Pressure Converter
Convert between PSI, bar, pascal, atmosphere, and other pressure units
Common Pressure Conversions
Pressure in Real Life
Sea Level
≈ 1 atm (101.3 kPa, 14.7 psi)
Car Tire
≈ 32 psi (220 kPa, 2.2 bar)
Blood Pressure
≈ 120/80 mmHg (16/10.7 kPa)
Water Depth
10m depth ≈ +1 atm pressure
About Pressure Measurement
What is Pressure?
Pressure is defined as the force applied perpendicular to a surface per unit area. It is a fundamental physical quantity that describes how much force is distributed over a given area. The mathematical relationship is expressed as:
P = F/A
Where: P = Pressure, F = Force, A = Area
In the International System of Units (SI), pressure is measured in pascals (Pa), where 1 Pa equals 1 newton per square meter (N/m²). This fundamental relationship connects pressure to force and area, making it crucial in engineering, physics, and various scientific applications.
Common Pressure Units and Conversions
| Unit | Symbol | Definition | Conversion to Pa |
|---|---|---|---|
| Pascal | Pa | SI base unit | 1 Pa |
| Kilopascal | kPa | 1000 pascals | 1000 Pa |
| Bar | bar | 100,000 pascals | 100,000 Pa |
| Pounds per Square Inch | psi | Imperial unit | 6,894.76 Pa |
| Atmosphere | atm | Standard atmospheric pressure | 101,325 Pa |
| Torr | Torr | 1/760 of atmosphere | 133.322 Pa |
| Millimeters of Mercury | mmHg | Medical pressure unit | 133.322 Pa |
Types of Pressure
Absolute Pressure
Measured relative to a perfect vacuum (zero pressure). The formula is:
Pabs = Pgauge + Patm
Where Patm is atmospheric pressure (101.325 kPa at sea level)
Gauge Pressure
Measured relative to atmospheric pressure. Most pressure gauges read gauge pressure:
Pgauge = Pabs - Patm
When gauge pressure is negative, it indicates vacuum pressure
Pressure Measurement Instruments
Manometers
U-tube manometers use liquid columns (usually mercury or water) to measure pressure differences. The pressure is calculated using the formula: P = ρgh, where ρ is fluid density, g is gravitational acceleration, and h is the height difference.
Bourdon Tube Gauges
Mechanical pressure gauges that use a curved tube that straightens under pressure, converting pressure into mechanical displacement. Commonly used in industrial applications for measuring pressures from 0.6 to 7,000 bar.
Electronic Pressure Sensors
Modern sensors using piezoelectric, capacitive, or strain gauge technologies. These provide high accuracy and can measure pressures from millipascals to gigapascals with digital output for automated systems.
Barometers
Specialized instruments for measuring atmospheric pressure. Mercury barometers use the height of a mercury column, while aneroid barometers use a sealed chamber that expands and contracts with pressure changes.
Pressure in Fluid Dynamics
In fluid mechanics, pressure plays a crucial role in understanding fluid behavior. The fundamental relationship between pressure, density, and height in a static fluid is given by:
P = P0 + ρgh
Hydrostatic pressure formula: P0 = surface pressure, ρ = fluid density, g = gravity, h = depth
This equation explains why pressure increases with depth in oceans and why blood pressure varies with body position. For every 10 meters of water depth, pressure increases by approximately 1 atmosphere.
Real-World Pressure Examples
| Application | Typical Pressure | Units | Context |
|---|---|---|---|
| Atmospheric Pressure (Sea Level) | 101.3 | kPa | Standard reference pressure |
| Automotive Tire | 220 | kPa | Typical passenger car pressure |
| Blood Pressure (Systolic) | 16 | kPa | Normal adult systolic pressure |
| Scuba Diving (30m depth) | 400 | kPa | 4 atmospheres total pressure |
| Industrial Hydraulic System | 20,000 | kPa | Heavy machinery operation |
| Jet Engine Combustion | 2,000,000 | kPa | High-performance aircraft |
Why Pressure Measurement Matters
Safety and Reliability
- • Pressure vessel integrity monitoring
- • Pipeline leak detection systems
- • Aircraft cabin pressure regulation
- • Medical device safety standards
- • Industrial process control
Scientific Research
- • Weather forecasting and meteorology
- • Oceanography and deep-sea research
- • Material science and testing
- • Aerospace engineering
- • Biomedical research
Pressure Conversion Chart
Quick Reference: Common pressure unit conversions for everyday use
1 atm =
101.325 kPa
14.696 psi
1.013 bar
1 bar =
100 kPa
14.504 psi
0.987 atm
1 psi =
6.895 kPa
0.069 bar
0.068 atm
1 kPa =
0.145 psi
0.01 bar
0.0099 atm
Frequently Asked Questions
How does altitude affect pressure?
Atmospheric pressure decreases with altitude following an exponential decay. At 5,500 meters (18,000 feet), pressure is about half of sea level pressure. This affects aircraft performance, breathing, and weather patterns.
What is the difference between PSI and PSIG?
PSI (pounds per square inch) can refer to absolute pressure, while PSIG (pounds per square inch gauge) specifically refers to gauge pressure. PSIG is more common in industrial applications where atmospheric pressure is the reference point.
Why do we use different pressure units?
Different industries and regions have historical preferences. PSI is common in the US, bar in Europe, pascals in scientific work, and mmHg in medical applications. Each unit is convenient for its typical pressure range and application.
Frequently Asked Questions About Pressure Conversion
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