Tire Size Calculator
Convert Tire Sizes Easily with Our Free Calculator
TireSizeConversionCalculator.com is a free, web-based tool that helps you instantly convert metric tire sizes (like 225/65R17) into their inch equivalents, including key specifications like overall diameter, section width, sidewall height, and circumference. This is especially helpful for tire comparisons, wheel upgrades, suspension planning, or ensuring compliance with vehicle fitment rules.
Understanding tire size conversions can be confusing — especially when switching between metric and imperial systems. Most tire size labels show numbers in millimeters, but your vehicle’s clearance, wheel well space, or speedometer calibration may depend on actual inches. That’s where this tool comes in.
Whether You're:
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1. 🔧 A mechanic confirming fitment for a lift kit or larger rims
2. 🚙 An off-road enthusiast evaluating all-terrain tire options
3. A car owner replacing OEM tires and wanting to compare alternatives
4. 🧮 A DIY builder customizing classic or performance vehicles
✨ Key Benefits:
- No login or app required — it works instantly in any browser
- Supports most standard passenger tire sizes
- Displays both inch-based and metric-based results for clarity
- Mobile-friendly layout for use at the shop or on the go
- Fast and free with no ads interfering with your calculations
We created this tool to eliminate the guesswork and save you time when upgrading your wheels or comparing tire options. By inputting a single metric size, you’ll receive a breakdown that helps ensure safety, compatibility, and performance for your vehicle.
Convert metric tire sizes (e.g., 225/65R17) to inches.
Frequently Asked Questions
What does 225/65R17 mean?
225 is the tire width in mm, 65 is the aspect ratio (height % of width), and 17 is the wheel diameter in inches.
How is overall diameter calculated?
It's the height of two sidewalls plus the rim diameter.
Will changing my tire size affect speedometer accuracy?
Yes, even small differences in diameter can change your speed reading.
Can I use this tire size on my car?
Always check with your vehicle manual or a tire professional for compatibility.
What is the difference between tire width and tread width?
Tire width is measured from sidewall to sidewall. Tread width is the part of the tire that contacts the road—usually narrower.
What is the aspect ratio in tire size?
The aspect ratio is the sidewall height expressed as a percentage of the tire’s width. For example, 65 means the sidewall is 65% as tall as the width.
What does the “R” in 225/65R17 mean?
“R” stands for Radial, indicating the internal construction of the tire. Most modern tires are radial for better stability and flexibility.
Is it safe to change my tire size?
Slight changes (within 3%) are generally safe. Large changes can affect handling, brakes, and speedometer accuracy. Always consult a tire expert.
What happens if my tires are too tall or too wide?
Oversized tires can rub on fenders or suspension parts and may throw off handling and fuel efficiency. Ensure they fit your vehicle’s clearance.
Do larger tires improve performance?
Sometimes, larger tires can improve grip or aesthetics, but they often reduce fuel efficiency and can negatively impact ride comfort.
Can I use this calculator for off-road or winter tires?
Yes, but remember off-road and winter tires may have deeper tread patterns that slightly affect true diameter. Use it as a close estimate.
How do I find the recommended tire size for my car?
Look on the driver’s door frame sticker, inside the glove box, or in your owner’s manual. That’s the manufacturer's recommended size.