Pressure Converter
Convert between different pressure units - Pascal, Bar, PSI, Atmosphere, mmHg, and more.
Pressure Converter
1 Atmosphere =
14.695949
PSI (lb/in²)
All Conversions
Reference Values
- Standard atmosphere = 101,325 Pa
- 1 atm = 14.696 PSI = 1.01325 bar
- 1 bar = 100,000 Pa = 14.504 PSI
- 1 PSI = 6,894.76 Pa
- 760 mmHg = 1 atm (at 0°C)
What is Pressure Conversion?
Pressure conversion transforms force per unit area measurements between different systems. Pressure is fundamental in physics, engineering, meteorology, and medicine.
| Unit | Symbol | Definition | Pascals (Pa) |
|---|---|---|---|
| Pascal | Pa | SI unit (N/m²) | 1 |
| Kilopascal | kPa | 1,000 Pa | 1,000 |
| Bar | bar | 100,000 Pa | 100,000 |
| Atmosphere | atm | Standard sea level | 101,325 |
| PSI | psi | Pounds per sq inch | 6,894.76 |
| Torr/mmHg | Torr | 1/760 atm | 133.322 |
| Inches of Mercury | inHg | Weather reports | 3,386.39 |
Standard Atmosphere
Where:
- atm= Standard atmosphere
- Pa= Pascals
- psi= Pounds per square inch
- mmHg= Millimeters of mercury
SI Pressure Units: Pascal and Bar
The pascal (Pa) is the SI unit of pressure, defined as one newton per square meter. Because it's a small unit, kilopascals (kPa) and megapascals (MPa) are more commonly used.
| Unit | Pascals | Typical Use |
|---|---|---|
| Pascal (Pa) | 1 | Scientific calculations |
| Hectopascal (hPa) | 100 | Meteorology (= 1 mbar) |
| Kilopascal (kPa) | 1,000 | Tire pressure, hydraulics |
| Megapascal (MPa) | 1,000,000 | Material strength, hydraulics |
| Gigapascal (GPa) | 1,000,000,000 | Geology, material science |
| Bar | 100,000 | Industrial, tire pressure (Europe) |
| Millibar (mbar) | 100 | Weather forecasts |
Note: 1 bar is very close to 1 atm (1 atm = 1.01325 bar), making bar a convenient industrial unit.
Pascal Definition
Where:
- Pa= Pascal
- N= Newton (force)
- m²= Square meter (area)
Imperial Units: PSI and More
Pounds per square inch (PSI) is the primary pressure unit in the United States, used for tire pressure, air compressors, and hydraulic systems.
| Measurement | Typical PSI | kPa Equivalent | Bar Equivalent |
|---|---|---|---|
| Car tire pressure | 30-35 psi | 207-241 kPa | 2.07-2.41 bar |
| Bicycle tire (road) | 80-130 psi | 552-896 kPa | 5.5-9.0 bar |
| Bicycle tire (MTB) | 25-35 psi | 172-241 kPa | 1.7-2.4 bar |
| Home water pressure | 40-60 psi | 276-414 kPa | 2.8-4.1 bar |
| Fire hydrant | 50-150 psi | 345-1,034 kPa | 3.4-10.3 bar |
| Scuba tank | 3,000 psi | 20,684 kPa | 207 bar |
PSI Conversions
Where:
- psi= Pounds per square inch
- kPa= Kilopascals
- bar= Bar
Atmospheric and Weather Pressure
Atmospheric pressure is the force exerted by the weight of air above a point. It varies with altitude and weather conditions.
| Condition | Pressure (hPa) | inHg | Description |
|---|---|---|---|
| Standard atmosphere | 1013.25 | 29.92 | Sea level reference |
| High pressure system | >1020 | >30.12 | Fair weather expected |
| Low pressure system | <1000 | <29.53 | Unsettled weather |
| Hurricane center | 920-960 | 27.2-28.3 | Severe low pressure |
| Denver, CO (5,280 ft) | ~840 | ~24.8 | Mile-high city |
| Mount Everest summit | ~330 | ~9.7 | About 1/3 sea level |
Barometric formula: Pressure decreases by about 12 hPa per 100 meters of altitude gain near sea level.
