Convert bar to psi bars ↔ pounds per square inch Free Online Secure
Type a value in bars and read it in pounds per square inch at once. The factor is exact by definition, the arithmetic happens in your browser, and nothing is sent anywhere.
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Common values — Convert bar to psi (bars ↔ pounds per square inch)
| bar | psi |
|---|---|
| 1 | 14.503773773 |
| 2 | 29.007547546 |
| 3 | 43.5113213191 |
| 5 | 72.5188688651 |
| 10 | 145.03773773 |
| 20 | 290.07547546 |
| 50 | 725.188688651 |
| 100 | 1450.3773773 |
Where these units come from
Pressure is force spread over an area, and the SI unit says so plainly: a pascal is one newton on one square metre. It is a very small amount — ordinary air presses on us with about 101,325 of them — so practical work uses multiples. The bar was invented in the 1900s by the meteorologist Vilhelm Bjerknes as a round 100,000 pascals, close enough to sea-level air pressure to be a convenient yardstick, and it stuck in weather, in diving and in tyre gauges across Europe. The pound per square inch came the other way, straight from the pound and the inch, and it still rules American industry and the garage forecourt.
Where you meet them
Tyres are the place most people meet pressure, quoted in bar in Europe and in psi in the United States and Britain. Beyond that: weather maps in hectopascals, which are the same number as millibars; boilers, hydraulics and compressed air in bar; gas cylinders, hoses and engine testing in psi; and vacuum work in pascals, where the small unit is finally the right size.
Questions people ask
How is a bar related to atmospheric pressure?
A bar is exactly 100,000 pascals, which is close to the atmosphere but not equal to it: standard atmospheric pressure is 1.01325 bar. Under water the pressure rises by roughly one bar for every ten metres of depth, so a diver at 30 metres feels about four bar in total, counting the air above.
Is tyre pressure measured from zero or from the air around it?
From the air around it. A gauge reads gauge pressure — the amount above the surrounding atmosphere — so a tyre at 2.2 bar actually holds about 3.2 bar of absolute pressure. This page converts the numbers as given, without assuming one or the other, so a gauge reading in one unit converts to a gauge reading in the next.
Is the answer exact?
Where both units are defined in terms of one another by whole numbers, yes — the page says so above the figure, and the only rounding is in how many digits are shown. Where the ratio has no finite decimal, the page shows twelve significant digits and says the relation is approximate rather than pretending otherwise.
Does anything I type leave my device?
No. The arithmetic runs in your browser; nothing is uploaded and there is no server to upload it to. Load the page once and it keeps working with the network switched off.
Bar to psi: pressure under the sea, in the cup and in the workshop
A diver reads a tank at 200 bar, an espresso machine pulls a shot at 9 bar, a pressure washer is rated at 150 bar, and an American manual lists all of them in pounds per square inch. Pressure is the quantity where the two unit systems collide most often, because a single mistake can lead to an overfilled cylinder or a weak hose. To convert bar to psi, multiply by 14.5038: 9 bar is 130.5 psi, 100 bar is 1,450 psi and 200 bar is 2,901 psi. The calculator above does the multiplication as you type, and the sections below turn the numbers into everyday and industrial settings.
The page gives the rule with worked examples, a profile of each unit, a comparison and many cases from diving, brewing, plumbing and engineering, followed by the usual mistakes. The calculation runs in your browser and nothing you type is sent anywhere. For safety-critical equipment, always follow the manufacturer's rating.
How to convert bar to psi: multiply by 14.5038
The rule
One bar is 100,000 pascals and one psi is 6,894.757 pascals, so a bar contains 100,000 / 6,894.757 = 14.50377 psi. To convert bar to psi, multiply the pressure in bar by 14.5038. That makes 1.8 bar equal to 26.1 psi, 3 bar equal to 43.5 psi and 350 bar equal to 5,076 psi. To go back, multiply psi by 0.06895.
Worked examples
A car tyre at 2.4 bar holds 34.8 psi. A road bicycle tyre at 7 bar holds 101.5 psi. A scuba cylinder filled to 200 bar holds 2,901 psi, and a pressure washer working at 150 bar delivers 2,176 psi.
How exact the factor is
The factor 14.50377 follows from two definitions and has no hidden rounding. For everyday uses, 14.5 is enough, with an error under 0.03 per cent.
A quick sanity test
The figure in psi is nearly fifteen times the figure in bar. If a “convert bar to psi” calculation gave a smaller number than you started with, you used the factor for the opposite direction.
