165/55R15 Tire Size in Inches & Millimeters

Tire size “165/55R15” 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 165/55R15 to inches, you must know what these numbers represent.

So let us know 165/55R15 in simple words:

First number “165” indicates the tire’s width in millimeters.
Second number “55” refers to the aspect ratio, which is the height of the tire’s sidewall as a percentage of its width.
Third number “R15” refers to a tire that is designed to fit a 15-inch diameter rim.

Therefore, when converting the tire size 165/55R15 to inches, it can be concluded that the width of the tire will be approximately 6.5 inches ( 165 mm= 6.5 in), and the sidewall height will be approximately 3.6 inches (55% of 6.5 inches = 3.6 inches).

How to convert 165/55R15 into Inches (imperial)?

To convert tire size 165/55R15 to inches (Imperial) –

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

  • 165 millimeters/25.4 = approximately 6.5 inches
    So, the width of the tire is approximately 6.5 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 = 6.5 inches * 55/100 = approximately 3.6 inches
    So, the tire sidewall height is approximately 3.6 inches.

3. Rim Diameter: The “R” in the tire size stands for “radial construction” and the last number “15” indicates the rim diameter in inches. In this case, it’s already in inches.
So, the converted tire size “165/55R15” in inches (imperial) is approximately:

  • Width: 6.5 inches
  • Sidewall Height: 3.6 inches
  • Rim Diameter: 15 inches

How to convert 165/55R15 into Millimeters (metric)?

To convert the tire size 165/55R15 into millimeters (metric) –

1. Width Conversion: The first number in the tire size, “165“, represents the tire’s width in millimeters. Since it’s already in millimeters, there’s no need for conversion.

  • Width: 165millimeters

2. Aspect Ratio Calculation: The second number “55” 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 = 165 millimeters * 55 / 100 = 91 mm millimeters
    So, the tire’s sidewall height is approximately 91 mm millimeters.

3. Rim Diameter: The “R” in the tire size stands for “radial construction” and the last number, “15” 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 = 15 inches * 25.4 millimeters per inch = 381 mm millimeters
    So, the rim diameter is approximately 381 mm millimeters.

So, the converted tire size “165/55R15” in millimeters (metric) is approximately:

  • Width: 165 mm
  • Sidewall Height: 91 mm
  • Rim Diameter: 381 mm

Alternate Tire Size of 165/55R15 For replacement

Tire Size Overall Diameter Difference
185/45R15 21.5″ (547 mm) -2.8%
165/50R15 21.5″ (547 mm) -2.8%
245/35R15 21.8″ (553 mm) -1.8%
215/40R15 21.8″ (553 mm) -1.8%
165/45R16 21.8″ (554 mm) -1.6%
215/35R16 21.9″ (556 mm) -1.2%
125/70R15 21.9″ (557 mm) -1.1%
195/45R15 21.9″ (557 mm) -1.1%
175/50R15 21.9″ (557 mm) -1.1%
195/40R16 22.1″ (562 mm) -0.2%
165/40R17 22.2″ (564 mm) 0.2%
205/45R15 22.2″ (565 mm) 0.4%
155/60R15 22.3″ (567 mm) 0.7%
185/50R15 22.3″ (567 mm) 0.7%
115/70R16 22.4″ (568 mm) 0.9%
135/60R16 22.4″ (568 mm) 0.9%
145/65R15 22.4″ (569 mm) 1.1%
205/40R16 22.4″ (570 mm) 1.2%
135/70R15 22.5″ (571 mm) 1.4%
165/50R16 22.5″ (572 mm) 1.6%
175/55R15 22.6″ (573 mm) 1.8%
275/35R15 22.6″ (573 mm) 1.8%
215/45R15 22.6″ (575 mm) 2.1%
195/50R15 22.7″ (577 mm) 2.5%
245/40R15 22.7″ (577 mm) 2.5%
215/40R16 22.8″ (578 mm) 2.7%
245/35R16 22.8″ (578 mm) 2.7%
165/60R15 22.8″ (579 mm) 2.8%

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