Altitude Pressure Relationship
Where:
- P= Pressure at altitude
- P₀= Sea level pressure
- h= Altitude in meters
- H= Scale height (~8.5 km)
Medical Pressure Measurements
Medicine uses specialized pressure units, particularly mmHg (millimeters of mercury) for blood pressure and cmH₂O for respiratory pressures.
| Measurement | Normal Range | Unit | kPa Equivalent |
|---|---|---|---|
| Blood pressure (systolic) | 90-120 | mmHg | 12-16 kPa |
| Blood pressure (diastolic) | 60-80 | mmHg | 8-10.7 kPa |
| Intraocular pressure | 10-21 | mmHg | 1.3-2.8 kPa |
| Intracranial pressure | 5-15 | mmHg | 0.7-2.0 kPa |
| CPAP machine | 4-20 | cmH₂O | 0.4-2.0 kPa |
| Ventilator PEEP | 5-15 | cmH₂O | 0.5-1.5 kPa |
Blood pressure is measured in mmHg worldwide due to historical use of mercury sphygmomanometers. 120/80 mmHg remains the gold standard reading format.
mmHg Conversion
Where:
- mmHg= Millimeters of mercury
- Torr= Torricelli (same as mmHg)
- kPa= Kilopascals
Absolute vs. Gauge Pressure
Understanding the difference between absolute and gauge pressure is critical for many applications.
| Type | Reference | Symbol | Example Use |
|---|---|---|---|
| Absolute pressure | Perfect vacuum (0) | psia, kPa(a) | Scientific work, altitude |
| Gauge pressure | Atmospheric (0) | psig, kPa(g) | Tire pressure, tanks |
| Vacuum pressure | Below atmospheric | inHg vac | HVAC, industrial |
Key relationship: Absolute = Gauge + Atmospheric. A tire showing 32 psig is actually about 46.7 psia (32 + 14.7 atm).
Vacuum: Often expressed as inches of mercury (inHg) below atmospheric. Full vacuum at sea level is about 29.92 inHg.
Pressure Relationship
Where:
- P_absolute= Absolute pressure (psia)
- P_gauge= Gauge pressure (psig)
- P_atmospheric= Atmospheric (~14.7 psi)
Hydraulic and Industrial Pressure
Industrial and hydraulic systems often operate at high pressures, requiring robust measurement units:
| Application | Typical Pressure | MPa | PSI |
|---|---|---|---|
| Hydraulic brake system | Medium | 10-20 MPa | 1,450-2,900 psi |
| Hydraulic excavator | High | 25-35 MPa | 3,625-5,075 psi |
| Waterjet cutter | Very high | 400-600 MPa | 58,000-87,000 psi |
| Diesel fuel injection | Extreme | 200-300 MPa | 29,000-43,500 psi |
| Natural gas pipeline | Medium | 7-10 MPa | 1,000-1,450 psi |
| Propane tank | Low | 0.5-2 MPa | 70-290 psi |
Safety note: High-pressure systems can be extremely dangerous. Even small leaks can cause severe injuries due to fluid injection.
Worked Examples
Convert Tire Pressure
Problem:
A car tire requires 35 psi. What is this in kPa and bar for a European gauge?
Solution Steps:
- 11 psi = 6.895 kPa
- 235 psi × 6.895 = 241.3 kPa
- 31 bar = 100 kPa, so 241.3 ÷ 100 = 2.41 bar
- 4Or directly: 35 psi × 0.0689 bar/psi = 2.41 bar
Result:
35 psi = 241 kPa = 2.41 bar
Convert Weather Pressure
Problem:
The barometer reads 30.15 inHg. Convert to millibars (hPa) and kPa.
Solution Steps:
- 11 inHg = 33.864 hPa (millibars)
- 230.15 inHg × 33.864 = 1,021.0 hPa
- 31 hPa = 0.1 kPa, so 1,021.0 hPa = 102.1 kPa
- 4This is slightly above standard (1013.25 hPa), indicating high pressure
Result:
30.15 inHg = 1,021 hPa (mb) = 102.1 kPa
Convert Blood Pressure
Problem:
Blood pressure is 120/80 mmHg. Express in kPa.
Solution Steps:
- 11 mmHg = 0.133322 kPa
- 2Systolic: 120 mmHg × 0.133322 = 16.0 kPa
- 3Diastolic: 80 mmHg × 0.133322 = 10.7 kPa
- 4Blood pressure = 16.0/10.7 kPa
Result:
120/80 mmHg = 16.0/10.7 kPa
Tips & Best Practices
- ✓1 atm ≈ 1 bar ≈ 100 kPa ≈ 14.7 psi ≈ 760 mmHg - memorize these approximations
- ✓For tire pressure: psi × 0.07 ≈ bar, or psi × 7 ≈ kPa
- ✓Gauge pressure (psig) + 14.7 = absolute pressure (psia) at sea level
- ✓Weather: rising pressure (>1020 hPa) = fair; falling pressure (<1000 hPa) = unsettled
- ✓Blood pressure: 120/80 mmHg is often expressed as 16/10.7 kPa in metric countries
- ✓Altitude rule: pressure drops ~12 hPa per 100m elevation gain
- ✓1 Torr = 1 mmHg exactly (named after Evangelista Torricelli)
Frequently Asked Questions
Sources & References
Last updated: 2026-01-22