**Cold inflation pressure** is the inflation pressure of tires before a car is driven and the tires (tyres) warmed up. Recommended cold inflation pressure is displayed on the owner's manual and on the placard (or sticker) attached to the vehicle door edge, pillar, glovebox door or fuel filler flap. Most passenger cars are recommended to have a tire pressure of 2.1 to 2.4 bars (210 to 240 kPa; 30 to 35 psi) when not warmed by driving.^{[1]} A 2001 NHTSA study found that 40% of passenger cars have at least one tire under-inflated by 0.4 bars (6 psi) or more.^{[2]} Drivers are encouraged to make sure their tires are adequately inflated, as under inflated tires can greatly reduce fuel economy, increase emissions, cause increased wear on the edges of the tread surface, and can lead to overheating and premature failure of the tire. Excessive pressure, on the other hand, will lead to impact-breaks, decreased braking performance, and cause increased wear on the center part of the tread surface.

Tire pressure is commonly measured in psi in the imperial and US customary systems, bar, which is deprecated but accepted for use with SI or the kilopascal (kPa), which is an SI unit.

Ambient temperature affects the cold tire pressure. Cold tire absolute pressure (gauge pressure plus atmospheric pressure) varies directly with the absolute temperature, measured in kelvin.

From physics, the ideal gas law states that *PV* = *nRT*, where *P* is absolute pressure, *T* is absolute temperature, *V* is the volume, and *nR* is constant for a given number of molecules of gas. If the volume of the tire remains constant, a 1% increase in absolute temperature results in a 1% increase in absolute pressure.

As an example, a tire is inflated to 2.2 bar (220 kPa; 32 psi) at an ambient temperature of 300 K (27 °C; 80 °F). If the absolute temperature of the air in the tire increases by 1% to 303 K (30 °C; 86 °F), the absolute pressure also increases by 1%. The absolute pressure is the sum of the ambient atmospheric pressure (approximately 1.01 bars [101 kPa; 14.7 psi] at sea level) and the gauge pressure, giving a total of 3.21 bar (321 kPa; 46.6 psi). This 3 K (3.0 °C; 5.4 °F) increase results in a change of .0321 bar (3.21 kPa; 0.466 psi). However, a similar tire inflated at an ambient temperature of 250 K (−23 °C; −10 °F) only needs to be warmed up by 2.5 K (2.5 °C; 4.5 °F) to see the same 1% increase in pressure.

Due to the temperature-dependent pressure changes, seasonal temperature fluctuations can result in appreciable changes in tire pressure.^{[1]}

(Assuming standard sea-level atmospheric pressure of 14.696 pounds per square inch or 101.33 kilopascals)^{[3]}

Pressure at 20 °C (68 °F) |
10 psi | 20 psi | 30 psi | 40 psi | 50 psi | 60 psi | 70 psi | 80 psi | 90 psi | 100 psi | |
---|---|---|---|---|---|---|---|---|---|---|---|

104 °F | 11.7 psi | 22.4 psi | 33.1 psi | 43.7 psi | 54.4 psi | 65.1 psi | 75.8 psi | 86.5 psi | 97.1 psi | 107.8 psi | 40 °C |

86 °F | 10.8 psi | 21.2 psi | 31.5 psi | 41.9 psi | 52.2 psi | 62.5 psi | 72.9 psi | 83.2 psi | 93.6 psi | 103.9 psi | 30 °C |

68 °F | 10.0 psi | 20.0 psi | 30.0 psi | 40.0 psi | 50.0 psi | 60.0 psi | 70.0 psi | 80.0 psi | 90.0 psi | 100.0 psi | 20 °C |

50 °F | 9.2 psi | 18.8 psi | 28.5 psi | 38.1 psi | 47.8 psi | 57.5 psi | 67.1 psi | 76.8 psi | 86.4 psi | 96.1 psi | 10 °C |

32 °F | 8.3 psi | 17.6 psi | 26.9 psi | 36.3 psi | 45.6 psi | 54.9 psi | 64.2 psi | 73.5 psi | 82.9 psi | 92.2 psi | 0 °C |

14 °F | 7.5 psi | 16.4 psi | 25.4 psi | 34.4 psi | 43.4 psi | 52.4 psi | 61.3 psi | 70.3 psi | 79.3 psi | 88.3 psi | −10 °C |

−4 °F | 6.6 psi | 15.3 psi | 23.9 psi | 32.5 psi | 41.2 psi | 49.8 psi | 58.4 psi | 67.1 psi | 75.7 psi | 84.3 psi | −20°C |

−22°F | 5.8 psi | 14.1 psi | 22.4 psi | 30.7 psi | 39.0 psi | 47.3 psi | 55.5 psi | 63.8 psi | 72.1 psi | 80.4 psi | −30 °C |

−40 °F | 4.9 psi | 12.9 psi | 20.8 psi | 28.8 psi | 36.8 psi | 44.7 psi | 52.7 psi | 60.6 psi | 68.6 psi | 76.5 psi | −40 °C |

Pressure at 20 °C (68 °F) |
69 kPa | 138 kPa | 207 kPa | 276 kPa | 345 kPa | 414 kPa | 483 kPa | 551 kPa | 620 kPa | 689 kPa | |

104°F | 81 kPa | 154 kPa | 228 kPa | 301 kPa | 375 kPa | 449 kPa | 522 kPa | 596 kPa | 670 kPa | 743 kPa | 40 °C |

86 °F | 75 kPa | 146 kPa | 217 kPa | 289 kPa | 360 kPa | 431 kPa | 502 kPa | 574 kPa | 645 kPa | 716 kPa | 30 °C |

68 °F | 69 kPa | 138 kPa | 207 kPa | 276 kPa | 345 kPa | 414 kPa | 483 kPa | 551 kPa | 620 kPa | 689 kPa | 20°C |

50 °F | 63 kPa | 130 kPa | 196 kPa | 263 kPa | 329 kPa | 396 kPa | 463 kPa | 529 kPa | 596 kPa | 662 kPa | 10 °C |

32 °F | 57 kPa | 122 kPa | 186 kPa | 250 kPa | 314 kPa | 378 kPa | 443 kPa | 507 kPa | 571 kPa | 635 kPa | 0 °C |

14 °F | 52 kPa | 113 kPa | 175 kPa | 237 kPa | 299 kPa | 361 kPa | 423 kPa | 485 kPa | 546 kPa | 608 kPa | −10 °C |

−4 °F | 46 kPa | 105 kPa | 165 kPa | 224 kPa | 284 kPa | 343 kPa | 403 kPa | 462 kPa | 522 kPa | 581 kPa | −20 °C |

−22 °F | 40 kPa | 97 kPa | 154 kPa | 211 kPa | 269 kPa | 326 kPa | 383 kPa | 440 kPa | 497 kPa | 554 kPa | −30 °C |

−40 °F | 34 kPa | 89 kPa | 144 kPa | 199 kPa | 253 kPa | 308 kPa | 363 kPa | 418 kPa | 473 kPa | 527 kPa | −40 °C |