37x12.50R18 tire size
37x12.50R18 is a flotation (inch) size: 37.0" tall, 12.5" wide, on a 18" rim — about a 320/75R18. The sidewall is 9.5" and the tire turns 545 times per mile.
37x12.50R18 specs
| Overall diameter (height) | 37.00" · 940 mm |
|---|---|
| Section width | 12.50" · 318 mm |
| Sidewall height | 9.50" · 241 mm (76% of width) |
| Rim diameter | 18" |
| Circumference | 116.24" · 2.952 m |
| Revolutions per mile | 545 (339 per km) |
| Closest metric size | 320/75R18 |
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" | 0.00% | +25 mm | 60.0 mph | compare → |
| 38x15.50R18 | 38.00" | +2.70% | +76 mm | 61.6 mph | calculate → |
| 38x13.50R18 | 38.00" | +2.70% | +25 mm | 61.6 mph | calculate → |
| 315/70R18 | 35.36" | -4.43% | -3 mm | 57.3 mph | calculate → |
| 37x11.50R18 | 37.00" | 0.00% | -26 mm | 60.0 mph | calculate → |
| 36x13.50R18 | 36.00" | -2.70% | +25 mm | 58.4 mph | calculate → |
| 38x11.50R18 | 38.00" | +2.70% | -26 mm | 61.6 mph | calculate → |
| 38x14.50R18 | 38.00" | +2.70% | +50 mm | 61.6 mph | calculate → |
| 38.5x14.50R18 | 38.50" | +4.05% | +50 mm | 62.4 mph | calculate → |
| 37x14.50R18 | 37.00" | 0.00% | +50 mm | 60.0 mph | calculate → |
| 355/65R18 | 36.17" | -2.25% | +37 mm | 58.7 mph | calculate → |
| 38x15.00R18 | 38.00" | +2.70% | +63 mm | 61.6 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 | |
|---|---|---|---|---|---|
| 37x12.50R17 common | 37.00" | 0.00% | 0 mm | 60.0 mph | compare → |
| 37x13.50R17 | 37.00" | 0.00% | +25 mm | 60.0 mph | compare → |
| 37x11.50R17 | 37.00" | 0.00% | -26 mm | 60.0 mph | calculate → |
| 37x13.00R17 | 37.00" | 0.00% | +12 mm | 60.0 mph | calculate → |
| 37x14.00R17 | 37.00" | 0.00% | +38 mm | 60.0 mph | calculate → |
Try another size against 37x12.50R18
Questions
What size is 37x12.50R18 in inches?
37x12.50R18 is about 37.0" tall and 12.5" wide on a 18-inch rim — roughly a 320/75R18 in inch sizing.
What does 37x12.50R18 mean?
37" overall diameter, 12.50" section width, radial, 18" rim.
What tire sizes are equivalent to 37x12.50R18?
On the same 18" rim, within 3% of the diameter: 37x11.50R18 (0.00%), 37x13.50R18 (0.00%), 37x14.50R18 (0.00%), 355/65R18 (-2.25%), 36x13.50R18 (-2.70%), 38x11.50R18 (+2.70%).
How many revolutions per mile does a 37x12.50R18 tire make?
About 545 revolutions per mile (circumference 116.2").
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.