205/40R18 tire size in inches
A 205/40R18 tire measures
24.5" tall × 8.1" wide
3.23" sidewall on a 18" wheel. 825 revolutions per mile.
205/40R18 means a tire 205 mm wide, with sidewalls 40% as tall as the tire is wide (82 mm), radial construction (R), for a 18 inch wheel.
205/40R18 specs
| Overall diameter (height) | 24.46 inches (621 mm) |
|---|---|
| Section width | 8.07 inches (205 mm) |
| Sidewall height | 3.23 inches (82 mm) |
| Wheel (rim) diameter | 18 inches |
| Circumference | 76.8 inches (1,952 mm) |
| Revolutions per mile | 825 |
| Revolutions per kilometer | 512 |
| Approximate rim width | 6.5" to 8.0" |
| In inches (flotation style) | 24.5x8.1R18 |
| 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 205/40R18 on a 18" wheel
These 18" sizes are within 3% of 205/40R18's overall diameter, the range most tire shops treat as interchangeable.
| Size | Diameter | Width | Difference | Real speed at 60 | |
|---|---|---|---|---|---|
| 235/35R18 | 24.48" | 9.25" | +0.1% | 60.0 mph | Compare |
| 225/35R18 | 24.20" | 8.86" | −1.0% | 59.4 mph | Compare |
| 245/35R18 | 24.75" | 9.65" | +1.2% | 60.7 mph | Compare |
| 195/40R18 | 24.14" | 7.68" | −1.3% | 59.2 mph | Compare |
| 215/40R18 | 24.77" | 8.46" | +1.3% | 60.8 mph | Compare |
| 195/45R18 | 24.91" | 7.68" | +1.9% | 61.1 mph | Compare |
| 215/35R18 | 23.93" | 8.46" | −2.2% | 58.7 mph | Compare |
| 255/35R18 | 25.03" | 10.04" | +2.3% | 61.4 mph | Compare |
| 225/40R18 | 25.09" | 8.86" | +2.6% | 61.5 mph | Compare |
Same height on other wheel sizes (plus and minus sizing)
| Size | Wheel | Diameter | Difference | |
|---|---|---|---|---|
| 215/50R16 | 16" | 24.46" | 0.0% | Compare |
| 185/65R15 | 15" | 24.47" | 0.0% | Compare |
| 195/55R16 | 16" | 24.44" | 0.0% | Compare |
| 225/25R20 | 20" | 24.43" | −0.1% | Compare |
| 205/65R14 | 14" | 24.49" | +0.1% | Compare |
| 275/25R19 | 19" | 24.41" | −0.2% | Compare |
| 235/40R17 | 17" | 24.40" | −0.2% | Compare |
| 195/75R13 | 13" | 24.52" | +0.2% | Compare |
| 225/65R13 | 13" | 24.52" | +0.2% | Compare |
| 165/80R14 | 14" | 24.39" | −0.3% | Compare |
| 265/45R15 | 15" | 24.39" | −0.3% | Compare |
| 155/85R14 | 14" | 24.37" | −0.3% | Compare |
One size up or down
- 195/40R18narrower: 24.1" × 7.7"
- 215/40R18wider: 24.8" × 8.5"
- 205/35R18lower profile: 23.6" × 8.1"
- 205/45R18taller sidewall: 25.3" × 8.1"
Compare 205/40R18 with another size
Questions
- How tall is a 205/40R18 tire?
- A 205/40R18 tire is 24.5 inches tall (621 mm), calculated from the size. It is 8.1 inches wide with 3.2 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
- What does 205/40R18 mean?
- 205/40R18 means a tire 205 mm wide, with sidewalls 40% as tall as the tire is wide (82 mm), radial construction (R), for a 18 inch wheel.
- How many revolutions per mile does a 205/40R18 tire make?
- About 825 revolutions per mile, based on a circumference of 76.8 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
- What rim width fits a 205/40R18 tire?
- Roughly 6.5" to 8.0". Check the tire maker's approved rim range for the exact model before buying wheels.
- Can I use 235/35R18 instead of 205/40R18?
- 235/35R18 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.