Convert tire-pressure values between PSI, bar and kPa

The short answer

To convert tire pressure, multiply PSI by 6.894757 to get kPa, then divide kPa by 100 to get bar. To go the other way, multiply bar by 100 to get kPa, then divide kPa by 6.894757 to get PSI. For example, 30 PSI is 206.8 kPa, or 2.07 bar, and 2.2 bar is 220.0 kPa, or about 31.9 PSI.

PSI means pounds-force per square inch. Most US gauges and placards use it. kPa means kilopascal, the SI unit used on many vehicle placards and in many markets. Bar is a metric unit that equals exactly 100 kPa. The factor 6.894757 kPa per PSI comes from NIST's pressure conversion tables, which give 1 PSI as 6,894.757 pascals. NIST also lists 1 bar as 14.503774 PSI, which matches the reciprocal of the same factor.

Conversion changes only the unit, not the pressure. The correct inflation target for a vehicle still comes from that vehicle's tire placard, usually on the driver's door jamb, or from its owner's manual. The pressure molded into the tire sidewall is the tire's maximum, not the recommended running pressure.

Conversion formulas

Every formula below uses one working factor, q = 6.894757 kPa per PSI. Keep all digits until the last step, then round the final result: bar to two decimal places, and PSI and kPa to one decimal place.

q = 6.894757   (kPa per PSI)

PSI → kPa :  kPa = PSI × q
kPa → PSI :  PSI = kPa ÷ q
bar → kPa :  kPa = bar × 100
kPa → bar :  bar = kPa ÷ 100
PSI → bar :  bar = PSI × q ÷ 100   (same as PSI × 0.06894757)
bar → PSI :  PSI = bar × 100 ÷ q   (≈ bar × 14.503774)

Rounding affects how precise the result looks. One hundredth of a bar is about 0.15 PSI, so a bar value rounded to two decimals is finer than most handheld gauge markings. A value rounded to one decimal of a bar, such as 2.4 bar, can be up to about 0.7 PSI away from the exact figure. If a placard gives a whole number in one unit, you can usually set the tire to the nearest mark your gauge shows in the other unit.

Step-by-step: converting a pressure value

1. Identify the starting unit. Read the label next to the number on the placard, manual or gauge. A value of 2.2 is almost certainly bar, 220 is almost certainly kPa, and 32 is almost certainly PSI, but use the printed label rather than guessing from the size of the number.
2. Pick the formula for the unit you need from the list above.
3. Multiply or divide using the full factor, 6.894757, not a shortened version such as 6.9, and keep every intermediate digit.
4. Round only the final answer: bar to 0.01, PSI and kPa to 0.1.
5. Check the result by converting it back with the reciprocal formula. You should land within rounding of the number you started with.
6. Write down the original value, the converted value and the factor you used. That way anyone reading your note can repeat the calculation.

Worked examples

Example 1, PSI to kPa and bar: 35 PSI × 6.894757 = 241.316495 kPa. That displays as 241.3 kPa. Dividing by 100 gives 2.41316495 bar, displayed as 2.41 bar.

Example 2, bar to kPa and PSI: 2.2 bar × 100 = 220.0 kPa. Dividing by 6.894757 gives 31.908 PSI, displayed as 31.9 PSI.

Example 3, the round-trip check: convert 31.9 PSI back. 31.9 × 6.894757 = 219.94 kPa, which is 2.20 bar. That matches the 2.2 bar starting value.

These figures show how the arithmetic works. They are not inflation recommendations for any particular vehicle or tire.

Quick reference: common PSI values in kPa and bar

PSI	kPa	bar
26	179.3	1.79
28	193.1	1.93
30	206.8	2.07
32	220.6	2.21
33	227.5	2.28
35	241.3	2.41
36	248.2	2.48
40	275.8	2.76
41	282.7	2.83
44	303.4	3.03
50	344.7	3.45
65	448.2	4.48
80	551.6	5.52

Some of the most searched values in short form: 26 PSI is about 1.79 bar, 30 PSI about 2.07 bar, 33 PSI about 2.28 bar, 36 PSI about 2.48 bar, 41 PSI about 2.83 bar, 50 PSI about 3.45 bar and 65 PSI about 4.48 bar. The higher values in the table are more common on light-truck, trailer and other load-rated tires than on typical passenger cars. Whether any of them applies to your tires depends on the vehicle placard and the tire's load rating.

Quick reference: common bar and kPa values in PSI

bar	kPa	PSI
1.8	180	26.1
2.0	200	29.0
2.2	220	31.9
2.3	230	33.4
2.4	240	34.8
2.5	250	36.3
2.8	280	40.6
3.0	300	43.5
3.5	350	50.8

Printable conversion worksheet

If you want a worksheet to keep in the garage or glovebox, copy the layout below into a document and print it, or save it as a PDF. Fill in one row for each axle or tire position, using the values from your own placard.

TIRE PRESSURE CONVERSION WORKSHEET
Factor: q = 6.894757 kPa per PSI   |   1 bar = 100 kPa
Rounding: bar to 0.01, PSI and kPa to 0.1 (final result only)

Position     | Placard value | Unit | kPa      | bar    | PSI    | Back-check OK?
-------------|---------------|------|----------|--------|--------|---------------
Front        |               |      |          |        |        |
Rear         |               |      |          |        |        |
Spare        |               |      |          |        |        |
Loaded/other |               |      |          |        |        |

PSI → kPa: × 6.894757     kPa → PSI: ÷ 6.894757
kPa → bar: ÷ 100          bar → kPa: × 100
PSI → bar: × 0.06894757   bar → PSI: × 14.503774

Using the converted number at the pump

1. Find the target on the vehicle's tire placard or in the owner's manual. Note any separate front, rear, spare or full-load values.
2. Convert the target into whichever unit your gauge or air machine displays.
3. Check pressure when the tires are cold, meaning before driving or after the vehicle has been parked for a while. Driving warms the tires and raises the reading.
4. Add or release air until the gauge matches the converted target, then recheck.
5. Stop and have the tire inspected by a tire professional if it will not hold pressure, loses pressure again quickly, or shows cuts, bulges or exposed cords. Converting units cannot fix a damaged tire.