285/45R21
Overall diameter
31.10″
790 mm
Sidewall height
5.05″
128.3 mm
Tread width
285 mm
11.2″
Circumference
97.70″
8.1 ft
Revs per mile
649
403 per km
Wheel diameter
21″
aspect ratio 45%
Cross-section
- Overall diameter
- 31.10″
- Sidewall (each side)
- 5.05″
- Wheel
- 21″
285/45R21 compared with other sizes
All 26 practical swaps involving 285/45R21 — diameter change, speedometer impact and a fit verdict for each.
285/45R21 → 255/60R19
255/60R19
Diameter +0.2% · Good fit
285/45R21 → 275/55R19
275/55R19
Diameter +0.6% · Good fit
285/45R21 → 255/55R20
255/55R20
Diameter +0.2% · Good fit
285/45R21 → 265/55R20
265/55R20
Diameter −1.2% · Good fit
285/45R21 → 285/50R20
285/50R20
Diameter −0.4% · Good fit
285/45R21 → 265/45R21
265/45R21
Diameter +2.3% · Good fit
285/45R21 → 275/45R21
275/45R21
Diameter +1.2% · Good fit
285/45R21 → 275/50R21
275/50R21
Diameter −2.3% · Good fit
285/45R21 → 285/40R21
285/40R21
Diameter +3.7% · Marginal fit — proceed with care
275/45R21 → 285/45R21
275/45R21
Diameter −1.1% · Good fit
265/45R21 → 285/45R21
265/45R21
Diameter −2.3% · Good fit
275/50R21 → 285/45R21
275/50R21
Diameter +2.3% · Good fit
285/40R21 → 285/45R21
285/40R21
Diameter −3.6% · Marginal fit — proceed with care
285/50R20 → 285/45R21
285/50R20
Diameter +0.4% · Good fit
285/40R22 → 285/45R21
285/40R22
Diameter −0.4% · Good fit
255/60R19 → 285/45R21
255/60R19
Diameter −0.2% · Good fit
255/55R20 → 285/45R21
255/55R20
Diameter −0.2% · Good fit
275/55R19 → 285/45R21
275/55R19
Diameter −0.6% · Good fit
265/55R20 → 285/45R21
265/55R20
Diameter +1.2% · Good fit
275/40R22 → 285/45R21
275/40R22
Diameter −1.4% · Good fit
285/45R22 → 285/45R21
285/45R22
Diameter +3.2% · Marginal fit — proceed with care
265/55R19 → 285/45R21
265/55R19
Diameter −2.0% · Good fit
265/50R20 → 285/45R21
265/50R20
Diameter −2.1% · Good fit
285/45R21 → 275/40R22
275/40R22
Diameter +1.4% · Good fit
285/45R21 → 285/40R22
285/40R22
Diameter +0.4% · Good fit
285/45R21 → 285/45R22
285/45R22
Diameter −3.1% · Marginal fit — proceed with care
Common questions
- What is the overall diameter of a 285/45R21 tire?
- A 285/45R21 tire is about 31.10″ (790 mm) in overall diameter, with a sidewall height of 128.3 mm and a circumference of 97.70″.
- How many revolutions per mile does a 285/45R21 tire turn?
- A 285/45R21 turns roughly 649 revolutions per mile (403 per kilometre). This is the number that determines speedometer and odometer accuracy when you change tire size.
- What do the numbers in 285/45R21 mean?
- 285 is the tread width in millimetres, 45 is the aspect ratio — the sidewall height as a percentage of the tread width — and 21 is the wheel diameter in inches. So the sidewall is 285 × 45% = 128.3 mm tall.