Wheels & Tires Calculators
3 free calculators for Wheels & Tires.
Plus-size tire calculator
Moving to bigger wheels? This lists the tire sizes that keep your overall diameter close to the original, so your speedometer and gearing stay right.
Tire size converter
Turn a metric size like 265/70R17 into inches, convert an inch size like 33×12.50R15 to metric, and compare two sizes side by side.
Wheel offset and backspacing calculator
Compare a new wheel to your current one before you buy: how much closer it sits to the suspension and how much farther it pokes out toward the fender.
A wheel and tire change affects more than looks. The overall tire diameter changes the speedometer and gearing, the width and offset decide whether the wheel clears the suspension and body, and the load rating decides whether it is safe to carry the vehicle.
Which tool answers which question
- Plus-size tire calculator: Moving to bigger wheels? This lists the tire sizes that keep your overall diameter close to the original, so your speedometer and gearing stay right.
- Tire size converter: Turn a metric size like 265/70R17 into inches, convert an inch size like 33×12.50R15 to metric, and compare two sizes side by side.
- Wheel offset and backspacing calculator: Compare a new wheel to your current one before you buy: how much closer it sits to the suspension and how much farther it pokes out toward the fender.
Plus sizing and overall diameter
Plus sizing means fitting a larger wheel with a lower-profile tire so the overall diameter stays close to the original. A common guideline is to stay within about 3 percent of the original diameter, which keeps the speedometer and gearing close. The tire size tools compare the dimensions of two sizes so you can see the difference.
Offset and backspacing
Offset is the distance from the wheel's mounting face to its centerline, and backspacing is the distance from the mounting face to the back edge of the wheel. Both decide where the wheel sits relative to the suspension and fender. Check the clearance at full steering lock and full suspension travel, and confirm the load index and speed rating with a tire professional.
Common mistakes
- Checking diameter only. Width and offset decide clearance.
- Ignoring the load rating. The tire must carry the vehicle's weight.
- Skipping the lock-to-lock check. A tire that clears straight ahead may rub when turning.
Guides for this section
Want the background behind these tools? These guides explain the thinking and the numbers in more depth.