Pressure Conversion Calculator
Convert between all pressure units: PSI, Bar, Pascal, Atmosphere, and more
Universal Pressure Converter
All Pressure Units
Pressure measures force distributed over an area, expressing how much force acts per unit of surface. Different measurement systems and applications have created numerous pressure units, each serving specific scientific, engineering, or practical purposes across industries from meteorology to automotive engineering.
SI (Metric) Pressure Units
- Pascal (Pa): SI base unit, 1 Newton per square meter
- Kilopascal (kPa): 1,000 Pa, common for engineering
- Megapascal (MPa): 1,000,000 Pa, high-pressure applications
- Bar: 100,000 Pa, meteorology and engineering
- Millibar (mbar): 100 Pa, weather reporting
Imperial/US Pressure Units
- PSI (lb/in²): Pounds per square inch, US standard
- PSF (lb/ft²): Pounds per square foot, construction
- inHg: Inches of mercury, weather/aviation
Atmospheric & Scientific Units
- Atmosphere (atm): Standard atmospheric pressure at sea level
- Torr: 1/760 of atmosphere, vacuum measurements
- mmHg: Millimeters of mercury, medical/scientific
Pressure Conversion Chart
What is Pressure Conversion?
Pressure conversion translates measurements of force per unit area from one unit system to another, enabling engineers, scientists, and technicians to work across international standards, interpret specifications from different sources, and operate equipment calibrated in various measurement systems. Pressure represents one of the fundamental physical quantities in thermodynamics, fluid mechanics, and material science, making accurate conversion essential for applications ranging from tire inflation to industrial process control.
The necessity for pressure conversion arises from diverse measurement traditions across industries and countries. Meteorologists use millibars or inches of mercury for atmospheric pressure, automotive engineers specify tire pressure in PSI or bar, scientists use Pascals as the SI standard, and medical professionals measure blood pressure in millimeters of mercury. Each unit provides practical, readable values for its specific application context, requiring conversion skills to bridge these different measurement conventions.
Understanding pressure conversion extends beyond simple arithmetic to recognizing relationships between force, area, and the physical phenomena being measured. Pressure equals force divided by area, making it an intensive property independent of system size. Converting accurately between pressure units ensures safety in pressurized systems, enables international collaboration in engineering projects, maintains equipment specifications across diverse standards, and prevents costly errors in applications where pressure control proves critical to process success, product quality, and system safety.
Pressure Conversion Formulae
Fundamental Pressure Equation
Basic Pressure Definition:
\[ P = \frac{F}{A} \]
Where P = pressure, F = force, A = area
Key Conversion Formulas
PSI to kPa:
\[ \text{kPa} = \text{PSI} \times 6.89476 \]
Bar to PSI:
\[ \text{PSI} = \text{Bar} \times 14.5038 \]
atm to Pa:
\[ \text{Pa} = \text{atm} \times 101{,}325 \]
mmHg to kPa:
\[ \text{kPa} = \text{mmHg} \times 0.133322 \]
Uses of Pressure Conversion
Automotive Applications
Tire pressure specifications vary globally—US uses PSI (typically 32-35 PSI), Europe uses bar (2.2-2.4 bar). Converting ensures proper inflation maintaining fuel efficiency, tire wear, and vehicle safety. Engine boost pressure, brake systems, and hydraulic systems all require accurate pressure conversion across international vehicle specifications and diagnostic equipment.
Weather and Aviation
Meteorology uses millibars or hectopascals for atmospheric pressure (standard: 1013 mbar). Aviation uses inches of mercury for altimeter settings. Converting between units enables pilots to set instruments correctly, meteorologists to share data internationally, and weather forecasters to communicate pressure systems accurately across different measurement traditions.
Medical Applications
Blood pressure measures in mmHg (normal: 120/80 mmHg). Medical equipment specifications may use different units. Converting ensures accurate diagnosis, proper equipment calibration, and consistent medical communication. Respiratory therapy, anesthesia, and hyperbaric medicine all require precise pressure conversion for patient safety and treatment effectiveness.
Industrial Process Control
Manufacturing processes specify pressure in various units depending on equipment origin and industry standards. Chemical reactors, hydraulic systems, pneumatic controls, and steam systems require accurate pressure conversion to maintain process parameters, ensure safety, prevent equipment damage, and maintain product quality across international operations with mixed measurement systems.
HVAC and Refrigeration
Heating, ventilation, air conditioning, and refrigeration systems specify pressure in PSI, kPa, or bar depending on country and manufacturer. Converting enables proper system charging, leak testing, and performance verification. Refrigerant pressures, duct static pressure, and system diagnostics all require accurate conversion across diverse equipment and specifications.
Scientific Research
Scientific publications use SI units (Pascals), but equipment from different countries may display other units. Converting enables reproducible research, accurate data comparison across studies, and proper equipment operation. Vacuum systems (Torr), high-pressure research (GPa), and atmospheric studies all require fluency in multiple pressure unit systems.
