225/45R18
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 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% · Good fit
225/45R18 → 215/60R16
215/60R16
Diameter −0.7% · Good fit
225/45R18 → 225/60R16
225/60R16
Diameter −2.5% · Good fit
225/45R18 → 225/50R17
225/50R17
Diameter +0.4% · Good fit
225/45R18 → 245/45R17
245/45R17
Diameter +1.1% · Good fit
225/45R18 → 225/40R18
225/40R18
Diameter +3.5% · Marginal fit — proceed with care
255/40R18 → 225/45R18
255/40R18
Diameter +0.2% · Good fit
245/40R18 → 225/45R18
245/40R18
Diameter −1.0% · Good fit
235/45R18 → 225/45R18
235/45R18
Diameter +1.4% · Good fit
225/40R18 → 225/45R18
225/40R18
Diameter −3.4% · Marginal fit — proceed with care
235/40R18 → 225/45R18
235/40R18
Diameter −2.2% · Good fit
245/45R18 → 225/45R18
245/45R18
Diameter +2.7% · Good fit
255/45R18 → 225/45R18
255/45R18
Diameter +4.1% · Marginal fit — proceed with care
225/50R17 → 225/45R18
225/50R17
Diameter −0.4% · Good fit
235/50R18 → 225/45R18
235/50R18
Diameter +4.9% · Marginal fit — proceed with care
255/35R19 → 225/45R18
255/35R19
Diameter +0.2% · Good fit
215/60R16 → 225/45R18
215/60R16
Diameter +0.7% · Good fit
245/35R19 → 225/45R18
245/35R19
Diameter −0.8% · Good fit
205/60R16 → 225/45R18
205/60R16
Diameter −1.1% · Good fit
245/45R17 → 225/45R18
245/45R17
Diameter −1.1% · Good fit
225/45R18 → 235/40R18
235/40R18
Diameter +2.2% · Good fit
225/45R18 → 235/45R18
235/45R18
Diameter −1.3% · Good fit
225/45R18 → 235/50R18
235/50R18
Diameter −4.7% · Marginal fit — proceed with care
225/45R18 → 245/40R18
245/40R18
Diameter +1.0% · Good fit
225/45R18 → 245/45R18
245/45R18
Diameter −2.7% · Good fit
225/45R18 → 235/40R19
235/40R19
Diameter −1.6% · Good fit
225/45R18 → 245/35R19
245/35R19
Diameter +0.9% · Good fit
225/45R18 → 255/35R19
255/35R19
Diameter −0.2% · Good fit
225/45R18 → 205/65R16
205/65R16
Diameter −2.0% · Good fit
225/45R18 → 255/40R18
255/40R18
Diameter −0.2% · Good fit
225/45R18 → 255/45R18
255/45R18
Diameter −3.9% · Marginal fit — proceed with care
Common questions
- What is the overall diameter of a 225/45R18 tire?
- A 225/45R18 tire is about 25.97″ (660 mm) in overall diameter, with a sidewall height of 101.3 mm and a circumference of 81.59″.
- How many revolutions per mile does a 225/45R18 tire turn?
- A 225/45R18 turns roughly 777 revolutions per mile (483 per kilometre). This is the number that determines speedometer and odometer accuracy when you change tire size.
- What do the numbers in 225/45R18 mean?
- 225 is the tread width in millimetres, 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.