Pressure Conversion Formulas
Complete formulas for converting between different pressure units including PSI, Pascals, bar, mmHg, and specialized pressure measurements.
๐ก๏ธ Pressure Unit Overview
SI Units
Pascal (Pa): Base SI unit
kPa: 1,000 Pa
MPa: 1,000,000 Pa
Metric
Bar: 100,000 Pa
mbar: 0.001 bar
atm: Atmospheric pressure
Imperial
PSI: Pounds per square inch
PSIG: Gauge pressure
PSIA: Absolute pressure
Mercury/Water
mmHg: Millimeters mercury
inHg: Inches mercury
inH2O: Inches water column
๐ Basic Pressure Conversion Formulas
SI Unit Conversions
Pascal to kPa
Example: 25,000 Pa
25,000 Pa = 25 kPa
kPa to MPa
Example: 3,500 kPa
3,500 kPa = 3.5 MPa
Pascal to Bar
Example: 200,000 Pa
200,000 Pa = 2 bar
PSI Conversions
PSI to Pascal
Example: 50 PSI
50 PSI = 344.75 kPa
PSI to Bar
Example: 100 PSI
100 PSI = 6.89 bar
๐ง Mercury & Water Column Conversions
Mercury Column Conversions
mmHg to Pascal
Example: 760 mmHg
760 mmHg = 101.325 kPa = 1 atm
inHg to PSI
Example: 29.92 inHg
29.92 inHg = 14.7 PSI
mmHg to inHg
Example: 760 mmHg
760 mmHg = 29.92 inHg
Water Column Conversions
inH2O to Pascal
Example: 10 inH2O
10 inH2O = 2.49 kPa
inH2O to PSI
Example: 27.68 inH2O
27.68 inH2O = 1.0 PSI
๐ Atmospheric Pressure Standards
Standard Atmospheric Pressure
Sea Level Standard
1 atm = 101,325 Pa
1 atm = 101.325 kPa
1 atm = 1.01325 bar
1 atm = 14.696 PSIA
1 atm = 760 mmHg
1 atm = 29.92 inHg
Altitude Effects
Approximate formula:
h = altitude in meters
At 1000m: P = 89.88 kPa
11% pressure drop per 1000m
Gauge vs Absolute Pressure
Pressure Relationships
Example: 30 PSIG tire pressure
Gauge pressure: 30 PSIG
Absolute pressure: 44.7 PSIA
Always specify gauge or absolute
Vacuum Measurements
Example: 5 PSIA absolute
In inHg:
Vacuum level: 66% (9.7/14.7)
Strong vacuum condition
๐ Pressure Conversion Reference Table
| Application | Pascal (Pa) | PSI | Bar | mmHg |
|---|---|---|---|---|
| Atmospheric (Sea Level) | 101,325 | 14.7 | 1.013 | 760 |
| Car Tire | 241,317 | 35 | 2.41 | 1,810 |
| Water Pressure (10m depth) | 98,100 | 14.2 | 0.981 | 736 |
| HVAC Duct (1 inH2O) | 249 | 0.036 | 0.00249 | 1.87 |
| High Pressure (1000 PSI) | 6,895,000 | 1,000 | 68.95 | 51,715 |
๐ฌ Specialized Pressure Applications
Industrial Process Pressures
Steam System Pressures
Low pressure steam: 15 PSI (103 kPa)
Medium pressure: 125 PSI (862 kPa)
High pressure: 600 PSI (4.1 MPa)
Supercritical: 3,200+ PSI (22+ MPa)
Hydraulic Systems
Mobile hydraulics: 3,000 PSI (207 bar)
Industrial hydraulics: 5,000 PSI (345 bar)
Heavy equipment: 6,000 PSI (414 bar)
Waterjet cutting: 90,000 PSI (6,200 bar)
Laboratory & Scientific Pressures
Vacuum Levels
Rough vacuum: 1-0.1 mbar
High vacuum: 10โปยณ-10โปโท mbar
Ultra-high vacuum: <10โปโท mbar
Deep space: ~10โปยนโท mbar
Gas Pressure Conversions
1 Torr = 1 mmHg = 133.322 Pa
1 mTorr = 0.133 Pa
760 Torr = 1 atm
Torr commonly used in vacuum