215/40R18 tire size
215/40R18 is a metric size: 24.8" tall, 8.5" wide, on a 18" rim — about a 25x8.50R18. The sidewall is 3.4" and the tire turns 814 times per mile.
215/40R18 specs
| Overall diameter (height) | 24.77" · 629 mm |
|---|---|
| Section width | 8.46" · 215 mm |
| Sidewall height | 3.39" · 86 mm (40% of width) |
| Rim diameter | 18" |
| Circumference | 77.82" · 1.977 m |
| Revolutions per mile | 814 (506 per km) |
| Inch (flotation) equivalent | 25x8.50R18 |
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" | +3.81% | +30 mm | 62.3 mph | compare → |
| 225/45R18 common | 25.97" | +4.85% | +10 mm | 62.9 mph | compare → |
| 225/40R18 common | 25.09" | +1.27% | +10 mm | 60.8 mph | compare → |
| 235/40R18 common | 25.40" | +2.54% | +20 mm | 61.5 mph | compare → |
| 255/35R18 common | 25.03" | +1.03% | +40 mm | 60.6 mph | compare → |
| 275/35R18 common | 25.58" | +3.26% | +60 mm | 62.0 mph | compare → |
| 265/35R18 common | 25.30" | +2.15% | +50 mm | 61.3 mph | compare → |
| 215/45R18 common | 25.62" | +3.42% | 0 mm | 62.1 mph | compare → |
| 245/35R18 common | 24.75" | -0.08% | +30 mm | 60.0 mph | compare → |
| 285/35R18 | 25.85" | +4.37% | +70 mm | 62.6 mph | compare → |
| 295/30R18 | 24.97" | +0.79% | +80 mm | 60.5 mph | compare → |
| 285/30R18 | 24.73" | -0.16% | +70 mm | 59.9 mph | compare → |
| 315/30R18 | 25.44" | +2.70% | +100 mm | 61.6 mph | compare → |
| 205/40R18 | 24.46" | -1.27% | -10 mm | 59.2 mph | compare → |
| 335/30R18 | 25.91" | +4.61% | +120 mm | 62.8 mph | compare → |
| 225/35R18 | 24.20" | -2.30% | +10 mm | 58.6 mph | calculate → |
| 215/35R18 | 23.93" | -3.42% | 0 mm | 57.9 mph | calculate → |
| 235/35R18 | 24.48" | -1.19% | +20 mm | 59.3 mph | calculate → |
| 305/30R18 | 25.20" | +1.75% | +90 mm | 61.0 mph | calculate → |
| 155/60R18 | 25.32" | +2.23% | -60 mm | 61.3 mph | calculate → |
| 205/35R18 | 23.65" | -4.53% | -10 mm | 57.3 mph | calculate → |
| 145/70R18 | 25.99" | +4.93% | -70 mm | 63.0 mph | calculate → |
| 235/30R18 | 23.55" | -4.93% | +20 mm | 57.0 mph | calculate → |
| 26x12.00R18 | 26.00" | +4.96% | +90 mm | 63.0 mph | calculate → |
| 26x6.00R18 | 26.00" | +4.96% | -63 mm | 63.0 mph | calculate → |
| 26x8.00R18 | 26.00" | +4.96% | -12 mm | 63.0 mph | calculate → |
| 205/45R18 | 25.26" | +1.99% | -10 mm | 61.2 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 | |
|---|---|---|---|---|---|
| 225/45R17 common | 24.97" | +0.81% | +10 mm | 60.5 mph | compare → |
| 215/45R17 common | 24.62" | -0.62% | 0 mm | 59.6 mph | compare → |
| 245/40R17 common | 24.72" | -0.22% | +30 mm | 59.9 mph | compare → |
| 275/35R17 | 24.58" | -0.78% | +60 mm | 59.5 mph | calculate → |
| 245/30R19 | 24.79" | +0.06% | +30 mm | 60.0 mph | calculate → |
| 295/25R19 | 24.81" | +0.14% | +80 mm | 60.1 mph | calculate → |
| 215/35R19 | 24.93" | +0.62% | 0 mm | 60.4 mph | calculate → |
| 145/70R17 | 24.99" | +0.89% | -70 mm | 60.5 mph | calculate → |
| 235/30R19 | 24.55" | -0.89% | +20 mm | 59.5 mph | calculate → |
Try another size against 215/40R18
Questions
What size is 215/40R18 in inches?
215/40R18 is about 24.8" tall and 8.5" wide on a 18-inch rim — roughly a 25x8.50R18 in inch sizing.
What does 215/40R18 mean?
215 mm section width, sidewall 40% of the width (3.39"), radial construction, 18-inch rim.
What tire sizes are equivalent to 215/40R18?
On the same 18" rim, within 3% of the diameter: 245/35R18 (-0.08%), 285/30R18 (-0.16%), 295/30R18 (+0.79%), 255/35R18 (+1.03%), 235/35R18 (-1.19%), 225/40R18 (+1.27%).
How many revolutions per mile does a 215/40R18 tire make?
About 814 revolutions per mile (circumference 77.8").
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.