Tire Size Calculator
Calculate tire dimensions, compare different tire sizes, and analyze performance impact. Get accurate measurements for sidewall height, diameter, circumference, and speedometer accuracy for optimal vehicle performance.
Enter Tire Specifications
Main Tire Size
Example: 225/60R16
Width/Aspect Ratio R Wheel Diameter format
Enter tire specifications and click 'Calculate Dimensions' to see results
What is a Tire Size Calculator?
A Tire Size Calculator is a tool that calculates tire dimensions and compares different tire sizes to help you understand their impact on vehicle performance. It provides accurate measurements for sidewall height, total diameter, circumference, and analyzes how tire size changes affect speedometer accuracy and vehicle dynamics.
Key Features
- •Calculate tire dimensions from size specifications
- •Compare two different tire sizes side by side
- •Analyze speedometer accuracy impact
- •Calculate revolutions per kilometer/mile
- •Performance impact analysis
- •Support for metric and imperial units
- •Multiple tire format support (P-metric, LT, flotation)
- •Export results to CSV for record keeping
Benefits
- ✓Make informed tire upgrade decisions
- ✓Understand performance trade-offs
- ✓Ensure proper fitment and clearance
- ✓Maintain accurate speedometer readings
- ✓Optimize vehicle handling and comfort
- ✓Compare tire options before purchasing
- ✓Verify manufacturer specifications
Step-by-Step Instructions
- 1
Select Unit System
Choose between metric (millimeters/kilometers) or imperial (inches/miles) units based on your preference.
- 2
Choose Tire Format
Select the appropriate tire format: P-metric (225/60R16), Imperial (31x10.5R15), or Flotation (33x12.50R15LT).
- 3
Enter Primary Tire Size
Input the width, aspect ratio, and rim diameter for your primary tire size.
- 4
Add Comparison Tire (Optional)
Enable comparison mode and enter a second tire size to compare dimensions and performance impact.
- 5
Calculate and Analyze
Click 'Calculate Dimensions' to get detailed measurements, comparisons, and performance analysis.
Tips for Accurate Results
- 💡Double-check tire size markings on your current tires
- 💡Consider load index and speed rating requirements
- 💡Verify wheel well clearance for larger tires
- 💡Check manufacturer recommendations for your vehicle
- 💡Consider the impact on fuel economy and ride quality
Applications of Tire Size Calculation
Tire size calculation is essential in various automotive scenarios:
Tire Upgrades
Planning tire upgrades for improved performance, appearance, or capability.
- •Plus sizing for better handling
- •Off-road tire selection
- •Performance tire upgrades
- •Winter tire sizing
Vehicle Modification
Ensuring proper fitment when modifying suspension or wheels.
- •Lowering or lifting vehicle
- •Wheel diameter changes
- •Fender clearance verification
- •Speedometer calibration
Fleet Management
Standardizing tire sizes across vehicle fleets for efficiency.
- •Commercial fleet optimization
- •Maintenance cost reduction
- •Inventory management
- •Performance standardization
Tire Dimension Calculation Formulas
The tire size calculator uses these fundamental formulas:
Basic Calculation Formulas
Sidewall Height = (Tire Width × Aspect Ratio) / 100
Total Diameter = (2 × Sidewall Height) + Rim Diameter
Circumference = π × Total Diameter
These formulas convert tire size markings into actual physical dimensions.
Formula Variables
- •Tire Width: The width of the tire tread in millimeters or inches
- •Aspect Ratio: The ratio of sidewall height to tire width (percentage)
- •Rim Diameter: The diameter of the wheel rim in inches
- •π (Pi): Mathematical constant approximately equal to 3.14159
Factors Affecting Tire Performance
Several factors influence how tire size changes affect vehicle performance:
Handling and Performance
- •Lower profile tires improve handling but reduce ride comfort
- •Wider tires provide better grip but increase rolling resistance
- •Larger diameter wheels improve braking performance
- •Tire pressure affects contact patch and handling
Fuel Economy and Efficiency
- •Larger/heavier tires reduce fuel economy
- •Rolling resistance increases with tire size
- •Aerodynamic drag changes with tire width
- •Proper inflation maintains optimal efficiency
Ride Quality and Comfort
- •Higher sidewall provides better ride comfort
- •Lower profile tires transmit more road noise
- •Tire construction affects vibration damping
- •Load capacity must match vehicle requirements
Best Practices for Tire Sizing
Follow these guidelines when selecting or changing tire sizes:
Stay Within Manufacturer Guidelines
Always check your vehicle manufacturer's approved tire size ranges to ensure safety and warranty compliance.
Maintain Overall Diameter
Keep the total tire diameter within 3% of the original to minimize speedometer error and maintain proper vehicle dynamics.
Consider Load Rating
Ensure the new tire's load index meets or exceeds the original tire's rating to safely support your vehicle's weight.
Check Clearance
Verify adequate clearance in wheel wells, especially when turning or under suspension compression.
Match Tire Sizes
Use identical tire sizes on the same axle and consider the impact of different sizes on all-wheel-drive systems.
What does the tire size marking mean?
A tire size like 225/60R16 means: 225mm width, 60% aspect ratio (sidewall height is 60% of width), R indicates radial construction, and 16 is the rim diameter in inches.
How much can I change tire size safely?
Generally, keep the overall diameter within 3% of the original size. Larger changes can affect speedometer accuracy, handling, and may cause clearance issues.
Will larger tires affect my speedometer?
Yes, larger overall diameter tires will make your speedometer read slower than actual speed, while smaller tires will make it read faster. The calculator shows this error percentage.
What's the difference between plus sizing?
Plus sizing increases wheel diameter while decreasing sidewall height to maintain similar overall diameter. Plus 1 adds 1 inch to wheel diameter, Plus 2 adds 2 inches, etc.
How do I read imperial tire sizes?
Imperial sizes like 31x10.5R15 mean: 31 inches overall diameter, 10.5 inches width, R for radial, and 15 inches rim diameter. This format is common for off-road tires.