255/45R18 tire size
255/45R18 is a metric size: 27.0" tall, 10.0" wide, on a 18" rim — about a 27x10.00R18. The sidewall is 4.5" and the tire turns 746 times per mile.
255/45R18 specs
| Overall diameter (height) | 27.04" · 687 mm |
|---|---|
| Section width | 10.04" · 255 mm |
| Sidewall height | 4.52" · 115 mm (45% of width) |
| Rim diameter | 18" |
| Circumference | 84.93" · 2.157 m |
| Revolutions per mile | 746 (464 per km) |
| Inch (flotation) equivalent | 27x10.00R18 |
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 | |
|---|---|---|---|---|---|
| 225/45R18 common | 25.97" | -3.93% | -30 mm | 57.6 mph | compare → |
| 245/40R18 common | 25.72" | -4.88% | -10 mm | 57.1 mph | compare → |
| 245/45R18 common | 26.68" | -1.31% | -10 mm | 59.2 mph | compare → |
| 235/50R18 common | 27.25" | +0.80% | -20 mm | 60.5 mph | compare → |
| 235/45R18 common | 26.33" | -2.62% | -20 mm | 58.4 mph | compare → |
| 235/55R18 common | 28.18" | +4.22% | -20 mm | 62.5 mph | compare → |
| 225/50R18 common | 26.86" | -0.66% | -30 mm | 59.6 mph | compare → |
| 225/55R18 common | 27.74" | +2.62% | -30 mm | 61.6 mph | compare → |
| 255/40R18 common | 26.03" | -3.71% | 0 mm | 57.8 mph | compare → |
| 245/50R18 common | 27.65" | +2.26% | -10 mm | 61.4 mph | compare → |
| 215/55R18 common | 27.31" | +1.02% | -40 mm | 60.6 mph | compare → |
| 275/40R18 common | 26.66" | -1.38% | +20 mm | 59.2 mph | compare → |
| 265/40R18 | 26.35" | -2.55% | +10 mm | 58.5 mph | compare → |
| 285/35R18 | 25.85" | -4.37% | +30 mm | 57.4 mph | compare → |
| 295/35R18 | 26.13" | -3.35% | +40 mm | 58.0 mph | compare → |
| 335/30R18 | 25.91" | -4.15% | +80 mm | 57.5 mph | compare → |
| 275/45R18 | 27.74" | +2.62% | +20 mm | 61.6 mph | compare → |
| 215/50R18 | 26.46" | -2.11% | -40 mm | 58.7 mph | compare → |
| 295/40R18 | 27.29" | +0.95% | +40 mm | 60.6 mph | compare → |
| 265/45R18 | 27.39" | +1.31% | +10 mm | 60.8 mph | compare → |
| 285/40R18 | 26.98" | -0.22% | +30 mm | 59.9 mph | calculate → |
| 345/35R18 | 27.51" | +1.75% | +90 mm | 61.0 mph | calculate → |
| 305/35R18 | 26.41" | -2.33% | +50 mm | 58.6 mph | calculate → |
| 255/50R18 | 28.04" | +3.71% | 0 mm | 62.2 mph | calculate → |
| 315/40R18 | 27.92" | +3.28% | +60 mm | 62.0 mph | calculate → |
| 305/40R18 | 27.61" | +2.11% | +50 mm | 61.3 mph | calculate → |
| 215/60R18 | 28.16" | +4.15% | -40 mm | 62.5 mph | calculate → |
| 155/85R18 | 28.37" | +4.95% | -100 mm | 63.0 mph | calculate → |
| 165/70R18 | 27.09" | +0.22% | -90 mm | 60.1 mph | calculate → |
| 325/35R18 | 26.96" | -0.29% | +70 mm | 59.8 mph | calculate → |
| 145/80R18 | 27.13" | +0.36% | -110 mm | 60.2 mph | calculate → |
| 155/70R18 | 26.54" | -1.82% | -100 mm | 58.9 mph | calculate → |
| 145/85R18 | 27.70" | +2.48% | -110 mm | 61.5 mph | calculate → |
| 28x12.00R18 | 28.00" | +3.57% | +50 mm | 62.1 mph | calculate → |
| 26x12.00R18 | 26.00" | -3.83% | +50 mm | 57.7 mph | calculate → |
| 26x6.00R18 | 26.00" | -3.83% | -103 mm | 57.7 mph | calculate → |
| 26x8.00R18 | 26.00" | -3.83% | -52 mm | 57.7 mph | calculate → |
| 145/70R18 | 25.99" | -3.86% | -110 mm | 57.7 mph | calculate → |
| 285/45R18 | 28.10" | +3.93% | +30 mm | 62.4 mph | calculate → |
| 195/60R18 | 27.21" | +0.66% | -60 mm | 60.4 mph | calculate → |
| 315/35R18 | 26.68" | -1.31% | +60 mm | 59.2 mph | calculate → |
| 205/60R18 | 27.69" | +2.40% | -50 mm | 61.4 mph | calculate → |
| 345/30R18 | 26.15" | -3.28% | +90 mm | 58.0 mph | calculate → |
| 28x10.00R18 | 28.00" | +3.57% | -1 mm | 62.1 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 | |
|---|---|---|---|---|---|
| 235/55R17 common | 27.18" | +0.52% | -20 mm | 60.3 mph | compare → |
| 255/40R19 common | 27.03" | -0.01% | 0 mm | 60.0 mph | compare → |
| 215/60R17 common | 27.16" | +0.45% | -40 mm | 60.3 mph | compare → |
| 225/45R19 common | 26.97" | -0.23% | -30 mm | 59.9 mph | compare → |
| 285/35R19 common | 26.85" | -0.67% | +30 mm | 59.6 mph | compare → |
| 295/35R19 | 27.13" | +0.35% | +40 mm | 60.2 mph | compare → |
| 345/30R19 | 27.15" | +0.42% | +90 mm | 60.3 mph | compare → |
| 255/50R17 | 27.04" | +0.01% | 0 mm | 60.0 mph | calculate → |
| 175/60R19 | 27.27" | +0.86% | -80 mm | 60.5 mph | calculate → |
| 335/30R19 | 26.91" | -0.45% | +80 mm | 59.7 mph | calculate → |
| 145/90R17 | 27.28" | +0.89% | -110 mm | 60.5 mph | calculate → |
Try another size against 255/45R18
Questions
What size is 255/45R18 in inches?
255/45R18 is about 27.0" tall and 10.0" wide on a 18-inch rim — roughly a 27x10.00R18 in inch sizing.
What does 255/45R18 mean?
255 mm section width, sidewall 45% of the width (4.52"), radial construction, 18-inch rim.
What tire sizes are equivalent to 255/45R18?
On the same 18" rim, within 3% of the diameter: 165/70R18 (+0.22%), 285/40R18 (-0.22%), 325/35R18 (-0.29%), 145/80R18 (+0.36%), 225/50R18 (-0.66%), 195/60R18 (+0.66%).
How many revolutions per mile does a 255/45R18 tire make?
About 746 revolutions per mile (circumference 84.9").
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.