255/50R21 tire size
255/50R21 is a metric size: 31.0" tall, 10.0" wide, on a 21" rim — about a 31x10.00R21. The sidewall is 5.0" and the tire turns 650 times per mile.
255/50R21 specs
| Overall diameter (height) | 31.04" · 788 mm |
|---|---|
| Section width | 10.04" · 255 mm |
| Sidewall height | 5.02" · 127 mm (50% of width) |
| Rim diameter | 21" |
| Circumference | 97.51" · 2.477 m |
| Revolutions per mile | 650 (404 per km) |
| Inch (flotation) equivalent | 31x10.00R21 |
Equivalent sizes on a 21" 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 | |
|---|---|---|---|---|---|
| 275/45R21 | 30.74" | -0.95% | +20 mm | 59.4 mph | compare → |
| 285/45R21 | 31.10" | +0.19% | +30 mm | 60.1 mph | compare → |
| 295/40R21 | 30.29" | -2.41% | +40 mm | 58.6 mph | compare → |
| 265/45R21 | 30.39" | -2.09% | +10 mm | 58.7 mph | compare → |
| 285/40R21 | 29.98" | -3.42% | +30 mm | 57.9 mph | compare → |
| 275/40R21 | 29.66" | -4.44% | +20 mm | 57.3 mph | compare → |
| 315/35R21 | 29.68" | -4.38% | +60 mm | 57.4 mph | compare → |
| 315/40R21 | 30.92" | -0.38% | +60 mm | 59.8 mph | compare → |
| 255/45R21 | 30.04" | -3.23% | 0 mm | 58.1 mph | compare → |
| 245/45R21 | 29.68" | -4.38% | -10 mm | 57.4 mph | compare → |
| 275/50R21 | 31.83" | +2.54% | +20 mm | 61.5 mph | compare → |
| 235/50R21 | 30.25" | -2.54% | -20 mm | 58.5 mph | calculate → |
| 325/40R21 | 31.24" | +0.63% | +70 mm | 60.4 mph | calculate → |
| 305/40R21 | 30.61" | -1.40% | +50 mm | 59.2 mph | calculate → |
| 315/45R21 | 32.16" | +3.61% | +60 mm | 62.2 mph | calculate → |
Plus / minus sizing: 20" and 22" rims
Same overall height on a different rim. Check wheel width and clearance before switching.
| Size | Diameter | Difference | Width | Speedo at 60 | |
|---|---|---|---|---|---|
| 255/55R20 common | 31.04" | +0.01% | 0 mm | 60.0 mph | compare → |
| 275/50R20 common | 30.83" | -0.68% | +20 mm | 59.6 mph | compare → |
| 285/40R22 | 30.98" | -0.20% | +30 mm | 59.9 mph | compare → |
| 285/50R20 | 31.22" | +0.58% | +30 mm | 60.4 mph | compare → |
| 325/35R22 | 30.96" | -0.27% | +70 mm | 59.8 mph | compare → |
| 295/40R22 | 31.29" | +0.81% | +40 mm | 60.5 mph | compare → |
| 255/45R22 | 31.04" | -0.01% | 0 mm | 60.0 mph | calculate → |
| 235/60R20 | 31.10" | +0.20% | -20 mm | 60.1 mph | calculate → |
| 31x18.00R20 | 31.00" | -0.13% | +202 mm | 59.9 mph | calculate → |
| 305/45R20 | 30.81" | -0.75% | +50 mm | 59.6 mph | calculate → |
Try another size against 255/50R21
Questions
What size is 255/50R21 in inches?
255/50R21 is about 31.0" tall and 10.0" wide on a 21-inch rim — roughly a 31x10.00R21 in inch sizing.
What does 255/50R21 mean?
255 mm section width, sidewall 50% of the width (5.02"), radial construction, 21-inch rim.
What tire sizes are equivalent to 255/50R21?
On the same 21" rim, within 3% of the diameter: 285/45R21 (+0.19%), 315/40R21 (-0.38%), 325/40R21 (+0.63%), 275/45R21 (-0.95%), 305/40R21 (-1.40%), 265/45R21 (-2.09%).
How many revolutions per mile does a 255/50R21 tire make?
About 650 revolutions per mile (circumference 97.5").
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.