225/45R18 dimensions
| Measure | Inches | Millimetres |
|---|---|---|
| Overall height | 25.97 in | 660 mm |
| Section width | 8.86 in | 225 mm |
| Sidewall height | 3.99 in | 101.2 mm |
| Wheel diameter | 18 in | 457 mm |
| Circumference | 81.6 in | 2,073 mm |
| Revolutions per mile | 776.5 |
The math
| Step | Math | Result |
|---|---|---|
| Sidewall | 225 × 45% = 101.2 mm ÷ 25.4 | 3.99 in |
| Overall height | 18 + 2 × 3.99 | 25.97 in |
| Width | 225 mm ÷ 25.4 | 8.86 in |
| Circumference | π × 25.97 | 81.6 in |
| Revs per mile | 63,360 ÷ 81.6 | 776.5 |
With a 4.0 in sidewall this is a medium sidewall: a balance of cushion and response. Real tires vary by brand and model, and the loaded radius under the vehicle is a bit smaller than this unloaded figure.
One step either way on a 18 in wheel
Each row changes one thing and shows the height change against 225/45R18, plus what 60 mph on the speedometer would really be if you swapped to that size.
| Change | Size | Height | Height change | 60 mph shows as | Verdict |
|---|---|---|---|---|---|
| Wider | 235/45R18 (compare) | 26.3 in | +1.4% | 60.8 mph | Close match |
| Narrower | 215/45R18 (compare) | 25.6 in | -1.4% | 59.2 mph | Close match |
| Taller sidewall | 225/50R18 (compare) | 26.9 in | +3.4% | 62.0 mph | Check clearance |
| Shorter sidewall | 225/40R18 (compare) | 25.1 in | -3.4% | 58.0 mph | Check clearance |
| Wider, shorter sidewall | 235/40R18 (compare) | 25.4 in | -2.2% | 58.7 mph | Close match |
| Narrower, taller sidewall | 215/50R18 (compare) | 26.5 in | +1.9% | 61.1 mph | Close match |
Calculated sizes within ±3% on other wheels
Plus and minus sizes that keep the overall height within about 3% (a rule of thumb from Discount Tire and 1010tires), widths within 30 mm. Calculated, not a list of tires on sale: check that a tire exists in that size.
17 in wheels (one wheel size smaller)
| Size | Height | Height change | Width change |
|---|---|---|---|
| 255/45R17 (compare) | 26.0 in | +0.2% | +30 mm |
| 205/55R17 (compare) | 25.9 in | -0.4% | -20 mm |
| 225/50R17 (compare) | 25.9 in | -0.4% | +0 mm |
| 195/60R17 (compare) | 26.2 in | +0.9% | -30 mm |
19 in wheels (one wheel size larger)
| Size | Height | Height change | Width change |
|---|---|---|---|
| 255/35R19 (compare) | 26.0 in | +0.2% | +30 mm |
| 195/45R19 (compare) | 25.9 in | -0.2% | -30 mm |
| 225/40R19 (compare) | 26.1 in | +0.4% | +0 mm |
| 215/40R19 (compare) | 25.8 in | -0.8% | -10 mm |
20 in wheels (two wheel sizes larger)
| Size | Height | Height change | Width change |
|---|---|---|---|
| 215/35R20 (compare) | 25.9 in | -0.2% | -10 mm |
| 255/30R20 (compare) | 26.0 in | +0.2% | +30 mm |
| 195/40R20 (compare) | 26.1 in | +0.7% | -30 mm |
| 245/30R20 (compare) | 25.8 in | -0.7% | +20 mm |
Try it with your numbers
Compare 225/45R18 with another size · Convert to metric or find a 33 in size · Sizes that fit my wheel
Calculated from the size alone. Real tires vary a little by brand and model, and the loaded radius is a bit smaller. Confirm the wheel width range, clearance, load index and speed rating for your vehicle. See how to read a tire size, the load index chart and the speed rating chart.
Browse: all sizes in inches · 225/40R18 · 225/50R18.