How to Convert Pressure Units
Complete Conversion Guide
Using the Calculator
- Enter your pressure value in the input field
- Select your starting unit from "From Unit" dropdown
- Select your target unit from "To Unit" dropdown
- Click "Convert Pressure" for instant results
- Results display with appropriate precision
Common Conversion Examples
Example 1: Convert 30 PSI to kPa (tire pressure)
\[ 30 \text{ PSI} \times 6.89476 = 206.84 \text{ kPa} \]
Example 2: Convert 2.5 bar to PSI
\[ 2.5 \text{ bar} \times 14.5038 = 36.26 \text{ PSI} \]
Example 3: Convert 120 mmHg to kPa (blood pressure)
\[ 120 \text{ mmHg} \times 0.133322 = 16.0 \text{ kPa} \]
Quick Conversion Tips
- PSI to bar: divide by ~14.5 (30 PSI ≈ 2 bar)
- Bar to PSI: multiply by ~14.5 (2 bar ≈ 29 PSI)
- kPa to PSI: divide by ~6.9 (200 kPa ≈ 29 PSI)
- atm to PSI: multiply by ~14.7 (1 atm ≈ 14.7 PSI)
Frequently Asked Questions
1. What is the difference between PSI and bar?
PSI (pounds per square inch) is the imperial pressure unit, while bar is a metric unit. 1 bar = 14.5038 PSI, or approximately 14.5 PSI. Bar is commonly used in Europe for tire pressure (2.0-2.5 bar typical), while PSI is standard in the United States (30-35 PSI typical). Both measure the same physical property—pressure—just in different unit systems.
2. How do I convert PSI to kPa?
Multiply PSI by 6.89476 to get kPa. Example: 30 PSI × 6.89476 = 206.84 kPa. For quick mental math, multiply PSI by 7 for a close approximation (30 PSI × 7 = 210 kPa, within 2% of exact value). This conversion frequently appears when working with international tire pressure specifications or technical equipment.
3. What is standard atmospheric pressure?
Standard atmospheric pressure at sea level equals: 101,325 Pa (101.325 kPa), 1.01325 bar, 1 atmosphere (atm), 14.696 PSI, 760 mmHg (or Torr), or 29.92 inHg. This standard reference pressure varies with altitude and weather. Higher elevations have lower atmospheric pressure—at 5,000 feet elevation, atmospheric pressure drops to about 12.2 PSI.
4. Why do tire pressure gauges show different units?
Manufacturers produce gauges for different regional markets. US gauges display PSI, European gauges show bar, and some display multiple units. Vehicle specifications match regional standards—American cars specify PSI, European cars specify bar. Modern digital gauges often allow unit switching. Always verify your gauge displays the same units as your vehicle's specification to prevent under or over-inflation.
5. What does "gauge pressure" vs "absolute pressure" mean?
Gauge pressure measures pressure relative to atmospheric pressure (PSIG = gauge). Absolute pressure measures pressure relative to perfect vacuum (PSIA = absolute). Tire pressure gauges show gauge pressure—30 PSI gauge actually means 30 + 14.7 = 44.7 PSI absolute. Most everyday pressure measurements use gauge pressure. Scientific and engineering calculations often require absolute pressure.
6. How accurate do pressure conversions need to be?
Accuracy depends on application. Tire pressure: ±1 PSI acceptable. Industrial processes: ±0.5% typical. Scientific research: ±0.1% or better. Medical applications: match device specifications. Most conversion calculators provide more precision than measurement instruments can achieve. Round converted values to match your pressure gauge resolution—excessive decimal places imply false precision beyond measurement capability.
7. Why is blood pressure measured in mmHg?
Historical reasons—early blood pressure devices used mercury columns. Height of mercury column directly indicated pressure. Despite modern electronic devices, medical profession retained mmHg for consistency with historical data and universal recognition. Normal blood pressure: 120/80 mmHg (16/10.7 kPa). The unit provides intuitive, memorable numbers in the typical human blood pressure range.
8. Can I convert pressure to force or area?
Not directly—pressure, force, and area are related but different quantities. To find force: Force = Pressure × Area. To find area: Area = Force ÷ Pressure. To find pressure: Pressure = Force ÷ Area. Example: 30 PSI over 10 square inches creates 300 pounds force. You need two of the three values to calculate the third.
9. What is the difference between Torr and mmHg?
For practical purposes, they're identical: 1 Torr = 1 mmHg = 133.322 Pa. Technically, Torr is defined as 1/760 of standard atmosphere, while mmHg depends on mercury density and gravity. The difference is negligible (0.000015%). Vacuum applications use Torr, medical applications use mmHg. Both measure the same pressure—choose the unit appropriate for your field.
10. Does temperature affect pressure conversion?
Pressure conversion factors remain constant—1 PSI always equals 6.89476 kPa regardless of temperature. However, temperature affects the actual pressure in a closed system (gas laws). Converting 30 PSI to kPa always gives 206.84 kPa, but the pressure in a tire increases with temperature. Conversion factors don't change; actual pressures do with temperature, volume, and gas quantity changes.