Tire Ruler275/45R21 dimensions
| Overall diameter (height) | 30.74″ · 781 mm |
| Section width | 10.83″ · 275 mm |
| Sidewall height | 4.87″ · 124 mm |
| Wheel diameter | 21″ |
| Rim width (rule of thumb) | 7.5–9.5″ |
| Circumference | 96.6″ |
| Revolutions per mile | 656 |
| In inches (flotation style) | 30.7 × 10.8R21 |
How it’s calculated: the sidewall is 45% of the 275 mm width = 123.8 mm (4.87″). Add two sidewalls to the 21″ wheel: 21 + 2 × 4.87 = 30.74″.
Sizes equivalent to 275/45R21
Within 1.5% of the same height on a 21″ wheel. Usually interchangeable for the speedometer; check width, load index and clearance.
| Size | Height | Width | Difference |
|---|---|---|---|
| 265/45R21 | 30.4″ | 10.4″ | −1.2% |
Same height on a different wheel size
Changing wheel size (plus or minus sizing) while keeping the overall height keeps your speedometer right:
- 31x10.50R15: 31.0″ tall on a 15″ wheel (+0.8%)
- 245/75R16: 30.5″ tall on a 16″ wheel (−0.9%)
- 265/70R16: 30.6″ tall on a 16″ wheel (−0.4%)
- 215/85R16: 30.4″ tall on a 16″ wheel (−1.2%)
- 245/70R17: 30.5″ tall on a 17″ wheel (−0.8%)
- 255/70R17: 31.1″ tall on a 17″ wheel (+1.0%)
- 265/65R17: 30.6″ tall on a 17″ wheel (−0.6%)
- 275/65R17: 31.1″ tall on a 17″ wheel (+1.1%)
- 265/60R18: 30.5″ tall on an 18″ wheel (−0.7%)
- 255/65R18: 31.1″ tall on an 18″ wheel (+1.0%)
- 245/65R18: 30.5″ tall on an 18″ wheel (−0.7%)
- 275/60R18: 31.0″ tall on an 18″ wheel (+0.8%)
- 255/60R19: 31.0″ tall on a 19″ wheel (+1.0%)
- 265/50R20: 30.4″ tall on a 20″ wheel (−1.0%)
- 255/55R20: 31.0″ tall on a 20″ wheel (+1.0%)
- 275/50R20: 30.8″ tall on a 20″ wheel (+0.3%)
- 265/40R22: 30.3″ tall on a 22″ wheel (−1.3%)
- 285/40R22: 31.0″ tall on a 22″ wheel (+0.8%)
Frequently asked questions
Is 275/45R21 a 31 inch tire?
Not quite. 275/45R21 is 30.74 inches tall, between a 30 and a 31 inch tire.
What size is 275/45R21 in inches?
275/45R21 is 30.7 inches tall (overall diameter), 10.8 inches wide, with a 4.9 inch sidewall, and fits a 21 inch wheel.
What tire size is equivalent to 275/45R21?
Sizes within 1.5% of the same diameter on a 21" wheel: 265/45R21 (30.4"). Check load index and width before swapping.
What rim width fits 275/45R21?
As a rule of thumb, about 7.5–9.5 inches. The tire maker's spec sheet lists the approved range for each model.
How many revolutions per mile does 275/45R21 make?
About 656 revolutions per mile in theory (circumference 96.6 in). Real tires turn slightly more because they flatten under load.