Tire Size Comparison Calculator
Compare two tire sizes side by side. See differences in overall diameter, width, sidewall height, circumference, revolutions per mile, and speedometer correction โ with a visual size comparison.
Enter Tire Sizes
๐ด Tire 1 (Original / Stock)
๐ข Tire 2 (New / Comparison)
Visual Size Comparison
Comparison Results
| Measurement | Tire 1 | Tire 2 | Difference |
|---|
Speedometer Correction
With Tire 2, when your speedometer reads a given speed, your actual speed will be:
| Speedo Reads | Actual Speed | Difference |
|---|
Recommended Gear
Frequently Asked Questions
How do I read a tire size like 265/70R17?
The first number (265) is the section width in millimeters โ the widest point of the tire from sidewall to sidewall. The second number (70) is the aspect ratio โ the sidewall height expressed as a percentage of the width. So the sidewall is 70% of 265 mm = 185.5 mm tall. The "R" means radial construction (virtually all modern tires). The last number (17) is the rim diameter in inches. To get the overall tire diameter, add the rim size (converted to mm) plus two sidewall heights.
How much bigger can I go without rubbing?
A general guideline is to stay within 3% of your original tire's overall diameter. Going beyond that increases the risk of rubbing on fenders, suspension components, or inner fender liners โ especially at full steering lock or when going over bumps. Factors that affect clearance include wheel offset, lift height, and specific vehicle geometry. Some trucks and SUVs can handle larger increases with a leveling kit or lift.
Will changing tire size affect my speedometer?
Yes. Your speedometer is calibrated for the original tire size. A taller tire covers more ground per revolution, so your speedometer will read slower than your actual speed (you're going faster than it says). A shorter tire makes it read faster than actual. Use the speedometer correction table above to see exact differences. Many vehicles can be recalibrated with a dealer flash or aftermarket tuner.
What's the difference between metric and flotation tire sizes?
Metric sizes (like 265/70R17) list width in millimeters, aspect ratio as a percentage, and rim size in inches. Flotation sizes (like 33x12.50R15) list overall diameter first (33 inches), then width (12.50 inches), then rim diameter (15 inches). Flotation sizing is common on off-road and light truck tires. Both describe the same physical properties โ just different notation systems. This calculator handles both formats.
Does tire size affect fuel economy?
Yes. Larger and wider tires increase rolling resistance, rotational mass, and aerodynamic drag, all of which reduce fuel economy. Expect roughly a 1โ2 MPG decrease when going up one or two sizes on a truck or SUV. Heavier all-terrain or mud-terrain tread patterns make it worse. The tradeoff is better traction, ground clearance, and appearance.
How are revolutions per mile calculated?
Revolutions per mile = 63,360 รท (ฯ ร tire diameter in inches). One mile is 63,360 inches. The tire's circumference (ฯ ร diameter) is the distance covered in one revolution. Dividing gives you how many times the tire must rotate to cover a mile. A larger tire has fewer revolutions per mile, which is why it throws off your speedometer and odometer readings.