255/45R18
A 255/45R18 tire is 27.04 inches tall and 10.0 inches wide, with a 4.52-inch sidewall, mounted on a 18-inch wheel.
Overall diameter
27.04″
687 mm
Sidewall height
4.52″
114.8 mm
Tread width
255 mm
10.0″
Circumference
84.93″
7.1 ft
Revs per mile
746
464 per km
Wheel diameter
18″
aspect ratio 45%
Cross-section
- Overall diameter
- 27.04″
- Sidewall (each side)
- 4.52″
- Wheel
- 18″
255/45R18 in inches and millimeters
Every dimension of a 255/45R18, converted both ways. Calculated from the size code, accurate to about 1%.
| Measurement | Inches | Millimeters |
|---|---|---|
| Overall diameter (height) | 27.04″ | 687 mm |
| Tread width | 10.0″ | 255 mm |
| Sidewall height | 4.52″ | 114.8 mm |
| Wheel diameter | 18″ | 457 mm |
| Circumference | 84.93″ | 2157 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.
255/45R18 compared with other sizes
All 35 practical swaps involving 255/45R18 — diameter change, speedometer impact and a fit verdict for each.
255/45R18 → 215/65R16
215/65R16
Diameter +0.1% · This fits
255/45R18 → 225/60R16
225/60R16
Diameter +1.5% · This fits
255/45R18 → 235/60R16
235/60R16
Diameter −0.2% · This fits
255/45R18 → 235/55R17
235/55R17
Diameter −0.5% · This fits
255/45R18 → 225/45R18
225/45R18
Diameter +4.1% · Borderline. Check clearance first
255/45R18 → 235/45R18
235/45R18
Diameter +2.7% · This fits
255/45R18 → 235/50R18
235/50R18
Diameter −0.8% · This fits
255/45R18 → 245/40R18
245/40R18
Diameter +5.1% · Too big a jump
255/45R18 → 245/45R18
245/45R18
Diameter +1.3% · This fits
255/45R18 → 245/40R19
245/40R19
Diameter +1.2% · This fits
255/45R18 → 255/40R19
255/40R19
Diameter +0.0% · This fits
255/45R18 → 245/35R20
245/35R20
Diameter +1.1% · This fits
255/45R18 → 255/35R20
255/35R20
Diameter +0.0% · This fits
255/45R18 → 295/35R20
295/35R20
Diameter −3.9% · Borderline. Check clearance first
255/45R18 → 225/65R16
225/65R16
Diameter −1.7% · This fits
255/45R18 → 215/60R17
215/60R17
Diameter −0.4% · This fits
255/45R18 → 235/55R18
235/55R18
Diameter −4.1% · Borderline. Check clearance first
255/45R18 → 255/40R18
255/40R18
Diameter +3.9% · Borderline. Check clearance first
235/50R18 → 255/45R18
235/50R18
Diameter +0.8% · This fits
245/45R18 → 255/45R18
245/45R18
Diameter −1.3% · This fits
255/40R18 → 255/45R18
255/40R18
Diameter −3.7% · Borderline. Check clearance first
235/45R18 → 255/45R18
235/45R18
Diameter −2.6% · This fits
255/40R19 → 255/45R18
255/40R19
Diameter −0.0% · This fits
255/35R20 → 255/45R18
255/35R20
Diameter −0.0% · This fits
225/45R18 → 255/45R18
225/45R18
Diameter −3.9% · Borderline. Check clearance first
235/55R18 → 255/45R18
235/55R18
Diameter +4.2% · Borderline. Check clearance first
245/40R18 → 255/45R18
245/40R18
Diameter −4.9% · Borderline. Check clearance first
215/65R16 → 255/45R18
215/65R16
Diameter −0.1% · This fits
235/60R16 → 255/45R18
235/60R16
Diameter +0.2% · This fits
215/60R17 → 255/45R18
215/60R17
Diameter +0.5% · This fits
235/55R17 → 255/45R18
235/55R17
Diameter +0.5% · This fits
265/35R20 → 255/45R18
265/35R20
Diameter +1.0% · This fits
255/45R18 → 235/45R19
235/45R19
Diameter −1.1% · This fits
255/45R18 → 265/35R20
265/35R20
Diameter −1.0% · This fits
255/45R18 → 275/35R20
275/35R20
Diameter −2.0% · This fits
Common questions
- What is 255/45R18 in inches?
- A 255/45R18 tire is 27.04 inches tall and 10.0 inches wide, with a 4.52-inch sidewall, mounted on a 18-inch wheel. In metric that is 687 mm tall and 255 mm wide. The circumference is 84.93 inches.
- How tall is a 255/45R18 tire?
- 27.04 inches, or 687 mm. That is the overall diameter, wheel included. It turns about 746 times per mile, which is what your speedometer counts.
- What do the numbers in 255/45R18 mean?
- 255 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 255 × 45% = 114.8 mm tall.