ≈ 0.987 atm. Very close to standard atmospheric pressure. Widely used in European industry, weather, and scuba diving.

Car tyres: ~2.2–2.5 bar. Scuba tanks: ~200–300 bar.

PSI Pounds per Square Inch

1 PSI = 6,894.76 Pa. The standard pressure unit in the United States for tyres, hydraulics, and gas systems. 1 bar ≈ 14.5038 PSI.

Car tyres: ~30–35 PSI. Bicycle tyres: ~80–130 PSI.

atm Atmosphere

1 atm = 101,325 Pa exactly. Defined as standard atmospheric pressure at sea level. Used in chemistry, meteorology, and scuba depth tables.

Every 10 m underwater adds ~1 atm of pressure.

Torr Torr

1 Torr = 1/760 atm ≈ 133.322 Pa. Named after Evangelista Torricelli. Widely used in vacuum technology and low-pressure gas systems.

Used in semiconductor fabrication and mass spectrometry.

mmHg Millimetres of Mercury

1 mmHg ≈ 133.322 Pa. Essentially equal to 1 Torr. Used almost exclusively in medicine for blood pressure and intraocular pressure.

Normal blood pressure: ~120/80 mmHg.

mbar Millibar

1 mbar = 100 Pa = 0.001 bar. Standard atmospheric pressure = 1013.25 mbar. Almost exclusively used in meteorology and weather forecasting.

Hurricanes can have central pressures below 900 mbar.

Quick Conversion Reference Table

One of each unit expressed in all others (rounded to 6 significant figures):

Unit	= Pa	= kPa	= bar	= PSI	= atm	= Torr
1 Pa	1	0.001	0.00001	0.000145	9.87×10⁻⁶	0.0075
1 kPa	1,000	1	0.01	0.14504	0.009869	7.5006
1 bar	100,000	100	1	14.5038	0.986923	750.062
1 PSI	6,894.76	6.89476	0.068948	1	0.068046	51.7149
1 atm	101,325	101.325	1.01325	14.6959	1	760
1 Torr	133.322	0.133322	0.001333	0.019337	0.001316	1

Frequently Asked Questions

Absolute pressure is measured from a complete vacuum (zero pressure). Gauge pressure is measured relative to atmospheric pressure — it shows how much pressure is above or below atmospheric. Tyre pressures are typically gauge pressures. Most physics formulas use absolute pressure. This converter uses absolute pressure throughout.

1 atm = 101,325 Pa = 101.325 kPa = 1.01325 bar = 14.6959 PSI = 760 Torr = 760 mmHg = 1013.25 mbar. This is the standard reference pressure corresponding to sea-level conditions.

The US and UK use PSI. Continental Europe and international standards favour Bar or kPa. Australia mandates kPa on vehicle door stickers. Japan uses kPa. All modern pressure gauges display the same pressure — just using different scale conventions. To convert: 1 bar = 14.5038 PSI = 100 kPa.

Very nearly. The Torr is defined as exactly 1/760 of a standard atmosphere = 133.3224 Pa. The mmHg is based on the mercury column measurement and equals 133.3224 Pa under standard conditions. The two differ by less than 0.000015%, which is negligible for virtually all practical applications.

Approximately 10.33 metres (33.9 feet) of seawater adds exactly 1 atm of pressure (approximately). So at 10 m depth, the absolute pressure is about 2 atm (1 atm of water + 1 atm of atmosphere above). This is why scuba equipment is rated in "bar absolute" or "ata".

Meteorology uses the millibar (mbar) or hectopascal (hPa) — these are numerically identical: 1 hPa = 1 mbar = 100 Pa. Standard sea-level atmospheric pressure is 1013.25 mbar/hPa. Stormy weather brings lower readings; clear, high-pressure systems exceed 1020 mbar.

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