215/35R18 Tire Size in Inches & Millimeters

Tire size “215/35R18” indicates your vehicle’s specifications based on tire width, aspect ratio, height, tire construction, diameter, radial and inches. These tire size numbers represent our tire sizes in both Metric (in millimeters) and Imperial (in inches) units of measurement to help find the correct tire size for your vehicle.

To convert tire size 215/35R18 to inches, you must know what these numbers represent.

So let us know 215/35R18 in simple words:

First number “215” indicates the tire’s width in millimeters.
Second number “35” refers to the aspect ratio, which is the height of the tire’s sidewall as a percentage of its width.
Third number “R18” refers to a tire that is designed to fit a 18-inch diameter rim.

Therefore, when converting the tire size 215/35R18 to inches, it can be concluded that the width of the tire will be approximately 8.5 inches ( 215 mm= 8.5 in), and the sidewall height will be approximately 3 inches (35% of 8.5 inches = 3 inches).

How to convert 215/35R18 into Inches (imperial)?

To convert tire size 215/35R18 to inches (Imperial) –

1. Width conversion: To convert it to inches, you can use a conversion factor of approximately 25.4 millimeters per inch.

  • 215 millimeters/25.4 = approximately 8.5 inches
    So, the width of the tire is approximately 8.5 inches.

2. Aspect Ratio Calculation: To calculate sidewall height in inches, you can use the tire width (from Step 1) and the aspect ratio:

  • Sidewall Height = Width (in inches) * Aspect Ratio / 100
  • Sidewall Height = 8.5 inches * 35/100 = approximately 3 inches
    So, the tire sidewall height is approximately 3 inches.

3. Rim Diameter: The “R” in the tire size stands for “radial construction” and the last number “18” indicates the rim diameter in inches. In this case, it’s already in inches.
So, the converted tire size “215/35R18” in inches (imperial) is approximately:

  • Width: 8.5 inches
  • Sidewall Height: 3 inches
  • Rim Diameter: 18 inches

How to convert 215/35R18 into Millimeters (metric)?

To convert the tire size 215/35R18 into millimeters (metric) –

1. Width Conversion: The first number in the tire size, “215“, represents the tire’s width in millimeters. Since it’s already in millimeters, there’s no need for conversion.

  • Width: 215millimeters

2. Aspect Ratio Calculation: The second number “35” is the aspect ratio, representing the tire’s sidewall height as a percentage of its width. To calculate the sidewall height in millimeters, you can use the tire’s width (from step 1) and the aspect ratio:

  • Sidewall height = Width (in millimeters) * Aspect Ratio / 100
  • Sidewall height = 215 millimeters * 35 / 100 = 75 mm millimeters
    So, the tire’s sidewall height is approximately 75 mm millimeters.

3. Rim Diameter: The “R” in the tire size stands for “radial construction” and the last number, “18” indicates the rim diameter in inches. To convert this to millimeters, you can use the conversion factor of approximately 25.4 millimeters per inch.

  • Rim diameter = 18 inches * 25.4 millimeters per inch = 457 mm millimeters
    So, the rim diameter is approximately 457 mm millimeters.

So, the converted tire size “215/35R18” in millimeters (metric) is approximately:

  • Width: 215 mm
  • Sidewall Height: 75 mm
  • Rim Diameter: 457 mm

Alternate Tire Size of 215/35R18 For replacement

Tire Size Overall Diameter Difference
165/40R18 23.2″ (589 mm) -3%
225/30R18 23.3″ (593 mm) -2.3%
195/35R18 23.3″ (593 mm) -2.3%
235/30R18 23.6″ (599 mm) -1.3%
205/35R18 23.7″ (601 mm) -1%
245/30R18 23.8″ (605 mm) -0.3%
125/60R18 23.9″ (607 mm) 0%
255/30R18 24.1″ (611 mm) 0.7%
175/45R18 24.2″ (615 mm) 1.3%
225/35R18 24.2″ (615 mm) 1.3%
265/30R18 24.3″ (617 mm) 1.6%
135/60R18 24.4″ (619 mm) 2%
225/30R19 24.4″ (619 mm) 2%
235/35R18 24.4″ (621 mm) 2.3%
205/40R18 24.4″ (621 mm) 2.3%
235/30R19 24.6″ (625 mm) 3%

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