Pressure Units Converter
Reference data and engineering information about pressure units converter for basics applications.
Overview
Pressure is a fundamental quantity in engineering, defined as force per unit area. Various units are used across different systems, such as Pascal (Pa) in SI, bar in metric, pound per square inch (psi) in imperial, and others. This reference provides conversion factors, a practical example, and tools for converting between common pressure units.
Key Formulas
The basic formula for pressure is:
where is pressure, is force, and is area.
For unit conversion, multiplication factors are used. For instance, to convert from psi to Pa, multiply the value in psi by 6894.76.
Variables
| Symbol | Description | Unit |
|---|---|---|
| Pressure | Pa, bar, atm, psi, etc. | |
| Force | N | |
| Area | m² | |
| Pa | Pascal | 1 N/m² |
| bar | Bar | 10⁵ Pa |
| atm | Standard atmosphere | 101325 Pa |
| psi | Pound per square inch | 6894.76 Pa |
| mm Hg | Millimeter of mercury | 133.322 Pa |
| in Hg | Inch of mercury | 3386.39 Pa |
Pressure Conversion Tables
The SI unit of pressure is Pa or N/m2. Other pressure units, including bar, atmosphere, mm Hg, mm H2O, m H2O, kg/cm2, pound per square foot, pound per square inch, inches Hg and inches H2O, are listed below.
Note that kg/cm2 is technically incorrect as a pressure unit because kg is a mass unit, not a force unit. The corresponding force-based unit is kilogram-force per square centimetre, using standard gravity.
Unit | Pa (N/m²) | bar | atmosphere | mm Hg | mm H₂O | m H₂O | kg/cm² |
|---|---|---|---|---|---|---|---|
| Pa (N/m²) | 1 | 10⁻⁵ | 9.87×10⁻⁶ | 0.0075 | 0.1 | 10⁻⁴ | 1.02×10⁻⁵ |
| bar | 10⁵ | 1 | 0.987 | 750 | 1.0197×10⁴ | 10.197 | 1.0197 |
| atmosphere | 1.01×10⁵ | 1.013 | 1 | 759.9 | 10332 | 10.332 | 1.03 |
| mm Hg | 133.3 | 1.33×10⁻³ | 1.32×10⁻³ | 1 | 13.3 | 0.013 | 1.36×10⁻³ |
| mm H₂O | 10 | 0.000097 | 9.87×10⁻⁵ | 0.075 | 1 | 0.001 | 1.02×10⁻⁴ |
| m H₂O | 10⁴ | 0.097 | 9.87×10⁻² | 75 | 1000 | 1 | 0.102 |
| kg/cm² | 9.8×10⁴ | 0.98 | 0.97 | 735 | 10000 | 10 | 1 |
Source: engineeringtoolbox.com
Unit | pound/sq foot | pound/sq inch (psi) | inches Hg | inches H₂O |
|---|---|---|---|---|
| Pa (N/m²) | 0.021 | 1.450326×10⁻⁴ | 2.96×10⁻⁴ | 4.02×10⁻³ |
| bar | 2090 | 14.50 | 29.61 | 402 |
| atmosphere | 2117.5 | 14.69 | 29.92 | 407 |
| mm Hg | 2.79 | 0.019 | 0.039 | 0.54 |
| mm H₂O | 0.209 | 1.45×10⁻³ | 2.96×10⁻³ | 0.04 |
| m H₂O | 209 | 1.45 | 2.96 | 40.2 |
| kg/cm² | 2049 | 14.21 | 29.03 | 394 |
| pound/sq foot (psf) | 1 | 0.0069 | 0.014 | 0.19 |
| pound/sq inch (psi) | 144 | 1 | 2.04 | 27.7 |
| inches Hg | 70.8 | 0.49 | 1 | 13.57 |
| inches H₂O | 5.2 | 0.036 | 0.074 | 1 |
Source: engineeringtoolbox.com
Some other Pressure Units
Some other pressure units used in engineering and technical work include torr, technical atmosphere, standard atmosphere, pound per square foot, pound per square inch, inches mercury and inches water. The converter and tables on this page preserve these units as force per area equivalents.
psi to bar Nomogram
The original psi_bar.png nomogram is represented below as an interactive linear conversion using 1 psi = 0.0689476 bar.
psi to bar Nomogram
psi to kPa Nomogram
The original psi_kpa.png nomogram is represented below as an interactive linear conversion using 1 psi = 6.89476 kPa.
psi to kPa Nomogram
kPa vs bar, psi, mmH2O and inH2O
The original kPa_vs_bar_psi_mmh2o_inh2o.png comparison chart is represented below as interactive data.
kPa vs bar, psi, mmH2O and inH2O
Example Calculation
Convert 10 psi to Pa using the factor 6894.76:
.
