Tire Size Calculator
Tire Size Calculator
Use this calculator to find the dimensions of a tire based on its code.
How to Read 265/70R17 Tire Size? What Does 265/70R17 Mean?
Let's break down the tire size 265/70R17 to understand what each number and letter means:
265 (Section Width)
The first number "265" represents the tire's width in millimeters, measured from sidewall to sidewall. In this case, the tire is 265 millimeters wide (approximately 10.43 inches).
70 (Aspect Ratio)
The number "70" after the forward slash is the aspect ratio or profile. This means the tire's sidewall height is 70% of its width. For a 265mm wide tire, the sidewall height would be185.50mm (approximately 7.30 inches).
R (Construction)
The letter "R" indicates this is a Radial tire, which is the most common type of tire construction today. Radial tires have layers of cord that run radially (at 90 degrees) from the center of the tire.
17 (Wheel Diameter)
The last number "17" specifies the wheel diameter in inches. This means the tire is designed to fit a 17-inch wheel. The total diameter of the tire would be the wheel size plus twice the sidewall height.
Additional Measurements
Using these numbers, we can calculate other important measurements:
- Total Tire Diameter: 17 inches (wheel) + 2 × 7.30 inches (sidewall height) = 31.61 inches
- Sidewall Height: 185.50mm or 7.30 inches (on each side)
- Circumference: Approximately 99.29 inches (based on π × total diameter)
- Revolutions per Mile: About 638 (varies slightly based on load and air pressure)
Key Tire Measurements Explained
Section Width
The width of the tire from sidewall to sidewall, measured in millimeters. This is the first number in the tire size (e.g., 265 in 265/70R17).
Aspect Ratio
The height of the tire's sidewall as a percentage of the width. A 70 aspect ratio means the sidewall height is 70% of the tire's width.
Overall Diameter
The total height of the tire when mounted on the wheel. This includes both the wheel diameter and the tire's sidewall height on both sides.
Sidewall Height
The distance from the wheel rim to the outer edge of the tire. This is calculated using the section width and aspect ratio.
Why Accurate Tire Measurements Matter
- Vehicle Performance: Tire size affects your vehicle's acceleration, braking, and handling characteristics.
- Speedometer Accuracy: Changes in tire diameter can affect your speedometer and odometer readings.
- Clearance Issues: Incorrect tire sizes may cause rubbing against your vehicle's fenders or suspension components.
- Fuel Economy: Larger or heavier tires can impact your vehicle's fuel efficiency.
Common Tire Size Conversions
Our calculator handles all the complex mathematics of tire size conversions, including:
- Converting millimeters to inches for tire width and overall diameter
- Calculating sidewall height from aspect ratio and section width
- Computing total tire circumference
- Determining revolutions per mile/kilometer
Pro Tips for Tire Sizing
✓ Check Your Vehicle's Manual: Always consult your vehicle's manual for recommended tire sizes and load ratings.
✓ Consider Your Usage: Different tire sizes can be better for specific uses (highway driving, off-road, performance, etc.).
✓ Maintain Proper Sizing: Keep front and rear tire sizes consistent unless specifically recommended otherwise by your vehicle manufacturer.
✓ Watch for Clearance: When upgrading tire size, ensure adequate clearance for steering, suspension, and body components.
Tire Size Calculator Charts by Wheel Size
Tire Size Calculator Chart for 15" Wheels
20" Tire Diameter
21" Tire Diameter
22" Tire Diameter
23" Tire Diameter
24" Tire Diameter
25" Tire Diameter
26" Tire Diameter
27" Tire Diameter
28" Tire Diameter
29" Tire Diameter
30" Tire Diameter
31" Tire Diameter
32" Tire Diameter
33" Tire Diameter
34" Tire Diameter
35" Tire Diameter
36" Tire Diameter
37" Tire Diameter
38" Tire Diameter
39" Tire Diameter
40" Tire Diameter
42" Tire Diameter
44" Tire Diameter
47" Tire Diameter
Tire Size Calculator Charts by Diameter
21" Diameter Tire Calculator Chart
13" Wheel Size
14" Wheel Size
15" Wheel Size
Tire Speed Rating
| Speed Rating | Max Speed (MPH) | Max Speed (KM/H) | Typical Use |
|---|---|---|---|
| A1 | 3 | 5 | Special use |
| A2 | 6 | 10 | Special use |
| A3 | 9 | 15 | Special use |
| B | 31 | 50 | Farm/Agricultural |
| C | 37 | 60 | Farm/Agricultural |
| D | 40 | 65 | Farm/Agricultural |
| E | 43 | 70 | Farm/Agricultural |
| F | 50 | 80 | Light Truck |
| G | 56 | 90 | Light Truck |
| J | 62 | 100 | Passenger vehicles |
| K | 68 | 110 | Passenger vehicles |
| L | 75 | 120 | Passenger vehicles |
| M | 81 | 130 | Passenger vehicles |
| N | 87 | 140 | Passenger vehicles |
| P | 93 | 150 | Passenger vehicles |
| Q | 99 | 160 | Passenger vehicles |
| R | 106 | 170 | Performance vehicles |
| S | 112 | 180 | Performance vehicles |
| T | 118 | 190 | Performance vehicles |
| U | 124 | 200 | Performance vehicles |
| H | 130 | 210 | High performance |
| V | 149 | 240 | High performance |
| W | 168 | 270 | Ultra high performance |
| Y | 186 | 300 | Ultra high performance |
| (Y) | 186 | 300 | Above 186 mph (tested) |
Note: (Y) indicates tires that have been tested above 186 mph / 300 km/h