RimRatio

Plus size tire calculator

Moving to 18- or 20-inch wheels — or down a size for winter? Enter your current tire and the new wheel diameter to list every standard metric size that keeps the overall diameter within tolerance.

13 theoretical 18-inch sizes (1 in larger wheel) have an overall diameter within ±3% of 225/65R17 (28.52 in), sorted by closest diameter. Not every combination is manufactured.

SizeDiameterWidthvs original
205/65R1828.49 in8.07 in−0.08%
265/50R1828.43 in10.43 in−0.29%
245/55R1828.61 in9.65 in+0.33%
225/60R1828.63 in8.86 in+0.40%
235/55R1828.18 in9.25 in−1.19%
215/60R1828.16 in8.46 in−1.26%
255/50R1828.04 in10.04 in−1.67%
215/65R1829.00 in8.46 in+1.71%
255/55R1829.04 in10.04 in+1.85%
235/60R1829.10 in9.25 in+2.06%
225/55R1827.74 in8.86 in−2.71%
205/70R1829.30 in8.07 in+2.75%
205/60R1827.69 in8.07 in−2.91%

Geometry only: this does not confirm that a size fits, is approved for or is safe on a particular vehicle. Wheel width and offset, suspension, clearances, load index, speed rating, the vehicle maker's specification and local regulations all apply — check with your owner's manual and a qualified tire professional.

How to choose from the list

  1. Start with the smallest diameter difference (top of the table).
  2. Note the width: it changes clearance and the range of rim widths the tire maker approves for that size.
  3. Check the load index and speed rating of any actual tire against your vehicle placard and owner's manual.
  4. Confirm the size is actually manufactured — the calculator lists theoretical combinations.
  5. Have fitment confirmed by a qualified tire professional; diameter matching alone does not establish it.

Frequently asked questions

What is plus sizing?

Fitting a larger wheel with a lower-profile tire so the overall diameter stays about the same. "Plus one" goes up one inch: 205/55R16 (24.88 in) → 225/45R17 (24.97 in) → 225/40R18 (25.09 in) for "plus two".

Is minus sizing a thing?

Yes — a smaller wheel with a taller-sidewall tire that keeps a similar overall diameter. Choose a smaller rim in the calculator; a smaller wheel must still clear the brakes and suit the vehicle.

Will a plus-size tire carry the same load?

Not necessarily — load capacity depends on the specific tire, not on its diameter. Some lower-profile tires are made in "XL" (extra load) versions. Check the load index and speed rating your vehicle requires on its placard and in the owner's manual.

Does a bigger wheel fit my brakes and suspension?

The calculator cannot tell you. Brake clearance depends on the wheel's design, diameter and offset as well as the calipers, and any wheel must also match the bolt pattern, center bore, width and load rating your vehicle requires. The calculator only compares tire diameters.

Related tools