Convert Pressure from bar to pounds per square inch (bar to psi)

Bar to Pound per Square Inch Conversion Formula

To convert a pressure from bar to pounds per square inch (psi), multiply by 14.5038.

• psi = bar × 14.5038

One bar is exactly 100,000 Pa and one psi is 6,894.76 Pa; dividing the first by the second gives 14.5038. Since one standard atmosphere is 1.01325 bar = 14.696 psi, a bar and an atmosphere differ by just 1.3% — so "1 bar ≈ 14.5 psi ≈ 1 atm" is a serviceable mental anchor across the everyday range.

Step-by-Step Example

A European tire placard specifies 2.5 bar and the only gauge at hand reads psi:

1. Take the pressure: 2.5 bar
2. Multiply by 14.5038: 2.5 × 14.5038 = 36.3 psi

Inflate to 36 psi and the placard is satisfied.

Quick Reference Table

Why Both Units Refuse to Die

The bar survives because it is almost an atmosphere in a clean decimal package (10⁵ Pa exactly), and the psi survives because an enormous installed base of American gauges, fittings and specifications is written in it — so the conversion between them is the daily bread of anyone servicing equipment across markets. Espresso machines are a small but vivid example: brew pressure is quoted at 9 bar in European literature and 130 psi in American manuals, the same number twice. Hydraulics scale the stakes up — a 350 bar system is 5,076 psi, and hose or fitting ratings mixed up between the two unit systems fail in ways that are genuinely dangerous.

The gauge-versus-absolute distinction travels with the number here as everywhere in pressure work: tire, compressor and hydraulic figures in both units are gauge readings, and converting the unit does not convert the reference frame. 2.5 bar gauge is 36.3 psig; it is also about 51 psia, and which of the two a formula needs depends on whether the atmosphere participates in the physics.

How many bar are in one pound per square inch? One pound per square inch (psi) contains 0.068947600004501395751 bar (bar) — the inverse of the factor above. Multiplying by 14.503768078 takes you from bar to pounds per square inch; multiplying by 0.068947600004501395751 brings you back.

Put in words: one bar equals 14.503768078 pounds per square inch, so the bar is the larger unit of this pair. Converting between them never changes the amount of pressure being measured — only the size of the unit you count it in.

What is a bar (bar)?

The bar is a metric unit of pressure.

It is defined as exactly 100 kilopascals (kPa), or 100,000 Pascals (Pa).

Although it is not an official part of the International System of Units (SI), it is widely accepted for use with the SI. The bar is a popular unit for measuring pressure because it is very close to the average atmospheric pressure on Earth at sea level.

Origin of the Bar

The term "bar" comes from the Greek word βάρος (baros), which means "weight."

The unit was introduced by British meteorologist William Napier Shaw in 1909. It is still widely used in meteorology, oceanography, and engineering.

Bar vs. Standard Atmosphere (atm)

A common point of confusion is the difference between a bar and a standard atmosphere (atm).

While they are very close in value, they are not the same:

• 1 bar = 100,000 Pascals (Pa)
• 1 atmosphere (atm) = 101,325 Pascals (Pa)

This means 1 bar is approximately equal to 0.987 atm. Because it's so close to atmospheric pressure and is a round number (100 kPa), the bar is a very convenient unit for many applications.

Common Applications of the Bar

The bar is a versatile unit used to measure pressure in many industrial and everyday contexts.

Common examples include:

• Automotive: Measuring tire pressure (often listed on a car's door jamb alongside PSI).
• Scuba Diving: Expressing the amount of air pressure inside diving tanks.
• Weather: Used by meteorologists for weather forecasting and reading atmospheric pressure.
• Plumbing & Pumps: Measuring water pressure in pipes and pump systems.
• Industrial: Measuring air pressure in pneumatic equipment and gas pressure in cylinders for welding.

What is a pound per square inch (psi)?

A pound per square inch (PSI) is a unit of pressure commonly used in the imperial system (which is standard in the United States).

It measures the amount of force applied over a single square inch of area.

Common Examples of PSI (Where is PSI Used?)

PSI is a critical measurement for safety and performance in many common items, including:

• Vehicle Tires: Proper tire pressure (PSI) ensures optimal handling, fuel efficiency, and tire life. You can find the recommended level on a sticker inside the driver's door.

• Home Water Pressure: Affects everything from shower performance to how well appliances like dishwashers and washing machines function.

• Sports Equipment: Items like footballs, basketballs, and soccer balls require a specific PSI to perform correctly and safely.

• Tools: Air compressors, pressure washers, and paint sprayers all have specific PSI ratings for safe and effective operation.

Converting PSI to Metric Units like Pascals and Bar

While PSI is standard in the imperial system, scientific and international contexts use metric (SI) units like the Pascal (Pa) and the bar.

• PSI to Pascal (Pa): The official SI unit for pressure.
  1 PSI ≈ 6,894.76 Pascals (or 6.895 kilopascals, kPa).

• PSI to Bar: A common unit in automotive and weather contexts. 1 bar is roughly equal to atmospheric pressure at sea level.
  1 PSI ≈ 0.0689 bar.

Understanding the Types of PSI: PSIG, PSIA, and PSID

The term "PSI" can be specified further to give more context:

• PSIG (Pound-force per square inch gauge): Measures pressure relative to the surrounding atmospheric pressure. This is the most common measurement, used by a standard tire gauge.

• PSIA (Pound-force per square inch absolute): Measures pressure relative to a perfect vacuum (absolute zero pressure).
  The formula is: PSIA = PSIG + local atmospheric pressure.

• PSID (Pound-force per square inch differential): Measures the difference in pressure between two separate points in a system, such as across a filter or valve.

bar to pound per square inch Conversion Table

Here are some quick reference conversions from bar (bar) to pound per square inch (psi):

This conversion in other languages

Engineering datasheets across Europe write bar to pound per square inch several different ways. The calculation is the same in every one of them.