38x15.50R18 tire size
38x15.50R18 is a flotation (inch) size: 38.0" tall, 15.5" wide, on a 18" rim — about a 390/65R18. The sidewall is 10.0" and the tire turns 531 times per mile.
38x15.50R18 specs
| Overall diameter (height) | 38.00" · 965 mm |
|---|---|
| Section width | 15.50" · 394 mm |
| Sidewall height | 10.00" · 254 mm (65% of width) |
| Rim diameter | 18" |
| Circumference | 119.38" · 3.032 m |
| Revolutions per mile | 531 (330 per km) |
| Closest metric size | 390/65R18 |
Equivalent sizes on a 18" rim
Sizes within ±5% of the overall diameter. Green rows are inside the usual ±3% limit for keeping the speedometer, ABS and gearing right; red rows are bigger changes that need clearance checks.
| Size | Diameter | Difference | Width | Speedo at 60 | |
|---|---|---|---|---|---|
| 37x13.50R18 | 37.00" | -2.63% | -51 mm | 58.4 mph | calculate → |
| 37x12.50R18 | 37.00" | -2.63% | -76 mm | 58.4 mph | calculate → |
| 38x13.50R18 | 38.00" | 0.00% | -51 mm | 60.0 mph | calculate → |
| 38x11.50R18 | 38.00" | 0.00% | -102 mm | 60.0 mph | calculate → |
| 38x14.50R18 | 38.00" | 0.00% | -26 mm | 60.0 mph | calculate → |
| 38.5x14.50R18 | 38.50" | +1.32% | -26 mm | 60.8 mph | calculate → |
| 37x11.50R18 | 37.00" | -2.63% | -102 mm | 58.4 mph | calculate → |
| 38x15.00R18 | 38.00" | 0.00% | -13 mm | 60.0 mph | calculate → |
| 37x14.50R18 | 37.00" | -2.63% | -26 mm | 58.4 mph | calculate → |
| 355/65R18 | 36.17" | -4.82% | -39 mm | 57.1 mph | calculate → |
Plus / minus sizing: 17" and 19" rims
Same overall height on a different rim. Check wheel width and clearance before switching.
| Size | Diameter | Difference | Width | Speedo at 60 | |
|---|---|---|---|---|---|
| 38x13.50R17 | 38.00" | 0.00% | -51 mm | 60.0 mph | calculate → |
| 38x11.50R17 | 38.00" | 0.00% | -102 mm | 60.0 mph | calculate → |
| 38x12.50R17 | 38.00" | 0.00% | -76 mm | 60.0 mph | calculate → |
| 38x14.50R17 | 38.00" | 0.00% | -26 mm | 60.0 mph | calculate → |
| 38x15.50R17 | 38.00" | 0.00% | 0 mm | 60.0 mph | calculate → |
Try another size against 38x15.50R18
Questions
What size is 38x15.50R18 in inches?
38x15.50R18 is about 38.0" tall and 15.5" wide on a 18-inch rim — roughly a 390/65R18 in inch sizing.
What does 38x15.50R18 mean?
38" overall diameter, 15.50" section width, radial, 18" rim.
What tire sizes are equivalent to 38x15.50R18?
On the same 18" rim, within 3% of the diameter: 38x11.50R18 (0.00%), 38x13.50R18 (0.00%), 38x14.50R18 (0.00%), 38x15.00R18 (0.00%), 38.5x14.50R18 (+1.32%), 37x11.50R18 (-2.63%).
How many revolutions per mile does a 38x15.50R18 tire make?
About 531 revolutions per mile (circumference 119.4").
How these numbers are computed
Diameter = rim + 2 × sidewall, sidewall = width × aspect ÷ 100, circumference = π × diameter, revolutions per mile = 63,360 ÷ circumference. Real tires differ by brand by a few tenths of an inch. Last reviewed October 14, 2026.