P305/70R15 Tire Size in Inches & Millimeters

Tire size “305/70R15” 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 P305/70R15 to inches, you must know what these numbers represent.

So let us know P305/70R15 in simple words:

First number “305” indicates the tire’s width in millimeters.
Second number “70” 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 P305/70R15 to inches, it can be concluded that the width of the tire will be approximately 12 inches ( 305 mm= 12 in), and the sidewall height will be approximately 8.4 inches (70% of 12 inches = 8.4 inches).

How to convert P305/70R15 into Inches (imperial)?

To convert tire size P305/70R15 to inches (Imperial) –

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

  • 305 millimeters/25.4 = approximately 12 inches
    So, the width of the tire is approximately 12 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 = 12 inches * 70/100 = approximately 8.4 inches
    So, the tire sidewall height is approximately 8.4 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 “P305/70R15” in inches (imperial) is approximately:

  • Width: 12 inches
  • Sidewall Height: 8.4 inches
  • Rim Diameter: 15 inches

How to convert P305/70R15 into Millimeters (metric)?

To convert the tire size P305/70R15 into millimeters (metric) –

1. Width Conversion: The first number in the tire size, “305“, represents the tire’s width in millimeters. Since it’s already in millimeters, there’s no need for conversion.

  • Width: 305millimeters

2. Aspect Ratio Calculation: The second number “70” 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 = 305 millimeters * 70 / 100 = 214 mm millimeters
    So, the tire’s sidewall height is approximately 214 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 “P305/70R15” in millimeters (metric) is approximately:

  • Width: 305 mm
  • Sidewall Height: 214 mm
  • Rim Diameter: 381 mm

Alternate Tire Size of P305/70R15 For replacement

Tire Size Overall Diameter Difference
345/55R16 30.9″ (786 mm) -2.8%
225/85R16 31″ (788 mm) -2.6%
295/65R16 31.1″ (790 mm) -2.3%
275/65R17 31.1″ (790 mm) -2.3%
255/70R17 31.1″ (790 mm) -2.3%
275/70R16 31.2″ (792 mm) -2.1%
305/60R17 31.4″ (798 mm) -1.4%
245/75R17 31.5″ (800 mm) -1.1%
285/65R17 31.6″ (802 mm) -0.9%
265/70R17 31.7″ (804 mm) -0.6%
265/75R16 31.7″ (804 mm) -0.6%
285/70R16 31.7″ (806 mm) -0.4%
235/85R16 31.7″ (806 mm) -0.4%
235/80R17 31.8″ (808 mm) -0.1%
345/55R17 32″ (812 mm) 0.4%
225/90R16 32″ (812 mm) 0.4%
255/75R17 32″ (814 mm) 0.6%
275/70R17 32.2″ (818 mm) 1.1%
375/55R16 32.2″ (818 mm) 1.1%
315/70R15 32.4″ (823 mm) 1.7%
305/65R17 32.6″ (828 mm) 2.3%
265/80R16 32.7″ (830 mm) 2.6%
285/70R17 32.8″ (832 mm) 2.8%
235/85R17 32.8″ (832 mm) 2.8%

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