205/45R18 tire size
205/45R18 is a metric size: 25.3" tall, 8.1" wide, on a 18" rim — about a 25.5x8.00R18. The sidewall is 3.6" and the tire turns 798 times per mile.
205/45R18 specs
| Overall diameter (height) | 25.26" · 642 mm |
|---|---|
| Section width | 8.07" · 205 mm |
| Sidewall height | 3.63" · 92 mm (45% of width) |
| Rim diameter | 18" |
| Circumference | 79.37" · 2.016 m |
| Revolutions per mile | 798 (496 per km) |
| Inch (flotation) equivalent | 25.5x8.00R18 |
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 | |
|---|---|---|---|---|---|
| 245/40R18 common | 25.72" | +1.79% | +40 mm | 61.1 mph | calculate → |
| 225/45R18 common | 25.97" | +2.81% | +20 mm | 61.7 mph | calculate → |
| 225/40R18 common | 25.09" | -0.70% | +20 mm | 59.6 mph | calculate → |
| 235/45R18 common | 26.33" | +4.21% | +30 mm | 62.5 mph | calculate → |
| 235/40R18 common | 25.40" | +0.55% | +30 mm | 60.3 mph | calculate → |
| 255/35R18 common | 25.03" | -0.94% | +50 mm | 59.4 mph | calculate → |
| 255/40R18 common | 26.03" | +3.04% | +50 mm | 61.8 mph | calculate → |
| 275/35R18 common | 25.58" | +1.25% | +70 mm | 60.7 mph | calculate → |
| 265/35R18 common | 25.30" | +0.16% | +60 mm | 60.1 mph | calculate → |
| 215/45R18 common | 25.62" | +1.40% | +10 mm | 60.8 mph | calculate → |
| 245/35R18 common | 24.75" | -2.03% | +40 mm | 58.8 mph | calculate → |
| 215/40R18 | 24.77" | -1.95% | +10 mm | 58.8 mph | calculate → |
| 285/35R18 | 25.85" | +2.34% | +80 mm | 61.4 mph | calculate → |
| 265/40R18 | 26.35" | +4.29% | +60 mm | 62.6 mph | calculate → |
| 295/30R18 | 24.97" | -1.17% | +90 mm | 59.3 mph | calculate → |
| 315/30R18 | 25.44" | +0.70% | +110 mm | 60.4 mph | calculate → |
| 285/30R18 | 24.73" | -2.10% | +80 mm | 58.7 mph | calculate → |
| 295/35R18 | 26.13" | +3.43% | +90 mm | 62.1 mph | calculate → |
| 205/40R18 | 24.46" | -3.19% | 0 mm | 58.1 mph | calculate → |
| 335/30R18 | 25.91" | +2.57% | +130 mm | 61.5 mph | calculate → |
| 215/50R18 | 26.46" | +4.75% | +10 mm | 62.9 mph | calculate → |
| 225/35R18 | 24.20" | -4.21% | +20 mm | 57.5 mph | calculate → |
| 305/35R18 | 26.41" | +4.52% | +100 mm | 62.7 mph | calculate → |
| 235/35R18 | 24.48" | -3.12% | +30 mm | 58.1 mph | calculate → |
| 155/60R18 | 25.32" | +0.23% | -50 mm | 60.1 mph | calculate → |
| 305/30R18 | 25.20" | -0.23% | +100 mm | 59.9 mph | calculate → |
| 145/70R18 | 25.99" | +2.88% | -60 mm | 61.7 mph | calculate → |
| 26x12.00R18 | 26.00" | +2.91% | +100 mm | 61.7 mph | calculate → |
| 26x6.00R18 | 26.00" | +2.91% | -53 mm | 61.7 mph | calculate → |
| 26x8.00R18 | 26.00" | +2.91% | -2 mm | 61.7 mph | calculate → |
| 345/30R18 | 26.15" | +3.51% | +140 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 | |
|---|---|---|---|---|---|
| 205/50R17 common | 25.07" | -0.76% | 0 mm | 59.5 mph | calculate → |
| 215/50R17 common | 25.46" | +0.79% | +10 mm | 60.5 mph | calculate → |
| 235/45R17 common | 25.33" | +0.25% | +30 mm | 60.1 mph | calculate → |
| 235/35R19 common | 25.48" | +0.84% | +30 mm | 60.5 mph | calculate → |
| 255/40R17 common | 25.03" | -0.92% | +50 mm | 59.4 mph | calculate → |
| 225/35R19 | 25.20" | -0.25% | +20 mm | 59.9 mph | calculate → |
| 255/30R19 | 25.02" | -0.95% | +50 mm | 59.4 mph | calculate → |
| 275/30R19 | 25.50" | +0.92% | +70 mm | 60.6 mph | calculate → |
| 265/30R19 | 25.26" | -0.02% | +60 mm | 60.0 mph | calculate → |
| 265/40R17 | 25.35" | +0.33% | +60 mm | 60.2 mph | calculate → |
| 315/25R19 | 25.20" | -0.25% | +110 mm | 59.9 mph | calculate → |
| 295/35R17 | 25.13" | -0.53% | +90 mm | 59.7 mph | calculate → |
Try another size against 205/45R18
Questions
What size is 205/45R18 in inches?
205/45R18 is about 25.3" tall and 8.1" wide on a 18-inch rim — roughly a 25.5x8.00R18 in inch sizing.
What does 205/45R18 mean?
205 mm section width, sidewall 45% of the width (3.63"), radial construction, 18-inch rim.
What tire sizes are equivalent to 205/45R18?
On the same 18" rim, within 3% of the diameter: 265/35R18 (+0.16%), 155/60R18 (+0.23%), 305/30R18 (-0.23%), 235/40R18 (+0.55%), 225/40R18 (-0.70%), 315/30R18 (+0.70%).
How many revolutions per mile does a 205/45R18 tire make?
About 798 revolutions per mile (circumference 79.4").
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.