Last updated: April 20, 2026
Bar to PSI Conversion
Pressure is measured in two competing unit systems that coexist across industry, engineering, and everyday life. The bar — a metric unit equal to 100,000 pascals — is used in Europe, Asia, and most of the world for everything from tyre pressure gauges to industrial hydraulic systems. PSI, or pounds per square inch, is the unit used in the United States and remains common in the UK for automotive, HVAC, and manufacturing applications.
The two units measure exactly the same physical quantity — force per unit area — using different scales, and converting between them is one of the most frequent tasks in engineering, maintenance, and technical work. One bar equals 14.5038 PSI.
This guide explains the conversion formula, walks through worked examples, provides a full reference table, and covers every major practical application where knowing your bar-to-PSI conversion matters.
What Are Bar and PSI?
The Bar — A Near-Atmospheric Metric Unit
The bar is a unit of pressure in the metric system, defined as exactly 100,000 pascals (100 kPa). It was introduced in 1909 by the British meteorologist William Napier Shaw and takes its name from the Greek word “baros,” meaning weight. Although not part of the official International System of Units (SI), the bar is accepted for use with SI and is the preferred pressure unit in most scientific, industrial, and commercial contexts outside the United States.
One bar is very close to standard atmospheric pressure — the pressure of the Earth’s atmosphere at sea level — which is 1.01325 bar. This near-equivalence to one atmosphere makes bar an intuitively useful unit: a tyre inflated to 2.5 bar is pressurised at roughly 2.5 times atmospheric pressure.
PSI — Pounds Per Square Inch
PSI stands for pounds per square inch, and it measures pressure as the force in pounds applied over an area of one square inch. It is part of the imperial and US customary system of units. One PSI equals the pressure resulting from a force of one pound-force acting uniformly on one square inch of area. Standard atmospheric pressure is 14.696 PSI — which is why 1 bar (approximately 1 atmosphere) equates to approximately 14.504 PSI.
PSI remains dominant in the United States for automotive tyre pressure, HVAC system specifications, pneumatic tools, hydraulic press ratings, and water supply pressure, and it persists in many UK industrial contexts alongside metric units.
Quick reference: 1 bar = 14.504 psi. To convert bar to psi mentally, multiply bar by 14.5. To convert psi to bar, divide psi by 14.5. For precision work, always use the full factor: 14.5038.
The Bar to PSI Formula
Exact Conversion Factor
The exact relationship between bar and PSI is derived from the SI definition of the pascal and the definition of the pound-force. One bar equals exactly 100,000 pascals, and one PSI equals exactly 6,894.757293168 pascals. Dividing 100,000 by 6,894.757293168 gives the exact conversion factor:
1 bar = 14.503773773 psi (exact to 9 decimal places)
For all practical purposes, 1 bar = 14.5038 psi is the working conversion factor used in engineering, automotive, and industrial contexts. The full formula in both directions:
PSI = Bar × 14.5038
Bar = PSI ÷ 14.5038
Why Not a Round Number?
Unlike some unit conversions — where one unit is defined as a whole multiple of another — bar and PSI arise from completely independent historical measurement traditions. The bar is based on the metric pascal, which is derived from the kilogram, meter, and second. PSI is based on the pound-force and the inch, both of which have different physical origins. Because neither unit was defined in reference to the other, the conversion factor is an irrational decimal rather than a clean integer.
This is true of most metric-to-imperial pressure conversions, and it is why a reliable conversion tool or reference table is more useful than mental arithmetic for precise work.
Worked Examples — Bar to PSI Conversions
Example 1 — Car Tyre Pressure
A vehicle manufacturer specifies a tyre pressure of 2.4 bar. A US mechanic needs this in PSI:
2.4 bar × 14.5038 = 34.809 psi
The tyre should be inflated to approximately 34.8 PSI. Most US tyre pressure gauges read to 0.5 PSI increments, so the practical target would be 35 PSI. Always check the vehicle door placard or owner’s manual — the recommended pressure is the cold inflation pressure, measured before driving when the tyre is at ambient temperature.
