Understanding Your Current Tire Size
Knowing your Jeep's tire size can be essential information when it comes time to replace that rubber, or even if you ever decide to change wheels. And while a stock tire size is imprinted right inside the driver side B pillar, you may not know what if have if you are not the original owner.
Put simply, the first number is the tire's width in millimeters, the second number is the tire's aspect ratio, which is the height of the sidewall as a percentage of the width, and the third number is the tire's diameter in inches.
Here is a more detailed breakdown on what each number means and how it affects your tire.
First, the sidewall of your tire contains all the information needed to understand everything about that specific tire. All tires are required to have this information, regardless of the manufacturer brand name.
Now, this information could read in a few different ways. For example, it could simply say 35x12.5 R17, or it may show as P265 75 R15. If it is the first listing, then here is the breakdown. That first number is your tire size at 35", and then the second number tells you the tire width at 12.5". That third reading is the tire type as radial and diameter as 17".
The second listing is a metric set up, and is what is more common on factory-type sized tires. From left to right, the P indicates a passenger tire while 265 indicates the tires width in millimeters. That 75 is the tire's aspect ratio and simply means the tire's height is equal to 75 percent of its width. Finally, like the first set of numbers, that R15 means it is a radial tire and has a 15" diameter.
For those who have the metric reading on their tires, you can simply plug that into the conversion calculator to determine the tire size, or find that corresponding reading on one of the below conversion charts.
Metric to Standard Conversion
Enter the metric size (i.e. 285/75 R17)
15-inch Wheel Conversion Chart
| Metric | Standard |
|---|---|
| 215/75/15 | 27.7"x 8.5" |
| 225/70/15 | 27.4"x 8.9" |
| 225/75/15 | 28.3"x 8.9" |
| 235/75/15 | 29.0"x 9.3" |
| 245/75/15 | 29.5"x 9.6" |
| 255/75/15 | 30.0"x 10.0" |
| 265/75/15 | 30.6"x 10.4" |
16-inch Wheel Conversion Chart
| Metric | Standard |
|---|---|
| 205/85/16 | 29.7"x 8.1" |
| 215/75/16 | 28.7"x 8.5" |
| 225/70/16 | 28.4"x 8.9" |
| 225/75/16 | 29.2"x 8.9" |
| 235/70/16 | 29.0"x 9.3" |
| 235/85/16 | 31.7"x 9.3" |
| 245/70/16 | 29.5"x 9.6" |
| 245/75/16 | 30.5"x 9.6" |
| 255/70/16 | 30.0"x 10.0" |
| 265/70/16 | 30.6"x 10.4" |
| 265/75/16 | 31.6"x 10.4" |
| 275/70/16 | 31.2"x 10.8" |
| 285/75/16 | 32.8"x 11.2" |
| 295/75/16 | 33.4"x 11.6" |
| 305/70/16 | 33.0"x 12.2" |
| 315/75/16 | 34.8"x 12.4" |
| 375/55/16 | 32.8"x 15.5" |
| 395/70/16 | 37.9"x 16.0" |
17-inch Wheel Conversion Chart
| Metric | Standard |
|---|---|
| 245/70/17 | 30.6"x 9.8 |
| 265/70/17 | 31.6"x 10.7 |
| 285/70/17 | 33.0"x 11.5 |
| 315/70/17 | 34.4"x 12.4 |
18-inch Wheel Conversion Chart
| Metric | Standard |
|---|---|
| 275/65/18 | 32.1"x 11.0 |
| 375/50/18 | 33.0"x 15.4 |
| 325/60/18 | 33.2"x 13.3 |
| 325/65/18 | 34.8"x 13.5 |
| 305/70/18 | 35.0"x 12.2 |
| 375/60/18 | 35.7"x 15.5 |
| 395/65/18 | 37.8"x 15.7 |
20-inch Wheel Conversion Chart
| Metric | Standard |
|---|---|
| 325/50/20 | 33.0"x 13.2" |
Metric measurement example: 225/70R15
- 225 = Section width in millimeters
- 70 = Aspect ratio (ratio of section height to section width)
- R15 = Rim diameter
- R = Radial Construction, B = Bias Construction, D = Bias Belted Construction
Calculations for Measurements
- Tire Width: Section width divided by 25.4 (Ex: 225 / 25.4 = 8.86")
- Section Height: Tire width times aspect ratio (Ex: 8.86" x 70% = 6.20")
- Overall Diameter: Section height times 2 plus rim diameter (Ex: (6.20" x 2) + 15 = 27.40")
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