Tire Calculator – Compare Tire Sizes Easily
The Tire Calculator helps you compare different tire sizes to find the perfect fit for your car, truck, or SUV. Calculate changes in diameter, width, sidewall height, and revolutions per mile when upgrading or replacing tires.
How to Use the Tire Calculator
Enter:
- Your current tire size (e.g., 205/55R16)
- Your new tire size for comparison (e.g., 215/50R17)
The calculator instantly shows the difference in overall diameter, sidewall height, circumference, and speedometer impact.
How It Works
Tire size is calculated using this formula:
- Sidewall Height: (Width × Aspect Ratio) / 100
- Diameter: (2 × Sidewall Height) + Wheel Diameter
- Circumference: π × Diameter
Example
Original: 205/55R16
→ Sidewall: (205 × 55) / 100 = 112.75 mm
→ Diameter: (2 × 112.75) + 406.4 mm = 631.9 mm (~24.9 inches)
New: 215/50R17 → Compare for fit & speed difference.
Common Use Cases
- Comparing OEM vs aftermarket tires
- Choosing low-profile performance tires
- Ensuring correct speedometer reading
- Finding safe tire upgrades for clearance
- Checking compatibility with rims
Why Use a Tire Calculator?
Picking the wrong tire size can affect your speedometer, fuel economy, and vehicle safety. This calculator helps you choose the right fit without guesswork.
Frequently Asked Questions (FAQs)
Does changing tire size affect my speedometer?
Yes — bigger or smaller diameter tires can make your speedometer read faster or slower.
Can I use different size rims?
Yes, but the overall diameter should stay within 3% of the original to avoid issues.
Are wider tires better?
Wider tires may offer more grip but can affect fuel economy and clearance.
What does the aspect ratio mean?
It’s the sidewall height expressed as a percentage of the tire width.
Is there a legal limit for tire size changes?
Some regions have regulations — always check local laws before modifying tire sizes.
Related tools: Car Calculator, MPG Calculator, Distance Calculator.