Pressure reference
Technical unit workspace
- Quantities
- 2
- Systems
- SI / US
Common pressure units:
- Pascal (Pa): SI unit of pressure
- Bar: 100,000 Pa, close to 1 atm
- PSI: pounds per square inch
- Atmosphere (atm): standard pressure
- mmHg/Torr: medical applications
Key relationships:
- 1 bar = 100 kPa = 14.5038 PSI
- 1 atm = 101.325 kPa = 14.696 PSI
- 1 PSI = 6.895 kPa = 0.06895 bar
Origins of Pressure Units:
The pascal (Pa) was adopted as the SI unit in 1971, named after Blaise Pascal who studied hydrostatics in the 17th century. Traditional units like pounds per square inch (PSI) and inches of mercury (inHg) date back to early engineering and meteorology practices.
Historical Measurement:
Barometric pressure was first measured by Evangelista Torricelli in 1643 using mercury columns, establishing the torr and mmHg units. The bar unit was introduced around 1900 and standardized to exactly 100,000 pascals for meteorological use.
Standard Atmosphere:
The standard atmosphere (atm) was defined in the early 20th century as 101,325 pascals, representing the average atmospheric pressure at sea level, used to standardize engineering and scientific calculations.
Pascals are used for:
- Scientific calculations
- Acoustics and sound pressure
- Materials science
- Advanced engineering
PSI and Bar are used for:
- Tire pressure (PSI in US, Bar in Europe)
- Industrial hydraulics and pneumatics
- Plumbing and water systems
- Compressed gas cylinders
Other units:
- mmHg/Torr: Medical blood pressure
- inHg: Aviation altimeters
- Bar/Millibar: Meteorology
- kPa: HVAC, refrigeration systems
Pressure Conversion Calculator
Quick answer
Formula: kPa = psi x 6.89476
Converting Pound per Square Inch to Kilopascal with 6-place display precision.
Measurement type
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Quick pairs
Jump to the most common unit combinations
Quantity
Pressure
Input unit
Pound per Square Inch (psi)
Output unit
Kilopascal (kPa)
Popular pressure pair converters
Published PSI ↔ kPa calculators, plus the related force pair used in pressure work.
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What are Pressure Measurements?
Pressure is the force applied perpendicular to a surface per unit area. It's a fundamental physical quantity that measures how force is distributed over an area. The SI unit of pressure is the pascal (Pa), defined as one newton per square meter (N/m²).
Different pressure units evolved to suit various industries and applications. While pascals are standard in scientific contexts, pounds per square inch (PSI) remain common in the US and UK for many applications, bar units are prevalent in Europe, and mmHg (millimeters of mercury) are used in medical settings.
Learn more from NIST or Bureau International des Poids et Mesures (BIPM).
Common Pressure Conversions
| From | To | Multiply By | Example |
|---|---|---|---|
| Pascal (Pa) | Bar | 0.00001 | 100,000 Pa = 1 bar |
| Bar | PSI | 14.5038 | 1 bar = 14.5038 PSI |
| PSI | kPa | 6.89476 | 1 PSI = 6.89476 kPa |
| Atmosphere (atm) | kPa | 101.325 | 1 atm = 101.325 kPa |
| mmHg (Torr) | kPa | 0.133322 | 760 mmHg = 101.325 kPa |
| inHg | hPa | 33.8639 | 1 inHg = 33.8639 hPa |
| kPa | inH₂O | 4.01463 | 1 kPa = 4.01463 inH₂O |
Pressure Gradient Conversions
| From | To | Multiply By | Example |
|---|---|---|---|
| PSI/ft | kPa/m | 22.6219 | 1 PSI/ft = 22.6219 kPa/m |
| bar/km | PSI/mile | 23.3603 | 1 bar/km = 23.3603 PSI/mile |
| Pa/m | PSI/ft | 0.0000442 | 10,000 Pa/m = 0.442 PSI/ft |
| mmH₂O/m | Pa/m | 9.80665 | 1 mmH₂O/m = 9.80665 Pa/m |
Practical Applications of Pressure Conversions
Automotive Industry
- Converting tire pressure between PSI, bar, and kPa for international vehicles
- Calculating hydraulic brake system pressures
- Setting fuel injector and turbocharger pressures
- Testing engine compression ratios
Medical & Healthcare
- Converting blood pressure readings between mmHg and kPa
- Setting and monitoring ventilator pressures
- Calibrating medical vacuum systems
- Measuring intraocular pressure in ophthalmology
Industrial & Engineering
- Designing hydraulic and pneumatic systems with various pressure ratings
- Calculating pressure drops in pipelines and fluid distribution systems
- Setting safety relief valve thresholds in process plants
- Converting between ASME and other international pressure vessel codes
Environmental & Meteorology
- Converting barometric pressure between inHg, mbar, and hPa for weather forecasting
- Altitude corrections for pressure readings
- Analyzing climate data across different measurement standards
- Calibrating environmental monitoring equipment
Consumer Applications
- Setting home water pressure regulators
- Adjusting air compressors for various tools and applications
- Filling bicycle and sports equipment tires to correct pressures
- Setting up aquarium and hydroponics systems
Educational Resource
This educational video from The Organic Chemistry Tutor explains how to convert between different pressure units including atmospheres, millimeters of mercury, torr, kilopascals, and PSI. With over 1 million views, it's a highly-regarded resource for understanding pressure measurement concepts and conversion techniques essential for chemistry, physics, and engineering applications.
