33x12.5R20 Tire Size
33x12.5R20 diameter, sidewall, revolutions per mile, and plus-sizing options.
The 33x12.5R20 tire size breaks down as: 318 mm section width, 52% aspect ratio, and a 20-inch rim. Below are its real, calculated dimensions.
33x12.5R20 Calculated Dimensions
| Metric | Value |
|---|---|
| Overall diameter | 33.0 in (838 mm) |
| Sidewall height | 6.5 in (165 mm) |
| Circumference | 103.7 in (2633 mm) |
| Revolutions per mile | 611 |
Typical Fitment
33x12.5R20 is most often found on lifted trucks and SUVs. Always confirm against the door-jamb placard or owner manual before fitting.
Plus-Sizing Alternatives
These sizes keep the overall diameter close to 33x12.5R20, so speedometer and gearing stay near stock:
| Size | Diameter | Diameter change |
|---|---|---|
| 327.5/50R20 | 32.89 in | -0.3% |
| 327.5/45R21 | 32.60 in | -1.2% |
| 337.5/40R22 | 32.63 in | -1.1% |
Speedometer Note
If you fit a 327.5/50R20 instead of 33x12.5R20, the diameter changes by -0.3%. A taller tire makes your speedometer read low — at a true 60 mph it would show roughly 60 mph. A shorter tire has the opposite effect, so the gauge reads high.
Use the tire calculator to compare 33x12.5R20 against any other size and see the exact diameter and speedometer difference.
Frequently Asked Questions
What does 33x12.5R20 mean?
33x12.5R20 means a 318 mm wide tire with a 52% sidewall aspect ratio mounted on a 20-inch rim. The aspect ratio is the sidewall height as a percentage of the width.
Can I plus-size from 33x12.5R20?
Yes, as long as the replacement keeps the overall diameter close to stock so the speedometer stays accurate. Common plus-size moves from 33x12.5R20 are 327.5/50R20, 327.5/45R21, 337.5/40R22.
Will 33x12.5R20 affect my speedometer?
Only if it differs in diameter from your original size. A taller tire reads low; a shorter tire reads high. Compare the two sizes with the calculator to find the percentage.