Pressure Converter

Q: How does altitude affect atmospheric pressure?

Atmospheric pressure decreases with altitude because there is less air mass above you. At sea level: ~101,325 Pa (1 atm, 14.7 psi). At Denver, CO (5,280 ft / 1,609 m): ~83,000 Pa (0.82 atm). At the top of Mount Everest (8,849 m): ~33,700 Pa (0.33 atm). This lower pressure at altitude means water boils at lower temperatures (about 90°C at 3,000 m vs 100°C at sea level), affects engine performance, and requires supplemental oxygen above ~8,000 m.

Q: What is the difference between absolute and gauge pressure?

Absolute pressure is measured relative to a perfect vacuum (zero pressure). Gauge pressure is measured relative to the current atmospheric pressure. Most everyday pressure measurements (tire pressure, blood pressure, compressed air) are gauge pressure — they tell you how much above atmospheric pressure something is. A tire listed at 35 PSI gauge is actually 35 + 14.7 = 49.7 PSI absolute. In scientific and industrial contexts, absolute pressure is often used to avoid ambiguity caused by varying atmospheric pressure with altitude.

Q: Why do weathermen use hectopascals (hPa) for air pressure?

Weather forecasts use hectopascals (hPa) where 1 hPa = 100 Pa. This is numerically identical to millibar (mbar), a unit meteorologists used for decades — so switching to hPa preserved familiar numerical values (standard atmospheric pressure remains ~1,013 hPa or mbar). Weather maps show isobars (lines of equal pressure) in hPa; high pressure systems are ~1020–1030 hPa and indicate calm weather, while low pressure systems below ~1000 hPa often bring storms. Hurricanes can reach 870–900 hPa at their center.

Convert pressure between pascals, psi, bar, atmospheres, mmHg, and more.

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Converted Pressure

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How it works

Pressure is force distributed over an area, and almost every field that measures it has settled on its own preferred unit. Tire inflation is quoted in PSI in the US and in bar across Europe, blood pressure is read in millimeters of mercury, weather reports use hectopascals or millibars, and heavy industry often works in bar or megapascals. A pressure converter lets you move between all of these without memorising dozens of separate relationships. The SI unit is the pascal (Pa), defined as one newton per square meter. One standard atmosphere equals 101,325 Pa, the average air pressure at sea level, while one bar is 100,000 Pa — very slightly below an atmosphere. PSI remains entrenched in the US for tires, hydraulics, and compressed air; a typical car tire sits at 32 to 35 PSI, or 2.2 to 2.4 bar. Because each unit carries a fixed ratio to the pascal, this pressure converter normalises the input to pascals first and then scales to the chosen output, keeping conversions like PSI to bar or mmHg to kilopascals exact. Engineers, divers, medical staff, meteorologists, and mechanics all rely on a pressure converter to communicate safely across measurement systems.

Formula

Convert to pascals (SI base unit) then to target unit

Pressure conversion holds because every pressure unit equals a fixed number of pascals, the SI unit for pressure (one newton per square meter). The converter multiplies the input by its pascal ratio to reach the common base, then divides by the target's ratio to scale out, so results stay exact. Key ratios: 1 psi = 6,894.76 Pa, 1 bar = 100,000 Pa, 1 atm = 101,325 Pa, and 1 mmHg = 133.322 Pa.

Source:International System of Units (SI) — NIST

We review all our tools from time to time to ensure accuracy.

Worked example

Value:32From:psiTo:bar

32 PSI (typical tire pressure) = 2.206 bar. In European countries, tire pressure is listed in bar, so a tire inflated to 32 PSI in the US should be inflated to 2.2 bar in Europe.

How to use this calculator

1
Enter your values
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2
Adjust the options
Fine-tune any options to match your situation.
3
Read your result
Converted Pressure updates instantly as you type — no button to press.

Frequently asked questions

What is the difference between psi and bar?

PSI (pounds per square inch) and bar are both common pressure units. 1 bar = 14.5038 psi, and 1 psi = 0.0689476 bar. Bar is widely used in Europe and internationally; PSI dominates in the US. For tire pressure: US cars show 30–35 PSI; European cars show 2.0–2.4 bar. For scuba diving: a full tank is 200–300 bar (2,900–4,350 PSI). For espresso machines: standard extraction pressure is 9 bar (130 PSI).

What is blood pressure measured in mmHg?

Blood pressure is measured in millimeters of mercury (mmHg) — a historical unit from when sphygmomanometers used actual mercury columns. Normal blood pressure is below 120/80 mmHg. In SI units, 1 mmHg = 133.322 pascals. The two numbers in blood pressure are systolic (peak pressure when heart contracts, normal < 120 mmHg) and diastolic (resting pressure between beats, normal < 80 mmHg). Despite the SI unit being kPa, mmHg remains universal in medicine for blood pressure.

How does altitude affect atmospheric pressure?

Atmospheric pressure decreases with altitude because there is less air mass above you. At sea level: ~101,325 Pa (1 atm, 14.7 psi). At Denver, CO (5,280 ft / 1,609 m): ~83,000 Pa (0.82 atm). At the top of Mount Everest (8,849 m): ~33,700 Pa (0.33 atm). This lower pressure at altitude means water boils at lower temperatures (about 90°C at 3,000 m vs 100°C at sea level), affects engine performance, and requires supplemental oxygen above ~8,000 m.

What is the difference between absolute and gauge pressure?

Absolute pressure is measured relative to a perfect vacuum (zero pressure). Gauge pressure is measured relative to the current atmospheric pressure. Most everyday pressure measurements (tire pressure, blood pressure, compressed air) are gauge pressure — they tell you how much above atmospheric pressure something is. A tire listed at 35 PSI gauge is actually 35 + 14.7 = 49.7 PSI absolute. In scientific and industrial contexts, absolute pressure is often used to avoid ambiguity caused by varying atmospheric pressure with altitude.

Why do weathermen use hectopascals (hPa) for air pressure?

Weather forecasts use hectopascals (hPa) where 1 hPa = 100 Pa. This is numerically identical to millibar (mbar), a unit meteorologists used for decades — so switching to hPa preserved familiar numerical values (standard atmospheric pressure remains ~1,013 hPa or mbar). Weather maps show isobars (lines of equal pressure) in hPa; high pressure systems are ~1020–1030 hPa and indicate calm weather, while low pressure systems below ~1000 hPa often bring storms. Hurricanes can reach 870–900 hPa at their center.