Pressure Conversion Resources
Get our comprehensive pressure conversion chart showing relationships between pascals, PSI, bar, atmospheres, and other pressure units for quick reference in engineering calculations and everyday applications.
Pressure Conversion FAQs
Find answers to common questions about pressure measurements and conversions.
What are the main units used for measuring pressure?
The main pressure measurement units are: 1) Pascal (Pa) - SI unit, force per area, 2) PSI (pounds per square inch) - common in US/UK, 3) Bar - metric unit, 1 bar = 100 kPa, 4) Atmosphere (atm) - reference to average air pressure, 5) Torr/mmHg - medical/vacuum measurements, 6) Kilopascal (kPa) - industrial applications, 7) Megapascal (MPa) - high-pressure systems.
How do you convert between common pressure units?
Common pressure conversions include: 1) 1 bar = 14.5038 PSI = 100 kPa, 2) 1 atmosphere = 1.01325 bar = 14.696 PSI, 3) 1 PSI = 6.895 kPa = 51.715 mmHg, 4) 1 kPa = 0.145038 PSI = 7.50062 mmHg, 5) 1 MPa = 145.038 PSI = 10 bar. Always verify critical conversions with calibrated instruments.
What are typical pressure values in different applications?
Common pressure values include: 1) Car tire pressure: 30-35 PSI (2.1-2.4 bar), 2) Atmospheric pressure: 14.7 PSI (1013.25 hPa), 3) Bicycle tire: 40-120 PSI (2.8-8.3 bar), 4) Blood pressure: 120/80 mmHg, 5) Industrial hydraulics: 1000-5000 PSI (69-345 bar), 6) Natural gas lines: 60 PSI (4.14 bar).
How do you measure pressure accurately?
Accurate pressure measurement requires: 1) Calibrated pressure gauges/sensors, 2) Proper installation and orientation, 3) Temperature compensation, 4) Regular calibration checks, 5) Appropriate range selection, 6) Consideration of static vs. dynamic pressure, 7) Environmental condition monitoring.
What is the relationship between pressure and other physical quantities?
Pressure relationships include: 1) Pressure = Force ÷ Area (P = F/A), 2) Hydrostatic pressure = density × gravity × height (P = ρgh), 3) Ideal gas law: PV = nRT, 4) Gauge vs. absolute pressure difference = atmospheric pressure, 5) Pressure affects boiling point and phase changes.
How do you choose the right pressure unit for your application?
Select pressure units based on: 1) Industry standards (HVAC uses PSI, weather uses hPa), 2) Equipment specifications, 3) Local regulations and codes, 4) Measurement range and precision needed, 5) End-user familiarity, 6) International vs. local use, 7) Safety requirements.
What factors affect pressure measurements?
Pressure measurements are affected by: 1) Temperature changes, 2) Altitude and atmospheric conditions, 3) System dynamics and flow effects, 4) Sensor calibration and accuracy, 5) Installation position and orientation, 6) Vibration and pulsation, 7) Media properties (gas/liquid).
How do you handle pressure conversions in critical applications?
For critical pressure conversions: 1) Use certified conversion factors, 2) Double-check calculations independently, 3) Consider safety margins and tolerances, 4) Document all conversions and assumptions, 5) Use appropriate significant figures, 6) Verify with physical measurements when possible, 7) Consider system-specific requirements.
Pressure conversion shortcuts
Engineering pressure calculators connected to adjacent force and power topics.