285/30R21 tire size
285/30R21 is a metric size: 27.7" tall, 11.2" wide, on a 21" rim — about a 27.5x11.00R21. The sidewall is 3.4" and the tire turns 727 times per mile.
285/30R21 specs
| Overall diameter (height) | 27.73" · 704 mm |
|---|---|
| Section width | 11.22" · 285 mm |
| Sidewall height | 3.37" · 86 mm (30% of width) |
| Rim diameter | 21" |
| Circumference | 87.12" · 2.213 m |
| Revolutions per mile | 727 (452 per km) |
| Inch (flotation) equivalent | 27.5x11.00R21 |
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 | |
|---|---|---|---|---|---|
| 275/35R21 common | 28.58" | +3.05% | -10 mm | 61.8 mph | compare → |
| 255/40R21 | 29.03" | +4.68% | -30 mm | 62.8 mph | compare → |
| 265/35R21 | 28.30" | +2.06% | -20 mm | 61.2 mph | compare → |
| 245/35R21 | 27.75" | +0.07% | -40 mm | 60.0 mph | compare → |
| 325/30R21 | 28.68" | +3.41% | +40 mm | 62.0 mph | compare → |
| 255/35R21 | 28.03" | +1.06% | -30 mm | 60.6 mph | compare → |
| 315/30R21 | 28.44" | +2.56% | +30 mm | 61.5 mph | compare → |
| 285/35R21 | 28.85" | +4.05% | 0 mm | 62.4 mph | compare → |
| 245/40R21 | 28.72" | +3.55% | -40 mm | 62.1 mph | compare → |
| 295/30R21 | 27.97" | +0.85% | +10 mm | 60.5 mph | compare → |
| 305/30R21 | 28.20" | +1.70% | +20 mm | 61.0 mph | compare → |
| 275/30R21 | 27.50" | -0.85% | -10 mm | 59.5 mph | compare → |
| 255/30R21 | 27.02" | -2.56% | -30 mm | 58.5 mph | calculate → |
| 355/25R21 | 27.99" | +0.92% | +70 mm | 60.6 mph | calculate → |
| 295/25R21 | 26.81" | -3.34% | +10 mm | 58.0 mph | calculate → |
| 335/30R21 | 28.91" | +4.26% | +50 mm | 62.6 mph | calculate → |
| 265/30R21 | 27.26" | -1.70% | -20 mm | 59.0 mph | calculate → |
| 345/25R21 | 27.79" | +0.21% | +60 mm | 60.1 mph | calculate → |
| 325/25R21 | 27.40" | -1.21% | +40 mm | 59.3 mph | calculate → |
| 305/25R21 | 27.00" | -2.63% | +20 mm | 58.4 mph | calculate → |
| 225/45R21 | 28.97" | +4.47% | -60 mm | 62.7 mph | calculate → |
| 245/30R21 | 26.79" | -3.41% | -40 mm | 58.0 mph | calculate → |
| 275/25R21 | 26.41" | -4.76% | -10 mm | 57.1 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 | |
|---|---|---|---|---|---|
| 245/40R20 common | 27.72" | -0.06% | -40 mm | 60.0 mph | compare → |
| 275/35R20 common | 27.58" | -0.55% | -10 mm | 59.7 mph | compare → |
| 285/35R20 common | 27.85" | +0.44% | 0 mm | 60.3 mph | compare → |
| 295/25R22 | 27.81" | +0.27% | +10 mm | 60.2 mph | compare → |
| 335/30R20 | 27.91" | +0.65% | +50 mm | 60.4 mph | calculate → |
| 325/30R20 | 27.68" | -0.20% | +40 mm | 59.9 mph | calculate → |
| 245/30R22 | 27.79" | +0.20% | -40 mm | 60.1 mph | calculate → |
| 215/45R20 | 27.62" | -0.41% | -70 mm | 59.8 mph | calculate → |
| 235/30R22 | 27.55" | -0.65% | -50 mm | 59.6 mph | calculate → |
| 195/50R20 | 27.68" | -0.20% | -90 mm | 59.9 mph | calculate → |
| 285/25R22 | 27.61" | -0.44% | 0 mm | 59.7 mph | calculate → |
| 175/55R20 | 27.58" | -0.55% | -110 mm | 59.7 mph | calculate → |
| 305/25R22 | 28.00" | +0.98% | +20 mm | 60.6 mph | calculate → |
| 165/60R20 | 27.80" | +0.23% | -120 mm | 60.1 mph | calculate → |
| 155/65R20 | 27.93" | +0.72% | -130 mm | 60.4 mph | calculate → |
| 225/45R20 | 27.97" | +0.87% | -60 mm | 60.5 mph | calculate → |
Try another size against 285/30R21
Questions
What size is 285/30R21 in inches?
285/30R21 is about 27.7" tall and 11.2" wide on a 21-inch rim — roughly a 27.5x11.00R21 in inch sizing.
What does 285/30R21 mean?
285 mm section width, sidewall 30% of the width (3.37"), radial construction, 21-inch rim.
What tire sizes are equivalent to 285/30R21?
On the same 21" rim, within 3% of the diameter: 245/35R21 (+0.07%), 345/25R21 (+0.21%), 275/30R21 (-0.85%), 295/30R21 (+0.85%), 355/25R21 (+0.92%), 255/35R21 (+1.06%).
How many revolutions per mile does a 285/30R21 tire make?
About 727 revolutions per mile (circumference 87.1").
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.