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Pressure Unit Conversions: Complete Reference

Pressure conversion is essential in engineering, meteorology, medicine, and everyday applications like tire inflation and weather forecasting. With so many pressure units in use — pascals, bar, PSI, atmospheres, mmHg, torr, and more — converting between them can be challenging. This complete reference guide covers all major pressure units, their conversion formulas, and practical examples to help you navigate pressure conversions with confidence.

Understanding Pressure and Its Units

Pressure is defined as force per unit area. The SI unit of pressure is the pascal (Pa), which equals one newton per square meter (N/m²). Because one pascal is a very small amount of pressure, most practical applications use kilopascals (kPa), megapascals (MPa), or bar instead. The imperial system uses pounds per square inch (PSI), while meteorology often uses hectopascals (hPa) or millibars (mbar).

Common Pressure Units

Pascal (Pa): The SI unit. 1 Pa = 1 N/m². Very small; often used as kPa or MPa.
Kilopascal (kPa): 1 kPa = 1,000 Pa. Common in engineering and meteorology.
Megapascal (MPa): 1 MPa = 1,000,000 Pa. Used for high-pressure applications.
Bar: 1 bar = 100,000 Pa. Widely used in Europe. Close to 1 atmosphere.
Millibar (mbar): 1 mbar = 100 Pa = 0.001 bar. Used in meteorology.
PSI (pounds per square inch): 1 PSI = 6,894.76 Pa. Standard in the US for tire pressure and industrial applications.
Atmosphere (atm): 1 atm = 101,325 Pa. Based on standard atmospheric pressure at sea level.
mmHg (millimeters of mercury): 1 mmHg = 133.322 Pa. Used in medicine (blood pressure) and vacuum systems.
Torr: 1 Torr = 133.322 Pa. Nearly identical to mmHg. Named after Evangelista Torricelli.
Inches of mercury (inHg): 1 inHg = 3,386.39 Pa. Used in US aviation and weather.

Key Conversion Factors

Here are the most important pressure conversion factors, all relative to 1 atmosphere for easy reference:

Unit	Value at 1 atm	Conversion to Pa
1 atm	1	101,325 Pa
1 bar	0.986923 atm	100,000 Pa
1 kPa	0.009869 atm	1,000 Pa
1 MPa	9.86923 atm	1,000,000 Pa
1 PSI	0.068046 atm	6,894.76 Pa
1 mmHg	0.001316 atm	133.322 Pa
1 Torr	0.001316 atm	133.322 Pa
1 inHg	0.033421 atm	3,386.39 Pa
1 mbar	0.000987 atm	100 Pa
1 hPa	0.000987 atm	100 Pa

Common Pressure Conversions

PSI to kPa

To convert PSI to kilopascals, multiply by 6.89476:

kPa = PSI × 6.89476

Examples:

32 PSI (car tire) = 32 × 6.89476 = 220.63 kPa
35 PSI = 35 × 6.89476 = 241.32 kPa
100 PSI = 100 × 6.89476 = 689.48 kPa

kPa to PSI

To convert kilopascals to PSI, multiply by 0.145038:

PSI = kPa × 0.145038

220 kPa = 220 × 0.145038 = 31.91 PSI
250 kPa = 250 × 0.145038 = 36.26 PSI
700 kPa = 700 × 0.145038 = 101.53 PSI

Bar to PSI

To convert bar to PSI, multiply by 14.5038:

PSI = bar × 14.5038

2 bar = 2 × 14.5038 = 29.01 PSI
2.3 bar (car tire) = 2.3 × 14.5038 = 33.36 PSI
10 bar = 10 × 14.5038 = 145.04 PSI

PSI to Bar

To convert PSI to bar, multiply by 0.0689476:

bar = PSI × 0.0689476

33 PSI = 33 × 0.0689476 = 2.28 bar
50 PSI = 50 × 0.0689476 = 3.45 bar
100 PSI = 100 × 0.0689476 = 6.89 bar

Atmospheres to PSI

To convert atm to PSI, multiply by 14.6959:

PSI = atm × 14.6959

1 atm = 14.70 PSI
2 atm = 29.39 PSI
3 atm = 44.09 PSI

mmHg to kPa

To convert mmHg to kPa, multiply by 0.133322:

kPa = mmHg × 0.133322

120 mmHg (systolic blood pressure) = 120 × 0.133322 = 16.00 kPa
760 mmHg (standard atmosphere) = 760 × 0.133322 = 101.32 kPa

