305/55R18 tire size in inches
A 305/55R18 tire measures
31.2" tall × 12.0" wide
6.60" sidewall on a 18" wheel. 646 revolutions per mile.
305/55R18 means a tire 305 mm wide, with sidewalls 55% as tall as the tire is wide (168 mm), radial construction (R), for a 18 inch wheel.
305/55R18 specs
| Overall diameter (height) | 31.21 inches (793 mm) |
|---|---|
| Section width | 12.01 inches (305 mm) |
| Sidewall height | 6.60 inches (168 mm) |
| Wheel (rim) diameter | 18 inches |
| Circumference | 98.0 inches (2,490 mm) |
| Revolutions per mile | 646 |
| Revolutions per kilometer | 402 |
| Approximate rim width | 9.0" to 10.5" |
| In inches (flotation style) | 31.2x12.0R18 |
| Aspect ratio | 55% |
Calculated from the size. Real tires differ by brand, model and tread depth, typically by a few tenths of an inch.
Sizes that can replace 305/55R18 on a 18" wheel
These 18" sizes are within 3% of 305/55R18's overall diameter, the range most tire shops treat as interchangeable.
| Size | Diameter | Width | Difference | Real speed at 60 | |
|---|---|---|---|---|---|
| 335/50R18 | 31.19" | 13.19" | −0.1% | 60.0 mph | Compare |
| 225/75R18 | 31.29" | 8.86" | +0.3% | 60.2 mph | Compare |
| 255/65R18 | 31.05" | 10.04" | −0.5% | 59.7 mph | Compare |
| 275/60R18 | 30.99" | 10.83" | −0.7% | 59.6 mph | Compare |
| 285/60R18 | 31.46" | 11.22" | +0.8% | 60.5 mph | Compare |
| 235/70R18 | 30.95" | 9.25" | −0.8% | 59.5 mph | Compare |
| 245/70R18 | 31.50" | 9.65" | +0.9% | 60.6 mph | Compare |
| 265/65R18 | 31.56" | 10.43" | +1.1% | 60.7 mph | Compare |
| 325/50R18 | 30.80" | 12.80" | −1.3% | 59.2 mph | Compare |
| 295/55R18 | 30.78" | 11.61" | −1.4% | 59.2 mph | Compare |
| 315/55R18 | 31.64" | 12.40" | +1.4% | 60.8 mph | Compare |
| 215/75R18 | 30.70" | 8.46" | −1.6% | 59.0 mph | Compare |
Same height on other wheel sizes (plus and minus sizing)
| Size | Wheel | Diameter | Difference | |
|---|---|---|---|---|
| 305/30R24 | 24" | 31.20" | 0.0% | Compare |
| 285/50R20 | 20" | 31.22" | 0.0% | Compare |
| 345/45R19 | 19" | 31.22" | +0.1% | Compare |
| 335/35R22 | 22" | 31.23" | +0.1% | Compare |
| 325/40R21 | 21" | 31.24" | +0.1% | Compare |
| 355/40R20 | 20" | 31.18" | −0.1% | Compare |
| 235/55R21 | 21" | 31.18" | −0.1% | Compare |
| 275/75R15 | 15" | 31.24" | +0.1% | Compare |
| 235/50R22 | 22" | 31.25" | +0.1% | Compare |
| 315/45R20 | 20" | 31.16" | −0.2% | Compare |
| 275/70R16 | 16" | 31.16" | −0.2% | Compare |
| 295/40R22 | 22" | 31.29" | +0.3% | Compare |
One size up or down
- 295/55R18narrower: 30.8" × 11.6"
- 315/55R18wider: 31.6" × 12.4"
- 305/50R18lower profile: 30.0" × 12.0"
- 305/60R18taller sidewall: 32.4" × 12.0"
Compare 305/55R18 with another size
Questions
- How tall is a 305/55R18 tire?
- A 305/55R18 tire is 31.2 inches tall (793 mm), calculated from the size. It is 12.0 inches wide with 6.6 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
- What does 305/55R18 mean?
- 305/55R18 means a tire 305 mm wide, with sidewalls 55% as tall as the tire is wide (168 mm), radial construction (R), for a 18 inch wheel.
- How many revolutions per mile does a 305/55R18 tire make?
- About 646 revolutions per mile, based on a circumference of 98.0 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
- What rim width fits a 305/55R18 tire?
- Roughly 9.0" to 10.5". Check the tire maker's approved rim range for the exact model before buying wheels.
- Can I use 335/50R18 instead of 305/55R18?
- 335/50R18 is −0.02 inches (−0.1%) in overall diameter, so at an indicated 60 mph you would be doing 60.0 mph. Differences under 3% are usually fine, but check clearance, load index and your vehicle's placard.