Tire Size Calculator

Tire Size Calculator

Compare tire sizes, calculate speedometer differences, and analyze tire specifications. Perfect for upgrading wheels or understanding tire dimensions.

Current Tire

Range: 135-345 mm

Range: 30-85%

Range: 13-24 inches

New Tire

Range: 135-345 mm

Range: 30-85%

Range: 13-24 inches

Speedometer Analysis

Range: 1-200 mph

About Tire Size Calculator

Our comprehensive tire size calculator helps you compare different tire dimensions and understand their impact on vehicle performance. Whether you're upgrading wheels, changing tire sizes, or analyzing tire specifications, this tool provides accurate calculations for circumference, speedometer accuracy, and performance characteristics.

What It Calculates

  • Tire Dimensions: Width, aspect ratio, and diameter measurements
  • Circumference: Distance around the tire's outer edge
  • Revolutions per Mile: How many times the tire rotates per mile
  • Sidewall Height: Distance from rim to tread surface
  • Speedometer Accuracy: Impact on speed reading accuracy
  • Performance Comparison: Side-by-side analysis of different sizes

Understanding Tire Size Notation

Metric System (P-Metric)
  • P215/65R15
  • P = Passenger vehicle
  • 215 = Width in millimeters
  • 65 = Aspect ratio percentage
  • R = Radial construction
  • 15 = Rim diameter in inches
Imperial System
  • 31x10.50R15
  • 31 = Overall diameter in inches
  • 10.50 = Width in inches
  • R = Radial construction
  • 15 = Rim diameter in inches
  • Common for off-road tires

Understanding Your Results

Circumference

Distance around tire

Revolutions

Rotations per mile

Speedometer

Accuracy impact

How to Use

Enter your current tire size and the new tire size you want to compare. The calculator will show the differences in dimensions, performance characteristics, and how the change affects your speedometer accuracy.

Tire Size Impact on Performance

  • Larger Tires: Better ground clearance, improved off-road capability
  • Smaller Tires: Better fuel economy, improved acceleration
  • Wider Tires: Better traction, improved cornering stability
  • Narrower Tires: Better fuel efficiency, improved snow performance
  • Lower Aspect Ratio: Better handling, stiffer ride
  • Higher Aspect Ratio: Smoother ride, better comfort

Speedometer Accuracy

Why Speedometer Accuracy Matters: Changing tire sizes affects how your speedometer reads. Larger tires make your speedometer read slower than actual speed, while smaller tires make it read faster.

Larger Tires:

  • Speedometer reads slower
  • Odometer reads fewer miles
  • Risk of speeding tickets

Smaller Tires:

  • Speedometer reads faster
  • Odometer reads more miles
  • May affect warranty

Common Tire Size Changes

  • Plus Sizing: Increasing rim diameter while maintaining overall diameter
  • Plus Zero: Changing width while maintaining overall diameter
  • Plus One/Two: Increasing rim diameter by 1-2 inches
  • Off-Road Upgrades: Larger tires for improved ground clearance
  • Performance Upgrades: Lower profile tires for better handling
  • Winter Tires: Smaller diameter for better snow performance

Safety Considerations

  • Clearance Issues: Ensure tires don't rub against vehicle components
  • Load Capacity: Verify new tires can handle vehicle weight
  • Speed Rating: Ensure tires meet or exceed vehicle requirements
  • Legal Compliance: Check local regulations on tire modifications
  • Professional Installation: Have changes made by qualified technicians
Pro Tip

When changing tire sizes, aim to keep the overall diameter within 3% of the original size to maintain proper speedometer accuracy and avoid potential issues with vehicle systems like ABS and traction control. Always consult your vehicle's manual and a qualified tire professional for guidance.