Tire Ruler305/50R20 dimensions
| Overall diameter (height) | 32.01″ · 813 mm |
| Section width | 12.01″ · 305 mm |
| Sidewall height | 6.00″ · 153 mm |
| Wheel diameter | 20″ |
| Rim width (rule of thumb) | 8.5–10.5″ |
| Circumference | 100.6″ |
| Revolutions per mile | 630 |
| In inches (flotation style) | 32.0 × 12.0R20 |
How it’s calculated: the sidewall is 50% of the 305 mm width = 152.5 mm (6.00″). Add two sidewalls to the 20″ wheel: 20 + 2 × 6.00 = 32.01″.
Bigger tires than 305/50R20 on 20″ wheels
| Size | Height | Taller by | 60 mph reads |
|---|---|---|---|
| 285/55R20 | 32.3″ | +0.33″ (+1.0%) | 60.6 mph |
| 265/60R20 | 32.5″ | +0.51″ (+1.6%) | 61.0 mph |
| 295/55R20 | 32.8″ | +0.77″ (+2.4%) | 61.4 mph |
| 275/60R20 | 33.0″ | +0.98″ (+3.1%) | 61.8 mph |
| 33x12.50R20 | 33.0″ | +0.99″ (+3.1%) | 61.9 mph |
“60 mph reads” is your real speed when a speedometer set up for 305/50R20 shows 60. Above about 3% taller, most trucks need a leveling kit or lift, and the speedometer should be recalibrated.
Sizes equivalent to 305/50R20
Within 1.5% of the same height on a 20″ wheel. Usually interchangeable for the speedometer; check width, load index and clearance.
| Size | Height | Width | Difference |
|---|---|---|---|
| 275/55R20 | 31.9″ | 10.8″ | −0.3% |
| 285/55R20 | 32.3″ | 11.2″ | +1.0% |
| 245/60R20 | 31.6″ | 9.6″ | −1.4% |
Same height on a different wheel size
Changing wheel size (plus or minus sizing) while keeping the overall height keeps your speedometer right:
- 32x11.50R15: 32.0″ tall on a 15″ wheel (−0.0%)
- 265/75R16: 31.6″ tall on a 16″ wheel (−1.1%)
- 235/85R16: 31.7″ tall on a 16″ wheel (−0.9%)
- 265/70R17: 31.6″ tall on a 17″ wheel (−1.3%)
- 275/70R17: 32.2″ tall on a 17″ wheel (+0.5%)
- 255/75R17: 32.1″ tall on a 17″ wheel (+0.2%)
- 275/65R18: 32.1″ tall on an 18″ wheel (+0.2%)
- 265/65R18: 31.6″ tall on an 18″ wheel (−1.4%)
- 255/70R18: 32.1″ tall on an 18″ wheel (+0.1%)
- 285/45R22: 32.1″ tall on a 22″ wheel (+0.3%)
- 275/45R22: 31.7″ tall on a 22″ wheel (−0.8%)
Popular 305/50R20 comparisons
Frequently asked questions
Is 305/50R20 a 32 inch tire?
Yes. 305/50R20 is 32.01 inches tall, so it's sold and talked about as a 32-inch tire.
What size is 305/50R20 in inches?
305/50R20 is 32.0 inches tall (overall diameter), 12.0 inches wide, with a 6.0 inch sidewall, and fits a 20 inch wheel.
What tire size is equivalent to 305/50R20?
Sizes within 1.5% of the same diameter on a 20" wheel: 275/55R20 (31.9"), 285/55R20 (32.3"), 245/60R20 (31.6"). Check load index and width before swapping.
What rim width fits 305/50R20?
As a rule of thumb, about 8.5–10.5 inches. The tire maker's spec sheet lists the approved range for each model.
How many revolutions per mile does 305/50R20 make?
About 630 revolutions per mile in theory (circumference 100.6 in). Real tires turn slightly more because they flatten under load.