275/45R18 Tire Size Specifications & Compatible Vehicles

Overall Diameter

704.7 mm

Section Width

275 mm

Sidewall Height

123.8 mm

Circumference

2213.9 mm

Revs/Mile

727

Rim Diameter

18"

Alternative Tire Sizes

These tire sizes are within 3% overall diameter of 275/45R18 and may be used as replacements:

275/40R19 Safe 0.3% · same width · +1" rim 285/35R20 Safe 0.4% · +10mm · +2" rim 275/35R20 Safe 0.6% · same width · +2" rim 285/40R19 Safe 0.8% · +10mm · +1" rim 255/40R20 Safe 1.0% · -20mm · +2" rim 255/45R19 Safe 1.1% · -20mm · +1" rim 255/50R18 Safe 1.1% · -20mm · same rim 255/55R17 Safe 1.1% · -20mm · -1" rim 265/50R17 Safe 1.1% · -10mm · -1" rim 265/45R18 Safe 1.3% · -10mm · same rim 295/35R20 Safe 1.4% · +20mm · +2" rim 265/40R19 Safe 1.4% · -10mm · +1" rim

Understanding 275/45R18

The tire size 275/45R18 means the tire has a section width of 275mm, an aspect ratio of 45% (the sidewall height is 45% of the width), and fits a 18-inch rim.

Sidewall Height = 275 x 0.45 = 123.8 mm
Overall Diameter = (123.8 x 2) + (18 x 25.4) = 704.7 mm
Circumference = 704.7 x π = 2213.9 mm

With an aspect ratio of 45%, this is a low-profile tire. Low-profile tires offer sharper steering response and better cornering stability, but provide a firmer ride and are more susceptible to pothole damage. They are commonly found on sport sedans and performance vehicles.

Choosing Replacement Tires

When replacing 275/45R18 tires, verify the size matches your vehicle's tire placard (typically found on the driver's door jamb or in the owner's manual). The NHTSA Tire Ratings Search tool lets you look up manufacturer load and speed ratings for specific tires.

Key factors beyond size: load index (must meet or exceed the vehicle's requirement), speed rating (must match or exceed the original specification), and seasonal type (all-season, summer, or winter) based on your driving conditions. The U.S. Tire Manufacturers Association recommends replacing all four tires at once, or at minimum in pairs on the same axle.