The bar
The practical metric unit
The bar equals 100,000 pascals, close to ordinary atmospheric pressure, which is 1.013 bar. It is the usual unit on European gauges, in cylinder markings, in plumbing and in industrial specifications.
Where it appears
Cylinders, compressors, boilers, hydraulics, brewing and diving.
Psi
The American pressure unit
Psi stands for pound-force per square inch. It is the unit on American gauges, tank ratings and equipment manuals. A gauge calibrated in psi usually carries a second scale in bar or kPa.
Where it appears
Pumps, gauges, American tank and hose ratings, and tyre guides.
Bar against psi
One bar is 14.5 psi, so the figure in psi is nearly fifteen times larger. A pressure of 2 bar is 29 psi and one of 10 bar is 145 psi. Both measure the same pressure; only the size of the unit differs.
The conversion is exact and hides no rounding. The trap is direction: from bar to psi the number grows.
Where the conversion shows up
Diving cylinders
European cylinders are filled to 200 or 232 bar, which is 2,901 or 3,365 psi. American cylinders are rated at 3,000 psi, which is 207 bar, or 3,442 psi, which is 237 bar for high-pressure models. A diver abroad who confuses "3,000" with 300 bar would be dangerously wrong. A “convert bar to psi” calculation before any fill prevents that.
Espresso machines
A machine extracts coffee at 9 bar, 130.5 psi, a standard in the industry. Pump gauges on machines sold in the United States show 130 psi. Brewers who experiment with 6 bar, 87 psi, or 12 bar, 174 psi, change the flow and the taste.
Pressure washers and hydraulics
Domestic washers work at 100 to 150 bar, 1,450 to 2,176 psi. Professional ones exceed 200 bar, 2,901 psi. Hydraulic systems run at 200 to 350 bar, 2,901 to 5,076 psi. A hose labelled 5,000 psi withstands 345 bar.
Breathing air in a cylinder
A 12-litre cylinder at 200 bar holds 2,400 litres of free air, which at a dive of 10 metres, where the pressure is 2 bar, lasts for around 100 minutes at a modest breathing rate of 12 litres per minute at the surface. In psi the same cylinder reads 2,901. Dive computers show the reading in bar or in psi, according to the market.
Tyre pressure by vehicle
A car runs on 2.0 to 2.5 bar, 29 to 36 psi, a motorcycle on 2.0 to 2.9 bar, 29 to 42 psi, a truck on 8 to 9 bar, 116 to 131 psi, and a tractor on as little as 0.8 to 1.8 bar, 12 to 26 psi, to protect the soil. Always use the vehicle's own placard.
Hot and cold tyres
Tyre pressure should be checked cold. Driving warms the air in the tyre and adds 0.2 to 0.3 bar, 3 to 4 psi. A tyre at 2.2 bar, 31.9 psi, at 15 °C reads about 2.35 bar, 34 psi, at 35 °C. Bleeding a warm tyre down to the placard value leaves it under-inflated when it cools.
Bicycle tyres
A road tyre runs on 6 to 8 bar, 87 to 116 psi, a mountain-bike tyre on 1.5 to 2.5 bar, 22 to 36 psi, and a city bike on 3 to 5 bar, 44 to 73 psi. Floor pumps display both scales, and a “convert bar to psi” calculation is only needed when one scale is missing.
Sports balls
A football is inflated to 0.6 to 1.1 bar, 8.7 to 16 psi, a basketball to 0.5 to 0.6 bar, 7 to 9 psi, and a volleyball to about 0.3 bar, 4.3 psi. With such low values a tenth of a bar is 1.5 psi, so use at least one decimal place.
Pressure cookers
A pressure cooker works at 1 bar above atmospheric, 14.5 psi, raising the boiling point to about 120 °C. Food cooks two to three times faster. American recipes quote the pressure in psi, European ones in bar, and the pot's valve is set to match.
Gauge and absolute pressure
Most gauges show pressure relative to the air around them, called gauge pressure. Absolute pressure is greater by 1.013 bar or 14.7 psi. The notations bar(g) and bar(a), or psig and psia, tell them apart. For tyres the gauge value is the one that counts.
The mental shortcut
To convert bar to psi in your head, multiply by 14 and add 3 per cent. For 2.2 bar: 30.8 plus 0.9 gives 31.7, close to 31.9. For 3 bar: 42 plus 1.3 gives 43.3, against 43.5. For tyre work the error is negligible.