Example 2 — Espresso Machine Pressure
The Specialty Coffee Association specifies 9 bar as the standard extraction pressure for espresso. A technician calibrating a machine with a PSI gauge needs the equivalent reading:
9 bar × 14.5038 = 130.534 psi
The machine should register approximately 130.5 PSI at the group head during extraction. Pressures below 125 PSI (8.62 bar) typically produce under-extracted, sour espresso. Pressures above 140 PSI (9.65 bar) risk channelling and over-extraction. The PSI gauge equivalent of the 9 bar standard is one of the most practically important bar-to-PSI conversions in the food and beverage industry.
Example 3 — Industrial Hydraulic System
A hydraulic press is rated for a maximum operating pressure of 250 bar. Converting to PSI for a US safety data sheet:
250 bar × 14.5038 = 3,625.945 psi
The press operates at a maximum of approximately 3,626 PSI. This is well within the high-pressure range where hydraulic fluid injection injuries are life-threatening — a pinhole leak at this pressure can penetrate skin and tissue. Any hydraulic system operating above 1,000 PSI (68.9 bar) requires strict lockout/tagout procedures and should never be inspected or tested while pressurised.
Example 4 — Reversing the Conversion (PSI to Bar)
A US tire rated at 65 PSI maximum needs its European equivalent for an international product specification:
65 psi ÷ 14.5038 = 4.482 bar
The tyre is rated to approximately 4.48 bar maximum. European product documentation would typically round this to 4.5 bar for the specification sheet.
Bar to PSI Conversion Table — Quick Reference
| Bar | PSI | Bar | PSI |
| 0.5 bar | 7.252 psi | 7 bar | 101.526 psi |
| 1 bar | 14.504 psi | 8 bar | 116.030 psi |
| 1.5 bar | 21.756 psi | 9 bar | 130.535 psi |
| 2 bar | 29.008 psi | 10 bar | 145.038 psi |
| 2.5 bar | 36.259 psi | 15 bar | 217.557 psi |
| 3 bar | 43.511 psi | 20 bar | 290.075 psi |
| 4 bar | 58.015 psi | 50 bar | 725.189 psi |
| 5 bar | 72.519 psi | 100 bar | 1450.377 psi |
| 6 bar | 87.023 psi | 300 bar | 4351.132 psi |
Other Pressure Units — Where Bar and PSI Fit
| Unit | Full Name | 1 bar = | System | Primary Use |
| bar | Bar | 1.000 bar | Metric | Industrial, weather, European specs |
| psi | Pounds per Square Inch | 14.504 psi | Imperial / US | US automotive, HVAC, hydraulics |
| Pa | Pascal | 100,000 Pa | Metric (SI) | Scientific, aerospace, HVAC |
| kPa | Kilopascal | 100 kPa | Metric (SI) | Tire pressure outside US, medical |
| atm | Atmosphere | 0.9869 atm | Metric | Science, diving, gas cylinders |
| MPa | Megapascal | 0.1 MPa | Metric (SI) | Hydraulics, structural engineering |
| mmHg | Millimetres of Mercury | 750.06 mmHg | Medical | Blood pressure, vacuum systems |
Understanding Gauge Pressure vs. Absolute Pressure
One of the most important distinctions in pressure measurement — regardless of whether you are working in bar or PSI — is the difference between gauge pressure and absolute pressure. Absolute pressure measures pressure relative to a perfect vacuum (zero pressure). Gauge pressure measures pressure relative to the current atmospheric pressure.
Most everyday pressure gauges — tyre gauges, pressure cooker gauges, boiler gauges — measure gauge pressure. A tyre reading 2.3 bar on a gauge actually has an absolute internal pressure of 2.3 + 1.013 = 3.313 bar, because the gauge is measuring the excess above atmospheric pressure.