Comprehensive Pressure Conversion Chart

Pa	kPa	bar	PSI	atm	mmHg	inHg
100	0.1	0.001	0.0145	0.000987	0.750	0.0295
1,000	1	0.01	0.145	0.00987	7.501	0.2953
10,000	10	0.1	1.450	0.0987	75.01	2.953
50,000	50	0.5	7.252	0.493	375.03	14.764
100,000	100	1.0	14.504	0.987	750.06	29.530
101,325	101.325	1.01325	14.696	1.000	760.00	29.921
200,000	200	2.0	29.008	1.974	1,500.12	59.060
500,000	500	5.0	72.519	4.935	3,750.31	147.649
1,000,000	1,000	10.0	145.038	9.869	7,500.62	295.299
10,000,000	10,000	100.0	1,450.378	98.692	75,006.17	2,952.988

Real-World Pressure Values

To put these numbers in context, here are common pressure values encountered in everyday life and various industries:

Application	Pressure	In Other Units
Vacuum (outer space)	~0 Pa	0 atm, 0 bar
Soft vacuum	~1,000 Pa	0.01 bar, 0.145 PSI
Bike tire (road)	~600,000 Pa	6 bar, 87 PSI
Car tire	~220,000 Pa	2.2 bar, 32 PSI
Bicycle tire (mountain)	~250,000 Pa	2.5 bar, 36 PSI
Standard atmosphere	101,325 Pa	1.013 bar, 14.7 PSI
Blood pressure (systolic)	~16,000 Pa	120 mmHg
Blood pressure (diastolic)	~11,000 Pa	80 mmHg
Water pressure (10m depth)	~200,000 Pa	2 bar, 29 PSI
Scuba tank (full)	~20,000,000 Pa	200 bar, 2,900 PSI
Pressure washer	~10,000,000 Pa	100 bar, 1,450 PSI
Hydraulic system	~30,000,000 Pa	300 bar, 4,351 PSI
Deep ocean (Mariana Trench)	~110,000,000 Pa	1,100 bar, 15,954 PSI

Meteorological Pressure Conversions

Weather forecasting relies heavily on atmospheric pressure measurements. Different regions use different units:

Europe and most of the world: hectopascals (hPa) or millibars (mbar) — these are equivalent (1 hPa = 1 mbar)
United States: inches of mercury (inHg)
Some aviation contexts: millibars (mbar)

Standard sea-level pressure is 1013.25 hPa = 1013.25 mbar = 29.92 inHg = 1013.25 Pa × 100 = 101,325 Pa = 1 atm.

Weather Condition	hPa/mbar	inHg	atm
Very low pressure (storm)	950	28.05	0.938
Low pressure	990	29.23	0.977
Standard pressure	1013.25	29.92	1.000
High pressure	1030	30.42	1.017
Very high pressure	1050	31.01	1.036

Medical Pressure: Blood Pressure Readings

Blood pressure is measured in mmHg and is expressed as two numbers: systolic (pressure during heart contraction) over diastolic (pressure between beats). Understanding these values is important for health monitoring:

Category	Systolic (mmHg)	Diastolic (mmHg)	Systolic (kPa)
Low	< 90	< 60	< 12.0
Normal	90–120	60–80	12.0–16.0
Elevated	120–129	< 80	16.0–17.2
High (Stage 1)	130–139	80–89	17.3–18.5
High (Stage 2)	140–179	90–119	18.7–23.9
Hypertensive crisis	≥ 180	≥ 120	≥ 24.0

Tips for Pressure Conversions

Know the standard reference: 1 atm = 101,325 Pa = 1.01325 bar = 14.696 PSI = 760 mmHg. Memorizing this one equivalence helps you derive most other conversions.
Do not confuse gauge and absolute pressure: Gauge pressure (PSIG) is relative to atmospheric pressure, while absolute pressure (PSIA) includes atmospheric pressure. 0 PSIG = 14.7 PSIA at sea level.
Check the unit system: European equipment may specify pressure in bar, while American equipment uses PSI. Always verify before applying values.
Be precise with medical values: Blood pressure readings should always be in mmHg. Converting to other units can introduce rounding errors that affect medical decisions.
Use an online converter: For complex or critical conversions, use our Universal Unit Converter to ensure accuracy.

Pro Tip: When working with tire pressure, remember the handy approximations: 1 bar ≈ 14.5 PSI and 1 PSI ≈ 7 kPa. For quick mental conversions, 2.2 bar ≈ 32 PSI (typical car tire pressure), which works for most everyday vehicle maintenance needs.

Pressure Unit Conversions: Complete Reference

Understanding Pressure and Its Units

Common Pressure Units

Key Conversion Factors

Common Pressure Conversions

PSI to kPa

kPa to PSI

Bar to PSI

PSI to Bar

Atmospheres to PSI

mmHg to kPa

Comprehensive Pressure Conversion Chart

Real-World Pressure Values

Meteorological Pressure Conversions

Medical Pressure: Blood Pressure Readings

Tips for Pressure Conversions

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