305/30 R18 tires' overall diameter is 25.2 inches, tire width is 12 inches, the tire can be mounted on 18 inches wheel and the circumference is 79.2". With that parameters, we can calculate that it will take approximately 800 revolutions per mile.
So the closest metric tire size of 305/30R18 existing size in inches is 28x12.00R18, which is 11.11% taller and 0% wider.
You can use our handy tire size calculator to compare 305/30 R18 vs 28x12.00R18.
For each tire size there often there are several wheel sizes. You can't put too wide tires on narrow rims or vice versa. Here is what size of the wheels your vehicle needs for 305/30 R18 tires:
Rim diameter x rim width
| Parameter | Meaning |
|---|---|
| 305 | The first number shows that the tire has a section width of 305 mm or approximately 12 inches. |
| 30 | The second number is the aspect ratio or sidewall height. In this case, it is 30%. It shows the height of the tire from the ground to the rim edge or the height of the tire's cross-section which is 30% of the width or ~ 92mm |
| R18 | The letter R means this tire is radial. Most of all tires nowadays are radial. The number is the tire diameter in inches. It means that the tire will fit 18-inch wheels |
If you want to know more about how to decipher information inscribed on your tires, including aspects such as the tire height, tire width, and the diameter of the wheel, this guide provides an in-depth look at how to read a tire sidewall. These measurements can reveal a wealth of information about your tire's specifications and suitability for your vehicle. Mastering these details will allow you to make informed decisions when buying or replacing your tires.