Spreadsheet formulas
To convert bar to psi in a spreadsheet, put the pressures in bar in column A and type =A2*14.5038 in column B. For the reverse, =B2/14.5038. A third column with =A2*100000 gives pascals for cross-checking.
Rounding and precision
Workshop gauges are accurate to about 0.1 bar, which is 1.5 psi. For a tyre, quoting one decimal is enough: 2.2 bar is 31.9 psi. For high-pressure cylinders, rounding to tens of psi is acceptable. Match the number of digits to the accuracy of the gauge.
Landmarks to memorise
1 bar is 14.5 psi. 2 bar is 29 psi. 2.5 bar is 36 psi. 3 bar is 43.5 psi. 5 bar is 72.5 psi. 10 bar is 145 psi. 100 bar is 1,450 psi. To convert bar to psi by eye, scale from these values.
Pressure under water
Every 10 metres of sea water adds almost 1 bar, or 14.5 psi. At 30 metres the absolute pressure is 4 bar, 58 psi, and at 40 metres 5 bar, 72.5 psi. The deepest part of the ocean, at 10,900 metres, has about 1,086 bar, which is 15,750 psi.
Reference ladder
1.5 bar is 21.76 psi. 1.8 bar is 26.11 psi. 2.4 bar is 34.81 psi. 2.8 bar is 40.61 psi. 3.5 bar is 50.76 psi. 6 bar is 87.02 psi. 8 bar is 116.03 psi. 12 bar is 174.05 psi. 20 bar is 290.08 psi. A ladder like this makes checking easy.
Checking by reversing
To check a “convert bar to psi” calculation result, multiply the answer by 0.06895. If 2.2 bar became 31.91 psi, then 31.91 times 0.06895 returns 2.2. A second test is size: the number in psi should be nearly fifteen times larger.
Link to kPa and atmospheres
One bar is 100 kPa, 0.987 atmospheres, 750 mmHg and about 1.02 kgf/cm². A pressure of 2.2 bar is 220 kPa, 2.17 atmospheres and 31.9 psi. Older gauges often show kgf/cm², very close to bar.
A worked example
A driver buys a compressor in the United States with a psi gauge and wants a tyre at 2.3 bar. The calculation is 2.3 × 14.5038 = 33.4 psi. The driver stops at 33 to 34 psi and checks with a gauge in bar. The result should be 2.3 ± 0.05 bar.
Force on a surface
A pressure of 2.2 bar means a force of 22 newtons on every square centimetre, nearly 2.2 kilograms-force. On a contact patch of 150 cm² the total is 3,300 newtons, about 336 kilograms, the load carried by one wheel of a small car.
Cold weather
As temperatures drop, tyre pressure drops with them: about 0.08 bar, 1.1 psi, for every 10 degrees of cooling on a tyre at 2.2 bar. A warning light that comes on at the first frost need not mean a leak. Check with a gauge, in the unit of your pump.
Spare wheels
Compact spare wheels often need 4.2 bar, 61 psi, much more than a normal tyre, so that a small tyre can carry the same load. An American pump shows 61 psi for 4.2 bar. A driver who forgets the conversion could inflate the spare to half the correct value.
Monitoring systems
Tyre-pressure monitors warn when pressure falls 20 to 25 per cent below the recommended value. For a tyre at 2.2 bar, 31.9 psi, the warning comes near 1.65 bar, 23.9 psi. The display may be in bar or psi, depending on the market the car was built for.
Three scales on one gauge
Good gauges carry bar, kPa and psi. Reading 2.2 bar, you see 220 kPa and 32 psi at the same place on the dial. If your gauge has only psi, convert each placard value once and write it on a card in the glove box.
Two routes to one result
You can convert bar to psi directly with 14.5038, or through pascals: multiply by 100,000 and divide by 6,894.757. If the results differ, a digit was copied wrongly.
The espresso shot
Water at 93 °C is forced through ground coffee at 9 bar. The pressure drives the water through the puck in about 25 to 30 seconds and extracts the oils that form crema. A reading of 130 psi on an American gauge corresponds to the correct 9 bar. Machines that run at higher pressure risk channelling in the puck.
Weather charts in hectopascals
Weather maps use hectopascals, where 1 hPa is 0.001 bar. A standard sea-level pressure of 1,013 hPa is 1.013 bar, 14.7 psi. A deep storm at 960 hPa is 0.96 bar, 13.9 psi, and the record low of a tropical cyclone near 870 hPa is 0.87 bar, 12.6 psi. Converting from hPa to psi goes through bar.
