Pressure Unit Conversion
An all-in-one tool to convert between a wide range of pressure units, including PSI, bar, Pascals, and atmospheres.
Bookmark this Calculator!
Guide to Pressure Unit Conversion
Pressure is defined as force per unit area. It is a fundamental quantity in physics, engineering, meteorology, and many other sciences. Because it is used in so many different fields, numerous units have been developed over time. This can make converting between them confusing. This article provides an overview of common pressure units and how to convert between them.
The Base Unit: The Pascal (Pa)
The standard international (SI) unit for pressure is the Pascal (Pa), which is defined as one Newton of force per square meter (N/m²). Most pressure conversions use the Pascal as a base unit. For instance, to convert from PSI to bar, you would first convert PSI to Pascals, and then Pascals to bar.
Our calculator simplifies this by storing the conversion factor of each unit relative to the Pascal, allowing for direct and accurate conversions.
Common Pressure Units
- Pascal (Pa): The SI unit. It's a very small unit, so kilopascals (kPa) and megapascals (MPa) are often used.
- Pounds per square inch (psi): Common in the US, used for everything from tire pressure to industrial processes.
- Bar: Roughly equal to atmospheric pressure at sea level, making it a convenient unit. 1 bar = 100,000 Pa.
- Standard atmosphere (atm): Defined as the average atmospheric pressure at mean sea level. 1 atm = 101,325 Pa.
- Torr (mmHg): Originally defined as 1 millimeter of mercury. It's nearly identical to mmHg and is used in vacuum measurements.
- Inches of Water Gauge (inAq or inH₂O): Used for measuring small pressure differentials, for example in HVAC systems.
Conversion Example: PSI to Bar
Let's convert 14.5 psi to bar.
- First, convert psi to Pascals:
1 psi ≈ 6,894.76 Pa. So,14.5 psi * 6894.76 Pa/psi ≈ 100,000 Pa. - Next, convert Pascals to bar:
1 bar = 100,000 Pa. So,100,000 Pa / 100,000 Pa/bar = 1 bar.
Therefore, 14.5 psi is approximately equal to 1 bar.
Approximate Conversion Factors
| Unit | Equivalent to 1 atm |
|---|---|
| Pascals (Pa) | 101,325 |
| Kilopascals (kPa) | 101.325 |
| Pounds per square inch (psi) | ~14.696 |
| Bar | ~1.013 |
| Torr (mmHg) | 760 |
Frequently Asked Questions (FAQ)
- What is the difference between absolute and gauge pressure (e.g., psi vs. psig)?
- Absolute pressure (psia) is measured relative to a perfect vacuum. Gauge pressure (psig) is measured relative to the ambient atmospheric pressure. So,
Absolute Pressure = Gauge Pressure + Atmospheric Pressure. - Why are there so many units for pressure?
- Different industries and scientific fields developed units that were convenient for their specific applications. For example, meteorologists use millibars, while US engineers often use psi. This historical development led to the wide variety of units in use today.
- Which unit should I use?
- In scientific and most international contexts, the SI unit (Pascal) and its multiples (kPa, MPa) are standard. However, for everyday use in the US, psi is most common. For weather, you might see millibars or inches of mercury. The best unit depends on your context.
Similar Calculators
Convert land area from acres to hectares, two common units for measuring large plots of land.
A comprehensive tool to convert angles between various units, including degrees, radians, gradians, and revolutions.
Convert between angstroms and nanometers, two units of length used for very small scales in science and technology.
Convert between common units of area such as square feet, square meters, and acres.
Explore Other Calculators
Calculate your car's 0-60 mph time based on its horsepower and weight.
Quickly calculate the date that is 100 days from a starting date. Perfect for tracking 100-day challenges or project milestones.
Estimate your self-employment taxes as a freelancer or independent contractor. Helps you plan for quarterly tax payments and avoid surprises.
Find the date that is 120 days from any given start date. Useful for planning timelines, loan terms, and long-term projects.
Calculate the date that is 180 days (about six months) from a specific start date. Ideal for setting semi-annual goals or deadlines.
A simple tool to find the date that is exactly 30 days from a given start date. Commonly used for trial periods and monthly planning.
Quickly add or subtract 30 minutes from any given time. A handy tool for scheduling meetings, breaks, or appointments.
Project the growth of your 401(k) retirement savings over time. See how contributions, employer match, and investment returns can impact your nest egg.