255/40R20 tire size
255/40R20 is a metric size: 28.0" tall, 10.0" wide, on a 20" rim — about a 28x10.00R20. The sidewall is 4.0" and the tire turns 719 times per mile.
255/40R20 specs
| Overall diameter (height) | 28.03" · 712 mm |
|---|---|
| Section width | 10.04" · 255 mm |
| Sidewall height | 4.02" · 102 mm (40% of width) |
| Rim diameter | 20" |
| Circumference | 88.06" · 2.237 m |
| Revolutions per mile | 719 (447 per km) |
| Inch (flotation) equivalent | 28x10.00R20 |
Equivalent sizes on a 20" 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 | |
|---|---|---|---|---|---|
| 245/45R20 common | 28.68" | +2.32% | -10 mm | 61.4 mph | compare → |
| 255/45R20 common | 29.04" | +3.58% | 0 mm | 62.1 mph | compare → |
| 275/40R20 common | 28.66" | +2.25% | +20 mm | 61.3 mph | compare → |
| 245/40R20 common | 27.72" | -1.12% | -10 mm | 59.3 mph | compare → |
| 245/35R20 common | 26.75" | -4.56% | -10 mm | 57.3 mph | compare → |
| 255/35R20 common | 27.03" | -3.58% | 0 mm | 57.9 mph | compare → |
| 275/35R20 common | 27.58" | -1.62% | +20 mm | 59.0 mph | compare → |
| 265/45R20 common | 29.39" | +4.85% | +10 mm | 62.9 mph | compare → |
| 285/35R20 common | 27.85" | -0.63% | +30 mm | 59.6 mph | compare → |
| 315/35R20 common | 28.68" | +2.32% | +60 mm | 61.4 mph | compare → |
| 285/30R20 common | 26.73" | -4.63% | +30 mm | 57.2 mph | compare → |
| 265/35R20 common | 27.30" | -2.60% | +10 mm | 58.4 mph | compare → |
| 295/30R20 | 26.97" | -3.79% | +40 mm | 57.7 mph | compare → |
| 305/30R20 | 27.20" | -2.95% | +50 mm | 58.2 mph | compare → |
| 295/40R20 | 29.29" | +4.49% | +40 mm | 62.7 mph | compare → |
| 295/35R20 | 28.13" | +0.35% | +40 mm | 60.2 mph | compare → |
| 305/35R20 | 28.41" | +1.33% | +50 mm | 60.8 mph | compare → |
| 285/40R20 | 28.98" | +3.37% | +30 mm | 62.0 mph | compare → |
| 235/50R20 | 29.25" | +4.35% | -20 mm | 62.6 mph | compare → |
| 235/45R20 | 28.33" | +1.05% | -20 mm | 60.6 mph | compare → |
| 265/40R20 | 28.35" | +1.12% | +10 mm | 60.7 mph | compare → |
| 315/30R20 | 27.44" | -2.11% | +60 mm | 58.7 mph | compare → |
| 235/40R20 | 27.40" | -2.25% | -20 mm | 58.7 mph | calculate → |
| 335/30R20 | 27.91" | -0.42% | +80 mm | 59.7 mph | calculate → |
| 325/30R20 | 27.68" | -1.26% | +70 mm | 59.2 mph | calculate → |
| 345/30R20 | 28.15" | +0.42% | +90 mm | 60.3 mph | calculate → |
| 215/45R20 | 27.62" | -1.47% | -40 mm | 59.1 mph | calculate → |
| 345/25R20 | 26.79" | -4.42% | +90 mm | 57.3 mph | calculate → |
| 195/50R20 | 27.68" | -1.26% | -60 mm | 59.2 mph | calculate → |
| 325/35R20 | 28.96" | +3.30% | +70 mm | 62.0 mph | calculate → |
| 225/40R20 | 27.09" | -3.37% | -30 mm | 58.0 mph | calculate → |
| 175/55R20 | 27.58" | -1.62% | -80 mm | 59.0 mph | calculate → |
| 145/65R20 | 27.42" | -2.18% | -110 mm | 58.7 mph | calculate → |
| 155/60R20 | 27.32" | -2.53% | -100 mm | 58.5 mph | calculate → |
| 29x15.00R20 | 29.00" | +3.46% | +126 mm | 62.1 mph | calculate → |
| 29x18.00R20 | 29.00" | +3.46% | +202 mm | 62.1 mph | calculate → |
| 145/60R20 | 26.85" | -4.21% | -110 mm | 57.5 mph | calculate → |
| 225/45R20 | 27.97" | -0.21% | -30 mm | 59.9 mph | calculate → |
| 155/65R20 | 27.93" | -0.35% | -100 mm | 59.8 mph | calculate → |
| 165/60R20 | 27.80" | -0.84% | -90 mm | 59.5 mph | calculate → |
| 195/55R20 | 28.44" | +1.47% | -60 mm | 60.9 mph | calculate → |
Plus / minus sizing: 19" and 21" rims
Same overall height on a different rim. Check wheel width and clearance before switching.
| Size | Diameter | Difference | Width | Speedo at 60 | |
|---|---|---|---|---|---|
| 255/45R19 common | 28.04" | +0.01% | 0 mm | 60.0 mph | compare → |
| 235/50R19 common | 28.25" | +0.79% | -20 mm | 60.5 mph | compare → |
| 265/35R21 | 28.30" | +0.97% | +10 mm | 60.6 mph | compare → |
| 245/35R21 | 27.75" | -1.00% | -10 mm | 59.4 mph | compare → |
| 285/40R19 | 27.98" | -0.20% | +30 mm | 59.9 mph | compare → |
| 255/35R21 | 28.03" | -0.01% | 0 mm | 60.0 mph | compare → |
| 295/30R21 | 27.97" | -0.22% | +40 mm | 59.9 mph | compare → |
| 305/30R21 | 28.20" | +0.62% | +50 mm | 60.4 mph | compare → |
| 295/40R19 | 28.29" | +0.93% | +40 mm | 60.6 mph | compare → |
| 355/25R21 | 27.99" | -0.15% | +100 mm | 59.9 mph | calculate → |
| 345/25R21 | 27.79" | -0.86% | +90 mm | 59.5 mph | calculate → |
| 145/80R19 | 28.13" | +0.37% | -110 mm | 60.2 mph | calculate → |
| 225/50R19 | 27.86" | -0.62% | -30 mm | 59.6 mph | calculate → |
Try another size against 255/40R20
Questions
What size is 255/40R20 in inches?
255/40R20 is about 28.0" tall and 10.0" wide on a 20-inch rim — roughly a 28x10.00R20 in inch sizing.
What does 255/40R20 mean?
255 mm section width, sidewall 40% of the width (4.02"), radial construction, 20-inch rim.
What tire sizes are equivalent to 255/40R20?
On the same 20" rim, within 3% of the diameter: 225/45R20 (-0.21%), 155/65R20 (-0.35%), 295/35R20 (+0.35%), 335/30R20 (-0.42%), 345/30R20 (+0.42%), 285/35R20 (-0.63%).
How many revolutions per mile does a 255/40R20 tire make?
About 719 revolutions per mile (circumference 88.1").
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.