155/85R18 tire size
155/85R18 is a metric size: 28.4" tall, 6.1" wide, on a 18" rim — about a 28.5x6.00R18. The sidewall is 5.2" and the tire turns 711 times per mile.
155/85R18 specs
| Overall diameter (height) | 28.37" · 721 mm |
|---|---|
| Section width | 6.10" · 155 mm |
| Sidewall height | 5.19" · 132 mm (85% of width) |
| Rim diameter | 18" |
| Circumference | 89.14" · 2.264 m |
| Revolutions per mile | 711 (442 per km) |
| Inch (flotation) equivalent | 28.5x6.00R18 |
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" | +2.57% | +80 mm | 61.5 mph | calculate → |
| 235/50R18 common | 27.25" | -3.95% | +80 mm | 57.6 mph | calculate → |
| 235/55R18 common | 28.18" | -0.69% | +80 mm | 59.6 mph | calculate → |
| 225/60R18 common | 28.63" | +0.90% | +70 mm | 60.5 mph | calculate → |
| 245/60R18 common | 29.57" | +4.23% | +90 mm | 62.5 mph | calculate → |
| 225/55R18 common | 27.74" | -2.22% | +70 mm | 58.7 mph | calculate → |
| 255/55R18 common | 29.04" | +2.36% | +100 mm | 61.4 mph | calculate → |
| 245/50R18 common | 27.65" | -2.57% | +90 mm | 58.5 mph | calculate → |
| 255/45R18 common | 27.04" | -4.72% | +100 mm | 57.2 mph | calculate → |
| 215/55R18 common | 27.31" | -3.75% | +60 mm | 57.8 mph | calculate → |
| 245/55R18 | 28.61" | +0.83% | +90 mm | 60.5 mph | calculate → |
| 275/45R18 | 27.74" | -2.22% | +120 mm | 58.7 mph | calculate → |
| 265/45R18 | 27.39" | -3.47% | +110 mm | 57.9 mph | calculate → |
| 295/40R18 | 27.29" | -3.82% | +140 mm | 57.7 mph | calculate → |
| 285/40R18 | 26.98" | -4.93% | +130 mm | 57.0 mph | calculate → |
| 345/35R18 | 27.51" | -3.05% | +190 mm | 58.2 mph | calculate → |
| 295/45R18 | 28.45" | +0.28% | +140 mm | 60.2 mph | calculate → |
| 255/50R18 | 28.04" | -1.18% | +100 mm | 59.3 mph | calculate → |
| 315/40R18 | 27.92" | -1.60% | +160 mm | 59.0 mph | calculate → |
| 155/90R18 | 28.98" | +2.15% | 0 mm | 61.3 mph | calculate → |
| 215/60R18 | 28.16" | -0.76% | +60 mm | 59.5 mph | calculate → |
| 305/45R18 | 28.81" | +1.53% | +150 mm | 60.9 mph | calculate → |
| 305/40R18 | 27.61" | -2.71% | +150 mm | 58.4 mph | calculate → |
| 285/50R18 | 29.22" | +2.98% | +130 mm | 61.8 mph | calculate → |
| 165/90R18 | 29.69" | +4.65% | +10 mm | 62.8 mph | calculate → |
| 285/45R18 | 28.10" | -0.97% | +130 mm | 59.4 mph | calculate → |
| 28x12.00R18 | 28.00" | -1.32% | +150 mm | 59.2 mph | calculate → |
| 145/85R18 | 27.70" | -2.36% | -10 mm | 58.6 mph | calculate → |
| 325/45R18 | 29.52" | +4.02% | +170 mm | 62.4 mph | calculate → |
| 145/80R18 | 27.13" | -4.37% | -10 mm | 57.4 mph | calculate → |
| 165/70R18 | 27.09" | -4.51% | +10 mm | 57.3 mph | calculate → |
| 325/35R18 | 26.96" | -5.00% | +170 mm | 57.0 mph | calculate → |
| 265/50R18 | 28.43" | +0.21% | +110 mm | 60.1 mph | calculate → |
| 28x10.00R18 | 28.00" | -1.32% | +99 mm | 59.2 mph | calculate → |
| 205/60R18 | 27.69" | -2.43% | +50 mm | 58.5 mph | calculate → |
| 265/55R18 | 29.48" | +3.89% | +110 mm | 62.3 mph | calculate → |
| 225/65R18 | 29.52" | +4.02% | +70 mm | 62.4 mph | calculate → |
| 195/60R18 | 27.21" | -4.09% | +40 mm | 57.5 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 | |
|---|---|---|---|---|---|
| 225/65R17 common | 28.52" | +0.50% | +70 mm | 60.3 mph | calculate → |
| 235/60R17 common | 28.10" | -0.96% | +80 mm | 59.4 mph | calculate → |
| 235/50R19 common | 28.25" | -0.43% | +80 mm | 59.7 mph | calculate → |
| 245/50R19 common | 28.65" | +0.96% | +90 mm | 60.6 mph | calculate → |
| 295/40R19 | 28.29" | -0.29% | +140 mm | 59.8 mph | calculate → |
| 265/45R19 | 28.39" | +0.06% | +110 mm | 60.0 mph | calculate → |
| 345/35R19 | 28.51" | +0.47% | +190 mm | 60.3 mph | calculate → |
| 245/60R17 | 28.57" | +0.71% | +90 mm | 60.4 mph | calculate → |
| 145/80R19 | 28.13" | -0.85% | -10 mm | 59.5 mph | calculate → |
Try another size against 155/85R18
Questions
What size is 155/85R18 in inches?
155/85R18 is about 28.4" tall and 6.1" wide on a 18-inch rim — roughly a 28.5x6.00R18 in inch sizing.
What does 155/85R18 mean?
155 mm section width, sidewall 85% of the width (5.19"), radial construction, 18-inch rim.
What tire sizes are equivalent to 155/85R18?
On the same 18" rim, within 3% of the diameter: 265/50R18 (+0.21%), 295/45R18 (+0.28%), 235/55R18 (-0.69%), 215/60R18 (-0.76%), 245/55R18 (+0.83%), 225/60R18 (+0.90%).
How many revolutions per mile does a 155/85R18 tire make?
About 711 revolutions per mile (circumference 89.1").
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.