255/40R18 tire size
255/40R18 is a metric size: 26.0" tall, 10.0" wide, on a 18" rim — about a 26x10.00R18. The sidewall is 4.0" and the tire turns 775 times per mile.
255/40R18 specs
| Overall diameter (height) | 26.03" · 661 mm |
|---|---|
| Section width | 10.04" · 255 mm |
| Sidewall height | 4.02" · 102 mm (40% of width) |
| Rim diameter | 18" |
| Circumference | 81.78" · 2.077 m |
| Revolutions per mile | 775 (481 per km) |
| Inch (flotation) equivalent | 26x10.00R18 |
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 | |
|---|---|---|---|---|---|
| 225/45R18 common | 25.97" | -0.23% | -30 mm | 59.9 mph | compare → |
| 245/40R18 common | 25.72" | -1.21% | -10 mm | 59.3 mph | compare → |
| 225/40R18 common | 25.09" | -3.63% | -30 mm | 57.8 mph | compare → |
| 245/45R18 common | 26.68" | +2.50% | -10 mm | 61.5 mph | compare → |
| 235/50R18 common | 27.25" | +4.69% | -20 mm | 62.8 mph | compare → |
| 235/45R18 common | 26.33" | +1.13% | -20 mm | 60.7 mph | compare → |
| 235/40R18 common | 25.40" | -2.42% | -20 mm | 58.5 mph | compare → |
| 225/50R18 common | 26.86" | +3.18% | -30 mm | 61.9 mph | compare → |
| 255/35R18 common | 25.03" | -3.86% | 0 mm | 57.7 mph | compare → |
| 275/35R18 common | 25.58" | -1.74% | +20 mm | 59.0 mph | compare → |
| 265/35R18 common | 25.30" | -2.80% | +10 mm | 58.3 mph | compare → |
| 255/45R18 common | 27.04" | +3.86% | 0 mm | 62.3 mph | compare → |
| 215/55R18 common | 27.31" | +4.92% | -40 mm | 62.9 mph | compare → |
| 275/40R18 common | 26.66" | +2.42% | +20 mm | 61.5 mph | compare → |
| 215/45R18 common | 25.62" | -1.59% | -40 mm | 59.0 mph | compare → |
| 245/35R18 common | 24.75" | -4.92% | -10 mm | 57.1 mph | compare → |
| 215/40R18 | 24.77" | -4.84% | -40 mm | 57.1 mph | compare → |
| 285/35R18 | 25.85" | -0.68% | +30 mm | 59.6 mph | compare → |
| 265/40R18 | 26.35" | +1.21% | +10 mm | 60.7 mph | compare → |
| 295/30R18 | 24.97" | -4.08% | +40 mm | 57.5 mph | compare → |
| 315/30R18 | 25.44" | -2.27% | +60 mm | 58.6 mph | compare → |
| 285/30R18 | 24.73" | -4.99% | +30 mm | 57.0 mph | compare → |
| 295/35R18 | 26.13" | +0.38% | +40 mm | 60.2 mph | compare → |
| 335/30R18 | 25.91" | -0.45% | +80 mm | 59.7 mph | compare → |
| 215/50R18 | 26.46" | +1.66% | -40 mm | 61.0 mph | compare → |
| 295/40R18 | 27.29" | +4.84% | +40 mm | 62.9 mph | compare → |
| 285/40R18 | 26.98" | +3.63% | +30 mm | 62.2 mph | calculate → |
| 305/35R18 | 26.41" | +1.44% | +50 mm | 60.9 mph | calculate → |
| 26x12.00R18 | 26.00" | -0.12% | +50 mm | 59.9 mph | calculate → |
| 26x6.00R18 | 26.00" | -0.12% | -103 mm | 59.9 mph | calculate → |
| 26x8.00R18 | 26.00" | -0.12% | -52 mm | 59.9 mph | calculate → |
| 145/70R18 | 25.99" | -0.15% | -110 mm | 59.9 mph | calculate → |
| 155/70R18 | 26.54" | +1.97% | -100 mm | 61.2 mph | calculate → |
| 155/60R18 | 25.32" | -2.72% | -100 mm | 58.4 mph | calculate → |
| 305/30R18 | 25.20" | -3.18% | +50 mm | 58.1 mph | calculate → |
| 325/35R18 | 26.96" | +3.55% | +70 mm | 62.1 mph | calculate → |
| 165/70R18 | 27.09" | +4.08% | -90 mm | 62.5 mph | calculate → |
| 145/80R18 | 27.13" | +4.23% | -110 mm | 62.5 mph | calculate → |
| 345/30R18 | 26.15" | +0.45% | +90 mm | 60.3 mph | calculate → |
| 315/35R18 | 26.68" | +2.50% | +60 mm | 61.5 mph | calculate → |
| 205/45R18 | 25.26" | -2.95% | -50 mm | 58.2 mph | calculate → |
| 195/60R18 | 27.21" | +4.54% | -60 mm | 62.7 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 | |
|---|---|---|---|---|---|
| 225/50R17 common | 25.86" | -0.67% | -30 mm | 59.6 mph | compare → |
| 255/35R19 common | 26.03" | -0.02% | 0 mm | 60.0 mph | compare → |
| 225/40R19 common | 26.09" | +0.21% | -30 mm | 60.1 mph | compare → |
| 235/50R17 common | 26.25" | +0.85% | -20 mm | 60.5 mph | compare → |
| 205/55R17 | 25.88" | -0.59% | -50 mm | 59.6 mph | compare → |
| 305/30R19 | 26.20" | +0.67% | +50 mm | 60.4 mph | compare → |
| 295/30R19 | 25.97" | -0.24% | +40 mm | 59.9 mph | compare → |
| 255/45R17 | 26.04" | +0.02% | 0 mm | 60.0 mph | compare → |
| 335/35R17 | 26.23" | +0.77% | +80 mm | 60.5 mph | calculate → |
| 285/40R17 | 25.98" | -0.21% | +30 mm | 59.9 mph | calculate → |
| 195/60R17 | 26.21" | +0.70% | -60 mm | 60.4 mph | calculate → |
| 175/65R17 | 25.96" | -0.29% | -80 mm | 59.8 mph | calculate → |
| 145/80R17 | 26.13" | +0.39% | -110 mm | 60.2 mph | calculate → |
| 26x6.00R17 | 26.00" | -0.12% | -103 mm | 59.9 mph | calculate → |
| 165/70R17 | 26.09" | +0.24% | -90 mm | 60.1 mph | calculate → |
| 295/40R17 | 26.29" | +1.00% | +40 mm | 60.6 mph | calculate → |
Try another size against 255/40R18
Questions
What size is 255/40R18 in inches?
255/40R18 is about 26.0" tall and 10.0" wide on a 18-inch rim — roughly a 26x10.00R18 in inch sizing.
What does 255/40R18 mean?
255 mm section width, sidewall 40% of the width (4.02"), radial construction, 18-inch rim.
What tire sizes are equivalent to 255/40R18?
On the same 18" rim, within 3% of the diameter: 26x12.00R18 (-0.12%), 26x6.00R18 (-0.12%), 26x8.00R18 (-0.12%), 145/70R18 (-0.15%), 225/45R18 (-0.23%), 295/35R18 (+0.38%).
How many revolutions per mile does a 255/40R18 tire make?
About 775 revolutions per mile (circumference 81.8").
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.