325/40R18 tire size in inches
A 325/40R18 tire measures
28.2" tall × 12.8" wide
5.12" sidewall on a 18" wheel. 714 revolutions per mile.
325/40R18 means a tire 325 mm wide, with sidewalls 40% as tall as the tire is wide (130 mm), radial construction (R), for a 18 inch wheel.
325/40R18 specs
| Overall diameter (height) | 28.24 inches (717 mm) |
|---|---|
| Section width | 12.80 inches (325 mm) |
| Sidewall height | 5.12 inches (130 mm) |
| Wheel (rim) diameter | 18 inches |
| Circumference | 88.7 inches (2,253 mm) |
| Revolutions per mile | 714 |
| Revolutions per kilometer | 444 |
| Approximate rim width | 10.5" to 12.0" |
| In inches (flotation style) | 28.2x12.8R18 |
| Aspect ratio | 40% |
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 325/40R18 on a 18" wheel
These 18" sizes are within 3% of 325/40R18's overall diameter, the range most tire shops treat as interchangeable.
| Size | Diameter | Width | Difference | Real speed at 60 | |
|---|---|---|---|---|---|
| 235/55R18 | 28.18" | 9.25" | −0.2% | 59.9 mph | Compare |
| 215/60R18 | 28.16" | 8.46" | −0.3% | 59.8 mph | Compare |
| 285/45R18 | 28.10" | 11.22" | −0.5% | 59.7 mph | Compare |
| 265/50R18 | 28.43" | 10.43" | +0.7% | 60.4 mph | Compare |
| 255/50R18 | 28.04" | 10.04" | −0.7% | 59.6 mph | Compare |
| 295/45R18 | 28.45" | 11.61" | +0.8% | 60.5 mph | Compare |
| 205/65R18 | 28.49" | 8.07" | +0.9% | 60.5 mph | Compare |
| 195/65R18 | 27.98" | 7.68" | −0.9% | 59.5 mph | Compare |
| 335/40R18 | 28.55" | 13.19" | +1.1% | 60.7 mph | Compare |
| 315/40R18 | 27.92" | 12.40" | −1.1% | 59.3 mph | Compare |
| 245/55R18 | 28.61" | 9.65" | +1.3% | 60.8 mph | Compare |
| 225/60R18 | 28.63" | 8.86" | +1.4% | 60.8 mph | Compare |
Same height on other wheel sizes (plus and minus sizing)
| Size | Wheel | Diameter | Difference | |
|---|---|---|---|---|
| 335/35R19 | 19" | 28.23" | 0.0% | Compare |
| 235/50R19 | 19" | 28.25" | +0.1% | Compare |
| 285/50R17 | 17" | 28.22" | −0.1% | Compare |
| 265/30R22 | 22" | 28.26" | +0.1% | Compare |
| 305/30R21 | 21" | 28.20" | −0.1% | Compare |
| 315/25R22 | 22" | 28.20" | −0.1% | Compare |
| 195/80R16 | 16" | 28.28" | +0.2% | Compare |
| 225/75R15 | 15" | 28.29" | +0.2% | Compare |
| 295/40R19 | 19" | 28.29" | +0.2% | Compare |
| 205/70R17 | 17" | 28.30" | +0.2% | Compare |
| 225/80R14 | 14" | 28.17" | −0.2% | Compare |
| 265/35R21 | 21" | 28.30" | +0.2% | Compare |
One size up or down
- 315/40R18narrower: 27.9" × 12.4"
- 335/40R18wider: 28.6" × 13.2"
- 325/35R18lower profile: 27.0" × 12.8"
- 325/45R18taller sidewall: 29.5" × 12.8"
Compare 325/40R18 with another size
Questions
- How tall is a 325/40R18 tire?
- A 325/40R18 tire is 28.2 inches tall (717 mm), calculated from the size. It is 12.8 inches wide with 5.1 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
- What does 325/40R18 mean?
- 325/40R18 means a tire 325 mm wide, with sidewalls 40% as tall as the tire is wide (130 mm), radial construction (R), for a 18 inch wheel.
- How many revolutions per mile does a 325/40R18 tire make?
- About 714 revolutions per mile, based on a circumference of 88.7 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
- What rim width fits a 325/40R18 tire?
- Roughly 10.5" to 12.0". Check the tire maker's approved rim range for the exact model before buying wheels.
- Can I use 235/55R18 instead of 325/40R18?
- 235/55R18 is −0.06 inches (−0.2%) in overall diameter, so at an indicated 60 mph you would be doing 59.9 mph. Differences under 3% are usually fine, but check clearance, load index and your vehicle's placard.