Tire Size Calculator
Calculate tire dimensions, diameter, and revolutions per mile
Enter Tire Specifications
Tire Specifications
About This Calculator
The Tire Size Calculator helps you understand tire dimensions and specifications. Enter the tire width, aspect ratio, and rim diameter to calculate the tire's total diameter, circumference, and revolutions per mile.
This tool is essential for vehicle owners who need to understand tire specifications, calculate speedometer accuracy, or determine if a tire size will fit their vehicle. The calculator uses standard tire sizing notation (e.g., 225/50R17).
Formula & Calculation Method
The tire size calculation uses the following formulas:
- Sidewall Height (mm): Width × (Aspect Ratio / 100)
- Total Diameter (inches): (Sidewall Height × 2 / 25.4) + Rim Diameter
- Circumference (inches): Diameter × π
- Revolutions per Mile: 63,360 / Circumference
Where:
- Width is in millimeters (mm)
- Aspect Ratio is the sidewall height as a percentage of width
- Rim Diameter is in inches
- 25.4 is the conversion factor from mm to inches
How to Use This Calculator
Frequently Asked Questions
What is tire aspect ratio?
Aspect ratio is the height of the tire sidewall expressed as a percentage of the tire width. For example, a 225/50 tire has a sidewall height that is 50% of 225mm, which equals 112.5mm.
How do I read tire size?
Tire size is typically written as Width/AspectRatioRimDiameter (e.g., 225/50R17). The width is in millimeters, aspect ratio is a percentage, and rim diameter is in inches.
Why is tire diameter important?
Tire diameter affects speedometer accuracy, vehicle clearance, and overall vehicle performance. Changing tire size can impact fuel economy and handling characteristics.
Can I use different tire sizes on my vehicle?
You should consult your vehicle manufacturer's specifications. Different tire sizes can affect speedometer accuracy, ABS systems, and vehicle handling. Always ensure new tires meet your vehicle's load and speed rating requirements.
Expert Reviewed
This calculator was reviewed by NumCalculators Editorial Team, Multi-disciplinary Expert Team