Tire Ruler265/45R21 dimensions
| Overall diameter (height) | 30.39″ · 772 mm |
| Section width | 10.43″ · 265 mm |
| Sidewall height | 4.69″ · 119 mm |
| Wheel diameter | 21″ |
| Rim width (rule of thumb) | 7.5–9″ |
| Circumference | 95.5″ |
| Revolutions per mile | 664 |
| In inches (flotation style) | 30.4 × 10.4R21 |
How it’s calculated: the sidewall is 45% of the 265 mm width = 119.3 mm (4.69″). Add two sidewalls to the 21″ wheel: 21 + 2 × 4.69 = 30.39″.
Bigger tires than 265/45R21 on 21″ wheels
| Size | Height | Taller by | 60 mph reads |
|---|---|---|---|
| 275/45R21 | 30.7″ | +0.35″ (+1.2%) | 60.7 mph |
“60 mph reads” is your real speed when a speedometer set up for 265/45R21 shows 60. Above about 3% taller, most trucks need a leveling kit or lift, and the speedometer should be recalibrated.
Sizes equivalent to 265/45R21
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 |
|---|---|---|---|
| 275/45R21 | 30.7″ | 10.8″ | +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:
- 30x9.50R15: 30.0″ tall on a 15″ wheel (−1.3%)
- 245/75R16: 30.5″ tall on a 16″ wheel (+0.3%)
- 265/70R16: 30.6″ tall on a 16″ wheel (+0.7%)
- 255/70R16: 30.1″ tall on a 16″ wheel (−1.1%)
- 215/85R16: 30.4″ tall on a 16″ wheel (±0.0%)
- 245/70R17: 30.5″ tall on a 17″ wheel (+0.4%)
- 265/65R17: 30.6″ tall on a 17″ wheel (+0.6%)
- 255/65R17: 30.1″ tall on a 17″ wheel (−1.1%)
- 235/70R17: 30.0″ tall on a 17″ wheel (−1.4%)
- 265/60R18: 30.5″ tall on an 18″ wheel (+0.4%)
- 235/65R18: 30.0″ tall on an 18″ wheel (−1.2%)
- 245/65R18: 30.5″ tall on an 18″ wheel (+0.5%)
- 255/55R19: 30.0″ tall on a 19″ wheel (−1.1%)
- 265/50R20: 30.4″ tall on a 20″ wheel (+0.1%)
- 255/50R20: 30.0″ tall on a 20″ wheel (−1.2%)
- 275/50R20: 30.8″ tall on a 20″ wheel (+1.4%)
- 265/40R22: 30.3″ tall on a 22″ wheel (−0.1%)
Frequently asked questions
Is 265/45R21 a 30 inch tire?
Not quite. 265/45R21 is 30.39 inches tall, between a 30 and a 31 inch tire.
What size is 265/45R21 in inches?
265/45R21 is 30.4 inches tall (overall diameter), 10.4 inches wide, with a 4.7 inch sidewall, and fits a 21 inch wheel.
What tire size is equivalent to 265/45R21?
Sizes within 1.5% of the same diameter on a 21" wheel: 275/45R21 (30.7"). Check load index and width before swapping.
What rim width fits 265/45R21?
As a rule of thumb, about 7.5–9 inches. The tire maker's spec sheet lists the approved range for each model.
How many revolutions per mile does 265/45R21 make?
About 664 revolutions per mile in theory (circumference 95.5 in). Real tires turn slightly more because they flatten under load.