- Bar gauge (barg) and PSI gauge (psig) indicate gauge pressure readings
- Bar absolute (bara) and PSI absolute (psia) indicate absolute pressure readings
- At sea level: Absolute pressure = Gauge pressure + 1.01325 bar (14.696 psi)
- Always confirm which type is specified before making engineering decisions
Real-World Pressure Values — Bar and PSI Reference
| Application | Bar | PSI | Notes |
| Atmospheric pressure (sea level) | 1.013 bar | 14.696 psi | Standard reference baseline |
| Car tyre (typical) | 2.0–2.5 bar | 29–36 psi | Check vehicle door sticker for spec |
| Bicycle tyre (road) | 6.0–9.0 bar | 87–130 psi | Higher pressure reduces rolling resistance |
| Bicycle tyre (mountain) | 1.5–2.5 bar | 22–36 psi | Lower pressure improves traction |
| Espresso machine | 9 bar | 130 psi | Industry standard extraction pressure |
| Domestic water supply | 2.0–5.0 bar | 29–72 psi | Optimal range for household systems |
| Fire hose (operating) | 7.0–10.0 bar | 100–145 psi | Attack line operating pressure |
| Scuba diving cylinder | 200–300 bar | 2,900–4,351 psi | High-pressure breathing air storage |
| Hydraulic excavator system | 250–350 bar | 3,626–5,076 psi | Heavy construction equipment |
| Blood pressure (normal systolic) | 0.160 bar | 2.32 psi / 120 mmHg | Measured in mmHg clinically |
| Aeroplane cabin pressure | 0.75–0.83 bar | 10.9–12.0 psi | Equivalent to 6,000–8,000 ft altitude |
Where Bar and PSI Are Each Used
Industries That Primarily Use Bar
Bar is the dominant pressure unit in European automotive manufacturing, where tyre pressures on vehicle door stickers, wheel arch labels, and owner’s manuals are expressed in bar. European industrial machinery — compressors, pneumatic tools, injection moulding equipment, and CNC machine tool systems — is rated and calibrated in bar.
The oil and gas industry, which operates globally under European and international engineering standards, uses bar extensively for wellhead and pipeline pressures. Meteorology expresses atmospheric pressure in hectopascals (hPa) and millibars — where 1 millibar equals 0.001 bar — and weather maps and forecasts worldwide use these units. Scuba diving certifications and equipment standards use bar for cylinder pressure ratings and breathing gas partial pressures.
Industries That Primarily Use PSI
PSI dominates in the United States across virtually every pressure application. US vehicle tyre pressure is universally expressed in PSI on door placards, tyre sidewalls, and inflation equipment. The US plumbing code and home water supply standards specify pressures in PSI — residential systems typically operate at 40–80 PSI, with pressure reducing valves set to protect household fixtures from the higher pressures in the municipal supply.
American HVAC systems, refrigeration equipment, and pressure vessel codes (ASME Boiler and Pressure Vessel Code) use PSI. US pneumatic tool specifications, air compressor ratings, spray gun pressures, and nail gun operating pressures are all in PSI. In the UK, PSI remains common in automotive contexts despite the country’s general adoption of metric units.
Fields Where Both Units Appear
Several industries regularly work with both bar and PSI because their supply chains, customers, or regulatory environments span both systems. The global automotive industry — with vehicles designed in Europe, manufactured in Asia, and sold in the United States — produces technical documentation in both units. International oil and gas projects involve American operators, European engineers, and Asian manufacturers, making dual-unit literacy essential on every project.
Commercial aviation uses a mix of pressure units: cabin pressurisation is often expressed in PSI in US and UK aviation documentation, while tyre inflation for aircraft is specified in PSI in North America and sometimes bar elsewhere. Medical device manufacturers producing equipment for global markets must specify blood pressure cuffs, ventilators, and infusion pump pressures in both mmHg and kPa or PSI depending on the market.
Tips for Getting the Conversion Right
Always Identify Gauge vs. Absolute Before Converting
Converting a gauge pressure reading and an absolute pressure reading using the same factor will produce a correct numerical conversion but an incorrect physical interpretation if you do not track which type you are working with.
A tyre pressure of 35 PSI gauge (psig) converts to 2.413 bar gauge (barg). The absolute tyre pressure is 35 + 14.696 = 49.696 psia, which converts to 3.427 bara. Both conversions use the same factor — the error comes from confusing the types, not the mathematics.
Check Equipment Calibration Range Before Converting
When setting pressure equipment to a converted value, verify that the gauge or instrument can resolve the precision you need. A gauge calibrated in 1 PSI increments cannot reliably distinguish between 2.3 bar (33.4 PSI) and 2.4 bar (34.8 PSI) — a 1.4 PSI difference that is within one scale division. For critical applications — pressure testing, safety relief valve settings, medical equipment calibration — use instruments calibrated in the native unit of the specification, or use a digital gauge with adequate resolution in the converted unit.