Pressure Unit Converter
Restored Original Source Tables
The following tables are restored from the original source page to preserve the complete reference data.
Pressure Converter
Pa (N/m2) | bar | atmosphere | mm Hg | mm H2O | m H2O | kg/cm2 | Multiply by |
|---|---|---|---|---|---|---|---|
| Pa (N/m2) | 1 | 10-5 | 9.87×10-6 | 0.0075 | 0.1 | 10-4 | 1.02×10-5 |
| bar | 105 | 1 | 0.987 | 750 | 1.0197×104 | 10.197 | 1.0197 |
| atmosphere | 1.01×105 | 1.013 | 1 | 759.9 | 10332 | 10.332 | 1.03 |
| mm Hg | 133.3 | 1.33×10-3 | 1.32×10-3 | 1 | 13.3 | 0.013 | 1.36×10-3 |
| mm H2O | 10 | 0.000097 | 9.87×10-5 | 0.075 | 1 | 0.001 | 1.02×10-4 |
| m H2O | 104 | 0.097 | 9.87×10-2 | 75 | 1000 | 1 | 0.102 |
| kg/cm2 | 9.8×104 | 0.98 | 0.97 | 735 | 10000 | 10 | 1 |
| pound square feet | 47.8 | 4.78×10-4 | 4.72×10-4 | 0.36 | 4.78 | 4.78×10-3 | 4.88×10-4 |
| pound square inches (psi) | 6894.76 | 0.069 | 0.068 | 51.7 | 689.7 | 0.69 | 0.07 |
| inches Hg | 3377 | 0.0338 | 0.033 | 25.4 | 337.7 | 0.337 | 0.034 |
| inches H2O | 248.8 | 2.49×10-3 | 2.46×10-3 | 1.87 | 25.4 | 0.0254 | 0.0025 |
Source: engineeringtoolbox.com
Pressure Converter
pound square feet | pound square inches (psi) | inches Hg | inches H2O | Multiply by |
|---|---|---|---|---|
| Pa (N/m2) | 0.021 | 1.450326×10-4 | 2.96×10-4 | 4.02×10-3 |
| bar | 2090 | 14.5 | 29.61 | 402 |
| atmosphere | 2117.5 | 14.69 | 29.92 | 407 |
| mm Hg | 2.79 | 0.019 | 0.039 | 0.54 |
| mm H2O | 0.209 | 1.45×10-3 | 2.96×10-3 | 0.04 |
| m H2O | 209 | 1.45 | 2.96 | 40.2 |
| kg/cm2 | 2049 | 14.21 | 29.03 | 394 |
| pound square feet (psf) | 1 | 0.0069 | 0.014 | 0.19 |
| pound square inches (psi) | 144 | 1 | 2.04 | 27.7 |
| inches Hg | 70.8 | 0.49 | 1 | 13.57 |
| inches H2O | 5.2 | 0.036 | 0.074 | 1 |
Source: engineeringtoolbox.com
Original Source Images
The following original source images are preserved to avoid losing visual reference material. When an image contains chart or tabular data, its extracted values are represented in the page tables, calculators, or interactive charts; remaining images are retained as visual source references.
Engineering Notes
- Pressure is force per unit area; units like kg/cm² are technically incorrect because kilogram is a mass unit. For accurate use, multiply by gravitational acceleration (g ≈ 9.80665 m/s²) to convert to force-based units like N/m².
- Conversion factors assume standard conditions (e.g., 1 atm = 101325 Pa). For units like mm Hg and inches Hg, which depend on mercury density and gravity, variations with temperature and location can introduce errors in high-precision work.
- When performing engineering calculations, ensure all pressure values are converted to consistent units to avoid mistakes. For example, in fluid dynamics, mixing psi and Pa without conversion can lead to significant errors.
- The tables provide multiplication factors for direct conversion; for complex systems, consider using dimensional analysis or dedicated unit conversion software for reliability.