Plus Sizing Tire Calculator
Find equivalent tire sizes when upgrading wheel diameter while keeping overall diameter and speedometer error in check.
REAL-WORLD EXAMPLE
Your stock size is 225/45R17 with an overall diameter of about 24.97". A common Plus-1 option is 245/40R18, which increases wheel diameter by 1" and lowers the aspect ratio. The new overall diameter is roughly 25.7" — about +3%, right at the upper edge of the widely used ±3% guideline. Our calculator helps you spot Plus-0, Plus-1, and Plus-2 sizes that stay as close as possible to your original diameter while improving stance and handling.
Plus Sizing Options Calculator
Enter 18 for Plus-1, 19 for Plus-2, etc.
Popular Plus Sizing Options
| Stock Size | Typical Plus-1 Size | Dia. Change (approx.) | Main Benefit |
|---|---|---|---|
| 205/55R16 | 225/45R17 | ≈ +0.5–1.5% | Sharper handling, sportier look |
| 225/45R17 | 245/40R18 | ≈ +3% | Aggressive upgrade near 3% limit |
| 245/40R18 | 265/35R19 | ≈ 0–2% | Premium appearance, larger brakes |
| 265/70R17 | 285/65R18 | ≈ 0–3% | Truck/SUV plus-sizing with lift-friendly stance |
Dia. change values above are approximate and based on nominal sizes. Use the calculator with your exact sizes to see precise diameter and speedometer differences for your vehicle.
How to Use This Calculator
- Enter your current (stock) tire size from the sidewall.
- Choose how many inches you want to increase wheel diameter (Plus-0, Plus-1, Plus-2, etc.).
- Click 'Find Plus Size Options'.
- Review the suggested equivalent sizes, including overall diameter change, speedometer error, and sidewall height.
- Use the ±3% diameter guideline as a quick check, then verify fitment and load rating for your specific vehicle before buying.
Plus Sizing Formula & Diameter Guidelines
About Plus Sizing & Safe Tire Upgrades
How Plus-0, Plus-1 and Plus-2 Fitments Work
Plus-0 keeps the same wheel diameter and mostly changes width and aspect ratio. Plus-1 increases wheel diameter by 1" with a slightly wider, lower profile tire, and Plus-2 increases wheel diameter by 2". In each case you adjust tire width and aspect ratio so that overall diameter stays close to stock, preserving the way your speedometer, ABS, and drivetrain were calibrated from the factory.
Balancing Handling, Comfort and Durability
Lower-profile plus-size tires can make the car feel more responsive, but they also give the sidewall less room to absorb potholes and rough roads. That can mean a firmer ride, more road noise, and a higher chance of wheel or tire damage on impacts. Heavier wheel and tire packages may also slightly reduce fuel economy and add wear to suspension components. Using this calculator helps you target sizes that improve performance and appearance without straying too far from your vehicle's original design envelope.
Using the Calculator with Other Fitment Tools
Plus sizing is only one part of a safe wheel and tire setup. Before buying, you should also confirm that your chosen tire width is appropriate for your rim width, that wheel offset keeps the tires clear of suspension and bodywork, and that load index and speed rating meet or exceed OE requirements. Pair this tool with rim width, offset, and tire size calculators, then test-fit combinations on the vehicle whenever possible before committing.