Temperature Affects Tyre Pressure — Not the Conversion
A common source of confusion in tyre pressure work is the effect of temperature on pressure. When a tyre warms up from driving, the pressure inside increases — typically by about 4–6 PSI (0.28–0.41 bar) for every 10°C (18°F) rise in temperature. This temperature effect is a physical change in the actual tyre pressure, not a conversion error.
Always measure tyre pressure when cold (at least three hours after driving) to get a reading comparable to the manufacturer’s specification, which is always stated as a cold inflation pressure. Converting the cold pressure specification from bar to PSI and then measuring a warm tyre will give a reading that appears high — but the issue is timing, not the conversion formula.
Final Thoughts
Converting bar to psi is straightforward — multiply bar by 14.5038 to get psi, or divide psi by 14.5038 to get bar. For quick mental estimates, multiply by 14.5 (accurate to within 0.03%). The most important thing to check before converting is whether the pressure is expressed as gauge pressure or absolute pressure — because this determines the physical meaning of the converted figure. Use IntelCalculator’s free conversion tool for instant, accurate results across all pressure units including bar, psi, kPa, MPa, atm, and mmHg.
Frequently Asked Questions
How many PSI is 1 bar?
1 bar equals 14.5038 PSI. This is the standard conversion factor used across engineering, automotive, and industrial applications. For quick mental estimates, use 14.5 — the error is less than 0.03%. To convert any bar value to PSI, multiply by 14.5038. To convert PSI back to bar, divide by 14.5038.
How many bar is 1 PSI?
1 PSI equals 0.0689476 bar, which is approximately 0.069 bar. This is the inverse of the bar-to-PSI conversion: 1 ÷ 14.5038 = 0.06895. To convert any PSI value to bar, divide by 14.5038 or multiply by 0.068948.
What is 2.5 bar in PSI? (Tyre pressure)
2.5 bar equals 36.26 PSI. This is a common car tyre inflation pressure in Europe. The calculation: 2.5 × 14.5038 = 36.259 PSI, which rounds to 36 PSI in practical use. Always check the vehicle door placard for the manufacturer’s exact tyre pressure specification for your specific vehicle and load.
What is the difference between bar and psi?
Bar and PSI both measure pressure — force per unit area — but use different reference scales rooted in different measurement traditions. Bar is a metric unit equal to 100,000 pascals, close to one atmosphere of pressure. PSI is an imperial unit measuring pounds of force per square inch. One bar equals 14.504 PSI. Bar is standard in Europe and most of the world; PSI is standard in the United States and common in UK automotive applications.
What is gauge pressure vs. absolute pressure?
Gauge pressure measures pressure relative to the surrounding atmospheric pressure — it tells you how much higher the pressure is than the atmosphere. This is what most everyday gauges (tyre gauges, pressure cooker indicators) display. Absolute pressure measures pressure relative to a perfect vacuum. At sea level, absolute pressure = gauge pressure + 1.01325 bar (14.696 psi). The suffix ‘g’ (barg, psig) indicates gauge pressure; ‘a’ (bara, psia) indicates absolute. The conversion factor between bar and PSI is the same for both types.
How do I convert bar to kPa?
1 bar equals exactly 100 kilopascals (kPa). This is a round, exact conversion because both bar and kPa are metric units based on the pascal: 1 bar = 100,000 Pa = 100 kPa. To convert any bar value to kPa, simply multiply by 100. To convert kPa to bar, divide by 100. For example, 2.5 bar = 250 kPa, and 350 kPa = 3.5 bar.
What is standard atmospheric pressure in bar and PSI?
Standard atmospheric pressure — defined as the average air pressure at sea level — is 1.01325 bar or 14.6959 PSI (commonly rounded to 14.696 PSI or 14.7 PSI). This is also equal to 101.325 kPa, 760 mmHg, or 1 atmosphere (atm). The bar is approximately equal to one atmosphere but not exactly — which is why 1 bar is 14.504 PSI while 1 atm is 14.696 PSI, a difference of 0.192 PSI.
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