305/45R18 tire size
305/45R18 is a metric size: 28.8" tall, 12.0" wide, on a 18" rim — about a 29x12.00R18. The sidewall is 5.4" and the tire turns 700 times per mile.
305/45R18 specs
| Overall diameter (height) | 28.81" · 732 mm |
|---|---|
| Section width | 12.01" · 305 mm |
| Sidewall height | 5.40" · 137 mm (45% of width) |
| Rim diameter | 18" |
| Circumference | 90.50" · 2.299 m |
| Revolutions per mile | 700 (435 per km) |
| Inch (flotation) equivalent | 29x12.00R18 |
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" | +1.03% | -70 mm | 60.6 mph | calculate → |
| 235/55R18 common | 28.18" | -2.19% | -70 mm | 58.7 mph | calculate → |
| 225/60R18 common | 28.63" | -0.62% | -80 mm | 59.6 mph | calculate → |
| 245/60R18 common | 29.57" | +2.67% | -60 mm | 61.6 mph | calculate → |
| 225/55R18 common | 27.74" | -3.69% | -80 mm | 57.8 mph | calculate → |
| 255/55R18 common | 29.04" | +0.82% | -50 mm | 60.5 mph | calculate → |
| 235/65R18 common | 30.03" | +4.24% | -70 mm | 62.5 mph | calculate → |
| 245/50R18 common | 27.65" | -4.03% | -60 mm | 57.6 mph | calculate → |
| 255/60R18 | 30.05" | +4.31% | -50 mm | 62.6 mph | calculate → |
| 245/55R18 | 28.61" | -0.68% | -60 mm | 59.6 mph | calculate → |
| 275/45R18 | 27.74" | -3.69% | -30 mm | 57.8 mph | calculate → |
| 265/45R18 | 27.39" | -4.92% | -40 mm | 57.0 mph | calculate → |
| 345/35R18 | 27.51" | -4.51% | +40 mm | 57.3 mph | calculate → |
| 295/45R18 | 28.45" | -1.23% | -10 mm | 59.3 mph | calculate → |
| 255/50R18 | 28.04" | -2.67% | -50 mm | 58.4 mph | calculate → |
| 155/90R18 | 28.98" | +0.62% | -150 mm | 60.4 mph | calculate → |
| 315/40R18 | 27.92" | -3.08% | +10 mm | 58.2 mph | calculate → |
| 285/50R18 | 29.22" | +1.44% | -20 mm | 60.9 mph | calculate → |
| 155/85R18 | 28.37" | -1.50% | -150 mm | 59.1 mph | calculate → |
| 215/60R18 | 28.16" | -2.26% | -90 mm | 58.6 mph | calculate → |
| 165/90R18 | 29.69" | +3.08% | -140 mm | 61.8 mph | calculate → |
| 305/40R18 | 27.61" | -4.17% | 0 mm | 57.5 mph | calculate → |
| 325/45R18 | 29.52" | +2.46% | +20 mm | 61.5 mph | calculate → |
| 285/45R18 | 28.10" | -2.46% | -20 mm | 58.5 mph | calculate → |
| 28x12.00R18 | 28.00" | -2.80% | 0 mm | 58.3 mph | calculate → |
| 145/85R18 | 27.70" | -3.83% | -160 mm | 57.7 mph | calculate → |
| 275/55R18 | 29.91" | +3.83% | -30 mm | 62.3 mph | calculate → |
| 265/50R18 | 28.43" | -1.30% | -40 mm | 59.2 mph | calculate → |
| 265/55R18 | 29.48" | +2.32% | -40 mm | 61.4 mph | calculate → |
| 225/65R18 | 29.52" | +2.46% | -80 mm | 61.5 mph | calculate → |
| 28x10.00R18 | 28.00" | -2.80% | -51 mm | 58.3 mph | calculate → |
| 205/60R18 | 27.69" | -3.90% | -100 mm | 57.7 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 | |
|---|---|---|---|---|---|
| 235/65R17 common | 29.03" | +0.77% | -70 mm | 60.5 mph | calculate → |
| 255/50R19 common | 29.04" | +0.81% | -50 mm | 60.5 mph | calculate → |
| 225/55R19 common | 28.74" | -0.22% | -80 mm | 59.9 mph | calculate → |
| 245/50R19 common | 28.65" | -0.56% | -60 mm | 59.7 mph | calculate → |
| 275/45R19 | 28.74" | -0.22% | -30 mm | 59.9 mph | calculate → |
| 255/60R17 | 29.05" | +0.83% | -50 mm | 60.5 mph | calculate → |
| 275/55R17 | 28.91" | +0.36% | -30 mm | 60.2 mph | calculate → |
| 215/70R17 | 28.85" | +0.15% | -90 mm | 60.1 mph | calculate → |
| 165/90R17 | 28.69" | -0.40% | -140 mm | 59.8 mph | calculate → |
| 155/80R19 | 28.76" | -0.15% | -150 mm | 59.9 mph | calculate → |
| 315/40R19 | 28.92" | +0.40% | +10 mm | 60.2 mph | calculate → |
| 245/60R17 | 28.57" | -0.81% | -60 mm | 59.5 mph | calculate → |
Try another size against 305/45R18
Questions
What size is 305/45R18 in inches?
305/45R18 is about 28.8" tall and 12.0" wide on a 18-inch rim — roughly a 29x12.00R18 in inch sizing.
What does 305/45R18 mean?
305 mm section width, sidewall 45% of the width (5.40"), radial construction, 18-inch rim.
What tire sizes are equivalent to 305/45R18?
On the same 18" rim, within 3% of the diameter: 155/90R18 (+0.62%), 225/60R18 (-0.62%), 245/55R18 (-0.68%), 255/55R18 (+0.82%), 235/60R18 (+1.03%), 295/45R18 (-1.23%).
How many revolutions per mile does a 305/45R18 tire make?
About 700 revolutions per mile (circumference 90.5").
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.