Auto Tire Size Calculator
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Reviewed by Calculator Editorial Team
Determine the correct tire size for your vehicle with our auto tire size calculator. Tires are sized using a standardized code that includes width, aspect ratio, construction type, diameter, and speed rating. This calculator helps you understand and calculate tire dimensions accurately.
What is Tire Size?
Tire size is a standardized code that provides information about the tire's dimensions and specifications. The code typically follows this format: WIDTH/ASPECT RATIO (CONSTRUCTION) DIAMETER SPEED RATING.
For example, a tire size of 225/45R17 91V means:
- 225 - The width of the tire in millimeters
- 45 - The aspect ratio, which is the height of the sidewall as a percentage of the tire's width
- R - The construction type (R for radial)
- 17 - The diameter of the wheel rim in inches
- 91V - The speed rating (V for 130 mph or higher)
Tire size is crucial for proper vehicle handling, safety, and compatibility with other vehicle components.
How to Read Tire Size
Reading a tire size code can be confusing if you're not familiar with the format. Here's a breakdown of the components:
- Width: The first number represents the width of the tire in millimeters.
- Aspect Ratio: The second number represents the height of the sidewall as a percentage of the tire's width.
- Construction: The letter indicates the tire's construction type (R for radial, D for diagonal, or B for bias-ply).
- Diameter: The number after the construction letter represents the diameter of the wheel rim in inches.
- Speed Rating: The final letters indicate the tire's speed rating (V for 130 mph or higher, H for 112-130 mph, etc.).
For example, a tire size of 205/55R16 88H means:
- Width: 205mm
- Aspect Ratio: 55%
- Construction: Radial (R)
- Diameter: 16 inches
- Speed Rating: 88H (up to 112 mph)
Using the Calculator
Our auto tire size calculator makes it easy to determine the correct tire size for your vehicle. Simply input the required values and click "Calculate" to get the tire size code.
The calculator uses the following formula to calculate the tire size:
For example, if you input:
- Width: 225mm
- Aspect Ratio: 45%
- Construction: Radial (R)
- Diameter: 17 inches
- Speed Rating: 91V
The calculator will output: 225/45R17 91V.
Always ensure that the tire size you choose is compatible with your vehicle's specifications.
Common Tire Sizes
Here are some common tire sizes for different types of vehicles:
| Vehicle Type | Common Tire Size |
|---|---|
| Sedan | 205/55R16, 225/45R17 |
| SUV | 235/55R17, 245/45R18 |
| Truck | 255/70R16, 275/65R17 |
| Light Truck | 265/70R17, 275/65R18 |
These are general guidelines, and the exact tire size may vary depending on the specific vehicle model and manufacturer recommendations.
Frequently Asked Questions
What does the tire size code mean?
The tire size code provides information about the tire's width, aspect ratio, construction type, diameter, and speed rating. For example, 225/45R17 91V means a tire that is 225mm wide, has a 45% aspect ratio, is radial construction, fits a 17-inch wheel, and has a speed rating of 91V (up to 130 mph).
How do I know what tire size to buy for my vehicle?
You can find the recommended tire size in your vehicle's owner's manual or by checking the current tire size on your vehicle. Our auto tire size calculator can help you determine the correct tire size based on your vehicle's specifications.
What is the difference between radial and bias-ply tires?
Radial tires have reinforced sidewalls that run perpendicular to the tread, while bias-ply tires have reinforced sidewalls that run parallel to the tread. Radial tires are more common in modern vehicles and offer better performance and handling.