Plus-Size and Winter Downsize Calculator
Find compatible alternate tire sizes when changing your rim diameter for performance upgrades or winter driving.
Quick Answer
If your factory vehicle comes with 225/50R17 tires, a proper "+1" plus-size for larger 18-inch wheels is a 225/45R18, keeping the overall diameter almost identical at 26.0 inches. For a "-1" winter downsize, a 215/60R16 offers a narrower footprint for better snow traction while perfectly matching the factory height.
Enter Tire Specifications
① Original Tire
→ 265/70R17
② Compare Tire
→ 285/70R17
Enter tire specs above and click Calculate to compare
Supports P-metric (225/65R17) and Imperial/flotation (31x10.5R15) formats
Common Plus and Minus Sizing (Base: 225/65R17 — 28.5" Diameter)
| Fitment Type | Tire Size | Rim | Overall Diameter | Best Used For |
|---|---|---|---|---|
| Minus-2 | 225/75R15 | 15 inch | 28.3" | Heavy Winter / Off-Road |
| Minus-1 | 225/70R16 | 16 inch | 28.4" | Standard Winter Set |
| Factory (OEM) | 225/65R17 | 17 inch | 28.5" | All-Season Daily Driving |
| Plus-1 | 235/55R18 | 18 inch | 28.2" | Sport Handling Upgrade |
| Plus-2 | 245/45R19 | 19 inch | 28.7" | High Performance / Aesthetics |
| Plus-3 | 245/40R20 | 20 inch | 28.7" | Maximum Street Styling |
Formula
Target Aspect Ratio = ((Target Diameter − New Rim Size) × 25.4) / (2 × Target Width) × 100
- Target Diameter = factory tire overall height in inches
- New Rim Size = desired wheel diameter in inches
- Target Width = desired tire width in mm
- Example: Moving to 18" rim, keeping 26" diameter, 225mm width: ((26 − 18) × 25.4) / (2 × 225) × 100 = 45.1 → round to 45