145/85R18 tire size
145/85R18 is a metric size: 27.7" tall, 5.7" wide, on a 18" rim — about a 27.5x5.50R18. The sidewall is 4.9" and the tire turns 728 times per mile.
145/85R18 specs
| Overall diameter (height) | 27.70" · 704 mm |
|---|---|
| Section width | 5.71" · 145 mm |
| Sidewall height | 4.85" · 123 mm (85% of width) |
| Rim diameter | 18" |
| Circumference | 87.04" · 2.211 m |
| Revolutions per mile | 728 (452 per km) |
| Inch (flotation) equivalent | 27.5x5.50R18 |
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 | |
|---|---|---|---|---|---|
| 245/45R18 common | 26.68" | -3.69% | +100 mm | 57.8 mph | calculate → |
| 235/50R18 common | 27.25" | -1.63% | +90 mm | 59.0 mph | calculate → |
| 235/55R18 common | 28.18" | +1.71% | +90 mm | 61.0 mph | calculate → |
| 235/45R18 common | 26.33" | -4.97% | +90 mm | 57.0 mph | calculate → |
| 225/60R18 common | 28.63" | +3.34% | +80 mm | 62.0 mph | calculate → |
| 225/50R18 common | 26.86" | -3.06% | +80 mm | 58.2 mph | calculate → |
| 225/55R18 common | 27.74" | +0.14% | +80 mm | 60.1 mph | calculate → |
| 255/55R18 common | 29.04" | +4.83% | +110 mm | 62.9 mph | calculate → |
| 245/50R18 common | 27.65" | -0.21% | +100 mm | 59.9 mph | calculate → |
| 255/45R18 common | 27.04" | -2.42% | +110 mm | 58.6 mph | calculate → |
| 215/55R18 common | 27.31" | -1.42% | +70 mm | 59.1 mph | calculate → |
| 275/40R18 common | 26.66" | -3.77% | +130 mm | 57.7 mph | calculate → |
| 245/55R18 | 28.61" | +3.27% | +100 mm | 62.0 mph | calculate → |
| 265/40R18 | 26.35" | -4.90% | +120 mm | 57.1 mph | calculate → |
| 275/45R18 | 27.74" | +0.14% | +130 mm | 60.1 mph | calculate → |
| 215/50R18 | 26.46" | -4.48% | +70 mm | 57.3 mph | calculate → |
| 265/45R18 | 27.39" | -1.14% | +120 mm | 59.3 mph | calculate → |
| 295/40R18 | 27.29" | -1.49% | +150 mm | 59.1 mph | calculate → |
| 285/40R18 | 26.98" | -2.63% | +140 mm | 58.4 mph | calculate → |
| 345/35R18 | 27.51" | -0.71% | +200 mm | 59.6 mph | calculate → |
| 305/35R18 | 26.41" | -4.69% | +160 mm | 57.2 mph | calculate → |
| 295/45R18 | 28.45" | +2.70% | +150 mm | 61.6 mph | calculate → |
| 255/50R18 | 28.04" | +1.21% | +110 mm | 60.7 mph | calculate → |
| 315/40R18 | 27.92" | +0.78% | +170 mm | 60.5 mph | calculate → |
| 155/90R18 | 28.98" | +4.62% | +10 mm | 62.8 mph | calculate → |
| 305/40R18 | 27.61" | -0.36% | +160 mm | 59.8 mph | calculate → |
| 215/60R18 | 28.16" | +1.63% | +70 mm | 61.0 mph | calculate → |
| 155/85R18 | 28.37" | +2.42% | +10 mm | 61.4 mph | calculate → |
| 305/45R18 | 28.81" | +3.98% | +160 mm | 62.4 mph | calculate → |
| 28x12.00R18 | 28.00" | +1.07% | +160 mm | 60.6 mph | calculate → |
| 285/45R18 | 28.10" | +1.42% | +140 mm | 60.9 mph | calculate → |
| 145/80R18 | 27.13" | -2.06% | 0 mm | 58.8 mph | calculate → |
| 165/70R18 | 27.09" | -2.20% | +20 mm | 58.7 mph | calculate → |
| 325/35R18 | 26.96" | -2.70% | +180 mm | 58.4 mph | calculate → |
| 155/70R18 | 26.54" | -4.19% | +10 mm | 57.5 mph | calculate → |
| 205/60R18 | 27.69" | -0.07% | +60 mm | 60.0 mph | calculate → |
| 28x10.00R18 | 28.00" | +1.07% | +109 mm | 60.6 mph | calculate → |
| 195/60R18 | 27.21" | -1.78% | +50 mm | 58.9 mph | calculate → |
| 265/50R18 | 28.43" | +2.63% | +120 mm | 61.6 mph | calculate → |
| 315/35R18 | 26.68" | -3.69% | +170 mm | 57.8 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 | |
|---|---|---|---|---|---|
| 245/45R19 common | 27.68" | -0.09% | +100 mm | 59.9 mph | calculate → |
| 225/60R17 common | 27.63" | -0.27% | +80 mm | 59.8 mph | calculate → |
| 275/40R19 common | 27.66" | -0.16% | +130 mm | 59.9 mph | calculate → |
| 285/40R19 | 27.98" | +0.98% | +140 mm | 60.6 mph | calculate → |
| 245/55R17 | 27.61" | -0.34% | +100 mm | 59.8 mph | calculate → |
| 155/70R19 | 27.54" | -0.58% | +10 mm | 59.7 mph | calculate → |
| 305/45R17 | 27.81" | +0.37% | +160 mm | 60.2 mph | calculate → |
| 215/50R19 | 27.46" | -0.87% | +70 mm | 59.5 mph | calculate → |
| 315/35R19 | 27.68" | -0.09% | +170 mm | 59.9 mph | calculate → |
| 275/50R17 | 27.83" | +0.44% | +130 mm | 60.3 mph | calculate → |
| 225/50R19 | 27.86" | +0.55% | +80 mm | 60.3 mph | calculate → |
| 345/40R17 | 27.87" | +0.58% | +200 mm | 60.3 mph | calculate → |
| 205/65R17 | 27.49" | -0.77% | +60 mm | 59.5 mph | calculate → |
Try another size against 145/85R18
Questions
What size is 145/85R18 in inches?
145/85R18 is about 27.7" tall and 5.7" wide on a 18-inch rim — roughly a 27.5x5.50R18 in inch sizing.
What does 145/85R18 mean?
145 mm section width, sidewall 85% of the width (4.85"), radial construction, 18-inch rim.
What tire sizes are equivalent to 145/85R18?
On the same 18" rim, within 3% of the diameter: 205/60R18 (-0.07%), 225/55R18 (+0.14%), 275/45R18 (+0.14%), 245/50R18 (-0.21%), 305/40R18 (-0.36%), 345/35R18 (-0.71%).
How many revolutions per mile does a 145/85R18 tire make?
About 728 revolutions per mile (circumference 87.0").
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.