175/90R18 tire size
175/90R18 is a metric size: 30.4" tall, 6.9" wide, on a 18" rim — about a 30.5x7.00R18. The sidewall is 6.2" and the tire turns 663 times per mile.
175/90R18 specs
| Overall diameter (height) | 30.40" · 772 mm |
|---|---|
| Section width | 6.89" · 175 mm |
| Sidewall height | 6.20" · 158 mm (90% of width) |
| Rim diameter | 18" |
| Circumference | 95.51" · 2.426 m |
| Revolutions per mile | 663 (412 per km) |
| Inch (flotation) equivalent | 30.5x7.00R18 |
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 | |
|---|---|---|---|---|---|
| 235/60R18 common | 29.10" | -4.27% | +60 mm | 57.4 mph | calculate → |
| 265/60R18 common | 30.52" | +0.39% | +90 mm | 60.2 mph | calculate → |
| 245/60R18 common | 29.57" | -2.72% | +70 mm | 58.4 mph | calculate → |
| 255/55R18 common | 29.04" | -4.47% | +80 mm | 57.3 mph | calculate → |
| 265/65R18 common | 31.56" | +3.82% | +90 mm | 62.3 mph | calculate → |
| 235/65R18 common | 30.03" | -1.23% | +60 mm | 59.3 mph | calculate → |
| 255/65R18 common | 31.05" | +2.14% | +80 mm | 61.3 mph | calculate → |
| 255/60R18 | 30.05" | -1.17% | +80 mm | 59.3 mph | calculate → |
| 285/60R18 | 31.46" | +3.50% | +110 mm | 62.1 mph | calculate → |
| 275/60R18 | 30.99" | +1.94% | +100 mm | 61.2 mph | calculate → |
| 155/90R18 | 28.98" | -4.66% | -20 mm | 57.2 mph | calculate → |
| 165/90R18 | 29.69" | -2.33% | -10 mm | 58.6 mph | calculate → |
| 245/70R18 | 31.50" | +3.63% | +70 mm | 62.2 mph | calculate → |
| 285/50R18 | 29.22" | -3.89% | +110 mm | 57.7 mph | calculate → |
| 285/55R18 | 30.34" | -0.19% | +110 mm | 59.9 mph | calculate → |
| 245/65R18 | 30.54" | +0.45% | +70 mm | 60.3 mph | calculate → |
| 275/55R18 | 29.91" | -1.62% | +100 mm | 59.0 mph | calculate → |
| 235/70R18 | 30.95" | +1.81% | +60 mm | 61.1 mph | calculate → |
| 325/45R18 | 29.52" | -2.91% | +150 mm | 58.3 mph | calculate → |
| 225/65R18 | 29.52" | -2.91% | +50 mm | 58.3 mph | calculate → |
| 265/55R18 | 29.48" | -3.04% | +90 mm | 58.2 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 | |
|---|---|---|---|---|---|
| 245/70R17 common | 30.50" | +0.34% | +70 mm | 60.2 mph | calculate → |
| 265/65R17 common | 30.56" | +0.53% | +90 mm | 60.3 mph | calculate → |
| 265/55R19 | 30.48" | +0.25% | +90 mm | 60.1 mph | calculate → |
| 225/75R17 | 30.29" | -0.38% | +50 mm | 59.8 mph | calculate → |
| 235/60R19 | 30.10" | -0.98% | +60 mm | 59.4 mph | calculate → |
| 315/55R17 | 30.64" | +0.79% | +140 mm | 60.5 mph | calculate → |
| 165/90R19 | 30.69" | +0.96% | -10 mm | 60.6 mph | calculate → |
| 285/60R17 | 30.46" | +0.21% | +110 mm | 60.1 mph | calculate → |
Try another size against 175/90R18
Questions
What size is 175/90R18 in inches?
175/90R18 is about 30.4" tall and 6.9" wide on a 18-inch rim — roughly a 30.5x7.00R18 in inch sizing.
What does 175/90R18 mean?
175 mm section width, sidewall 90% of the width (6.20"), radial construction, 18-inch rim.
What tire sizes are equivalent to 175/90R18?
On the same 18" rim, within 3% of the diameter: 285/55R18 (-0.19%), 265/60R18 (+0.39%), 245/65R18 (+0.45%), 255/60R18 (-1.17%), 235/65R18 (-1.23%), 275/55R18 (-1.62%).
How many revolutions per mile does a 175/90R18 tire make?
About 663 revolutions per mile (circumference 95.5").
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.