285/40R21
A 285/40R21 tire is 29.98 inches tall and 11.2 inches wide, with a 4.49-inch sidewall, mounted on a 21-inch wheel.
Overall diameter
29.98″
761 mm
Sidewall height
4.49″
114.0 mm
Tread width
285 mm
11.2″
Circumference
94.17″
7.8 ft
Revs per mile
673
418 per km
Wheel diameter
21″
aspect ratio 40%
Cross-section
- Overall diameter
- 29.98″
- Sidewall (each side)
- 4.49″
- Wheel
- 21″
285/40R21 in inches and millimeters
Every dimension of a 285/40R21, converted both ways. Calculated from the size code, accurate to about 1%.
| Measurement | Inches | Millimeters |
|---|---|---|
| Overall diameter (height) | 29.98″ | 761 mm |
| Tread width | 11.2″ | 285 mm |
| Sidewall height | 4.49″ | 114.0 mm |
| Wheel diameter | 21″ | 533 mm |
| Circumference | 94.17″ | 2392 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.
285/40R21 compared with other sizes
All 23 practical swaps involving 285/40R21 — diameter change, speedometer impact and a fit verdict for each.
285/40R21 → 275/45R20
275/45R20
Diameter +0.8% · This fits
285/40R21 → 245/50R20
245/50R20
Diameter +1.1% · This fits
285/40R21 → 255/50R20
255/50R20
Diameter −0.2% · This fits
285/40R21 → 265/40R21
265/40R21
Diameter +2.1% · This fits
285/40R21 → 265/45R21
265/45R21
Diameter −1.4% · This fits
285/40R21 → 275/45R21
275/45R21
Diameter −2.5% · This fits
265/45R21 → 285/40R21
265/45R21
Diameter +1.4% · This fits
265/40R21 → 285/40R21
265/40R21
Diameter −2.1% · This fits
285/45R21 → 285/40R21
285/45R21
Diameter +3.7% · Borderline. Check clearance first
275/45R21 → 285/40R21
275/45R21
Diameter +2.6% · This fits
255/50R20 → 285/40R21
255/50R20
Diameter +0.2% · This fits
275/45R20 → 285/40R21
275/45R20
Diameter −0.8% · This fits
245/50R20 → 285/40R21
245/50R20
Diameter −1.1% · This fits
245/55R19 → 285/40R21
245/55R19
Diameter −1.2% · This fits
265/50R20 → 285/40R21
265/50R20
Diameter +1.5% · This fits
265/55R19 → 285/40R21
265/55R19
Diameter +1.7% · This fits
265/50R19 → 285/40R21
265/50R19
Diameter −1.8% · This fits
265/45R20 → 285/40R21
265/45R20
Diameter −2.0% · This fits
285/40R22 → 285/40R21
285/40R22
Diameter +3.3% · Borderline. Check clearance first
275/40R22 → 285/40R21
275/40R22
Diameter +2.3% · This fits
285/40R21 → 285/45R21
285/45R21
Diameter −3.6% · Borderline. Check clearance first
285/40R21 → 275/40R22
275/40R22
Diameter −2.2% · This fits
285/40R21 → 285/40R22
285/40R22
Diameter −3.2% · Borderline. Check clearance first
Common questions
- What is 285/40R21 in inches?
- A 285/40R21 tire is 29.98 inches tall and 11.2 inches wide, with a 4.49-inch sidewall, mounted on a 21-inch wheel. In metric that is 761 mm tall and 285 mm wide. The circumference is 94.17 inches.
- How tall is a 285/40R21 tire?
- 29.98 inches, or 761 mm. That is the overall diameter, wheel included. It turns about 673 times per mile, which is what your speedometer counts.
- What do the numbers in 285/40R21 mean?
- 285 is the tread width in millimeters, 40 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 × 40% = 114.0 mm tall.