225/45R18
A 225/45R18 tire is 25.97 inches tall and 8.9 inches wide, with a 3.99-inch sidewall, mounted on a 18-inch wheel.
Common fitments: Civic Sport, Mazda3
Overall diameter
25.97″
660 mm
Sidewall height
3.99″
101.3 mm
Tread width
225 mm
8.9″
Circumference
81.59″
6.8 ft
Revs per mile
777
483 per km
Wheel diameter
18″
aspect ratio 45%
Cross-section
- Overall diameter
- 25.97″
- Sidewall (each side)
- 3.99″
- Wheel
- 18″
225/45R18 in inches and millimeters
Every dimension of a 225/45R18, converted both ways. Calculated from the size code, accurate to about 1%.
| Measurement | Inches | Millimeters |
|---|---|---|
| Overall diameter (height) | 25.97″ | 660 mm |
| Tread width | 8.9″ | 225 mm |
| Sidewall height | 3.99″ | 101.3 mm |
| Wheel diameter | 18″ | 457 mm |
| Circumference | 81.59″ | 2073 mm |
Nominal dimensions from the size code. A real tire varies by a few millimeters between manufacturers, and a loaded tire sits slightly shorter than its free diameter.
225/45R18 compared with other sizes
All 31 practical swaps involving 225/45R18 — diameter change, speedometer impact and a fit verdict for each.
225/45R18 → 205/60R16
205/60R16
Diameter +1.1% · This fits
225/45R18 → 215/60R16
215/60R16
Diameter −0.7% · This fits
225/45R18 → 225/60R16
225/60R16
Diameter −2.5% · This fits
225/45R18 → 225/50R17
225/50R17
Diameter +0.4% · This fits
225/45R18 → 245/45R17
245/45R17
Diameter +1.1% · This fits
225/45R18 → 225/40R18
225/40R18
Diameter +3.5% · Borderline. Check clearance first
255/40R18 → 225/45R18
255/40R18
Diameter +0.2% · This fits
245/40R18 → 225/45R18
245/40R18
Diameter −1.0% · This fits
235/45R18 → 225/45R18
235/45R18
Diameter +1.4% · This fits
225/40R18 → 225/45R18
225/40R18
Diameter −3.4% · Borderline. Check clearance first
235/40R18 → 225/45R18
235/40R18
Diameter −2.2% · This fits
245/45R18 → 225/45R18
245/45R18
Diameter +2.7% · This fits
255/45R18 → 225/45R18
255/45R18
Diameter +4.1% · Borderline. Check clearance first
225/50R17 → 225/45R18
225/50R17
Diameter −0.4% · This fits
235/50R18 → 225/45R18
235/50R18
Diameter +4.9% · Borderline. Check clearance first
255/35R19 → 225/45R18
255/35R19
Diameter +0.2% · This fits
215/60R16 → 225/45R18
215/60R16
Diameter +0.7% · This fits
245/35R19 → 225/45R18
245/35R19
Diameter −0.8% · This fits
205/60R16 → 225/45R18
205/60R16
Diameter −1.1% · This fits
245/45R17 → 225/45R18
245/45R17
Diameter −1.1% · This fits
225/45R18 → 235/40R18
235/40R18
Diameter +2.2% · This fits
225/45R18 → 235/45R18
235/45R18
Diameter −1.3% · This fits
225/45R18 → 235/50R18
235/50R18
Diameter −4.7% · Borderline. Check clearance first
225/45R18 → 245/40R18
245/40R18
Diameter +1.0% · This fits
225/45R18 → 245/45R18
245/45R18
Diameter −2.7% · This fits
225/45R18 → 235/40R19
235/40R19
Diameter −1.6% · This fits
225/45R18 → 245/35R19
245/35R19
Diameter +0.9% · This fits
225/45R18 → 255/35R19
255/35R19
Diameter −0.2% · This fits
225/45R18 → 205/65R16
205/65R16
Diameter −2.0% · This fits
225/45R18 → 255/40R18
255/40R18
Diameter −0.2% · This fits
225/45R18 → 255/45R18
255/45R18
Diameter −3.9% · Borderline. Check clearance first
Common questions
- What is 225/45R18 in inches?
- A 225/45R18 tire is 25.97 inches tall and 8.9 inches wide, with a 3.99-inch sidewall, mounted on a 18-inch wheel. In metric that is 660 mm tall and 225 mm wide. The circumference is 81.59 inches.
- How tall is a 225/45R18 tire?
- 25.97 inches, or 660 mm. That is the overall diameter, wheel included. It turns about 777 times per mile, which is what your speedometer counts.
- What do the numbers in 225/45R18 mean?
- 225 is the tread width in millimeters, 45 is the aspect ratio — the sidewall height as a percentage of the tread width — and 18 is the wheel diameter in inches. So the sidewall is 225 × 45% = 101.3 mm tall.