Blood pressure
Blood pressure is measured in millimetres of mercury. A normal systolic value of 120 mmHg is 0.16 bar or 2.3 psi, and a diastolic 80 mmHg is 0.107 bar, 1.55 psi. The numbers are tiny compared with a tyre, which shows how different the pressure scales of biology and engineering are.
Vacuum
A vacuum pump that reaches 1 millibar, 0.001 bar, leaves 0.0145 psi. Laboratory vacuum is often quoted in mbar or torr, while American equipment lists inches of mercury or psi. To convert bar to psi for a vacuum gauge, remember that a reading of 0 bar absolute is a perfect vacuum and 1.013 bar absolute is open air.
Home water pressure
Mains water in a town runs at 3 to 5 bar, 43 to 73 psi. A domestic boiler circuit sits at 1.5 bar, 21.8 psi, and an expansion vessel is pre-charged to 1 bar, 14.5 psi. American plumbing manuals use psi throughout, with 40 to 80 psi as the usual range for a house.
Gas bottles
Propane at 20 °C has a vapour pressure of about 8.4 bar, 122 psi. A regulator reduces it to 0.03 bar, 0.44 psi, at the burner. The pressure in a bottle depends on temperature only as long as liquid remains, so a gauge does not show how much gas is left.
Fire extinguishers
A carbon-dioxide extinguisher holds about 57 bar at 20 °C, which is 827 psi, and a dry-powder one holds around 15 bar, 218 psi. Labels carry bar in Europe and psi in the United States. Both must agree at the periodic inspection.
Common-rail diesel
A modern diesel engine injects fuel at 1,600 to 2,500 bar, which is 23,200 to 36,300 psi. Numbers this large are quoted in bar even in America, where psi would give five digits. The extreme pressure atomises the fuel into a fine mist.
Altitude and the atmosphere
At sea level air presses with 1.013 bar, 14.7 psi. At 3,000 metres it is 0.70 bar, 10.1 psi, and on Everest around 0.33 bar, 4.8 psi. An airliner cabin is held near 0.75 to 0.80 bar, 10.9 to 11.6 psi, equivalent to 2,000 to 2,500 metres.
Industrial compressed air
A workshop compressor supplies 8 to 10 bar, 116 to 145 psi. A pneumatic tool is designed for 6.3 bar, 91 psi, which in America is simply 90 psi. If your compressor gauge is in bar and the tool in psi, a “convert bar to psi” calculation tells you whether the regulator is set correctly.
More values for convert bar to psi
A longer list of conversions
If the value you need is not in the first list, these further conversions may be close enough to read off directly:
- 0.1 bar = 1.45038 psi
- 0.5 bar = 7.25189 psi
- 3 bar = 43.5113 psi
- 4 bar = 58.0151 psi
- 7 bar = 101.526 psi
- 15 bar = 217.557 psi
- 20 bar = 290.075 psi
- 75 bar = 1,087.78 psi
- 200 bar = 2,900.75 psi
- 500 bar = 7,251.89 psi
- 2,000 bar = 29,007.5 psi
- 10,000 bar = 145,038 psi
Common slips with a “convert bar to psi” calculation
Multiplying by 0.06895
From bar to psi the number grows. If 2.2 bar became 0.15, you used the factor for the other direction.
Reading the wrong scale
A gauge that shows 32 may be in psi or in bar. In psi, that is 2.2 bar. In bar, it would be a lethal pressure for a tyre. Always read the scale on the dial.
Gauge versus absolute pressure
Tyre pressure is gauge pressure. Do not add 14.7 psi or 1 bar to what you read.
Short answers
How do I convert bar to psi?
Multiply the bar figure by 14.5038.
How many psi is 2.2 bar?
31.91 psi.
How many psi is 200 bar?
2,900.8 psi.
How many bar is 1 psi?
0.06895 bar.
Does my number leave my device?
No, the calculation runs in your browser.
More pages and a wrap-up
For other pressure conversions see Convert bar to Pa, Convert kPa to psi, Convert psi to kPa, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C, Convert cm³ to L, Convert km/h to Mach. The reverse direction is Convert psi to bar.
In short, a “convert bar to psi” calculation comes down to multiplying by 14.5038 and writing the unit beside the answer. Your number is computed locally, with no account and no upload.