275/30R21 tire size
275/30R21 is a metric size: 27.5" tall, 10.8" wide, on a 21" rim — about a 27.5x11.00R21. The sidewall is 3.2" and the tire turns 733 times per mile.
275/30R21 specs
| Overall diameter (height) | 27.50" · 698 mm |
|---|---|
| Section width | 10.83" · 275 mm |
| Sidewall height | 3.25" · 83 mm (30% of width) |
| Rim diameter | 21" |
| Circumference | 86.38" · 2.194 m |
| Revolutions per mile | 733 (456 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" | +3.94% | 0 mm | 62.4 mph | compare → |
| 265/35R21 | 28.30" | +2.94% | -10 mm | 61.8 mph | compare → |
| 245/35R21 | 27.75" | +0.93% | -30 mm | 60.6 mph | compare → |
| 325/30R21 | 28.68" | +4.30% | +50 mm | 62.6 mph | compare → |
| 255/35R21 | 28.03" | +1.93% | -20 mm | 61.2 mph | compare → |
| 315/30R21 | 28.44" | +3.44% | +40 mm | 62.1 mph | compare → |
| 285/35R21 | 28.85" | +4.94% | +10 mm | 63.0 mph | compare → |
| 245/40R21 | 28.72" | +4.44% | -30 mm | 62.7 mph | compare → |
| 295/30R21 | 27.97" | +1.72% | +20 mm | 61.0 mph | compare → |
| 305/30R21 | 28.20" | +2.58% | +30 mm | 61.5 mph | compare → |
| 285/30R21 | 27.73" | +0.86% | +10 mm | 60.5 mph | compare → |
| 255/30R21 | 27.02" | -1.72% | -20 mm | 59.0 mph | calculate → |
| 355/25R21 | 27.99" | +1.79% | +80 mm | 61.1 mph | calculate → |
| 295/25R21 | 26.81" | -2.51% | +20 mm | 58.5 mph | calculate → |
| 265/30R21 | 27.26" | -0.86% | -10 mm | 59.5 mph | calculate → |
| 325/25R21 | 27.40" | -0.36% | +50 mm | 59.8 mph | calculate → |
| 345/25R21 | 27.79" | +1.07% | +70 mm | 60.6 mph | calculate → |
| 305/25R21 | 27.00" | -1.79% | +30 mm | 58.9 mph | calculate → |
| 245/30R21 | 26.79" | -2.58% | -30 mm | 58.5 mph | calculate → |
| 275/25R21 | 26.41" | -3.94% | 0 mm | 57.6 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" | +0.80% | -30 mm | 60.5 mph | compare → |
| 275/35R20 common | 27.58" | +0.30% | 0 mm | 60.2 mph | compare → |
| 265/35R20 common | 27.30" | -0.70% | -10 mm | 59.6 mph | compare → |
| 315/30R20 | 27.44" | -0.20% | +40 mm | 59.9 mph | compare → |
| 235/40R20 | 27.40" | -0.34% | -40 mm | 59.8 mph | calculate → |
| 325/30R20 | 27.68" | +0.66% | +50 mm | 60.4 mph | calculate → |
| 215/45R20 | 27.62" | +0.44% | -60 mm | 60.3 mph | calculate → |
| 235/30R22 | 27.55" | +0.20% | -40 mm | 60.1 mph | calculate → |
| 285/25R22 | 27.61" | +0.42% | +10 mm | 60.2 mph | calculate → |
| 195/50R20 | 27.68" | +0.66% | -80 mm | 60.4 mph | calculate → |
| 145/65R20 | 27.42" | -0.27% | -130 mm | 59.8 mph | calculate → |
| 175/55R20 | 27.58" | +0.30% | -100 mm | 60.2 mph | calculate → |
| 275/25R22 | 27.41" | -0.30% | 0 mm | 59.8 mph | calculate → |
| 155/60R20 | 27.32" | -0.63% | -120 mm | 59.6 mph | calculate → |
Try another size against 275/30R21
Questions
What size is 275/30R21 in inches?
275/30R21 is about 27.5" tall and 10.8" wide on a 21-inch rim — roughly a 27.5x11.00R21 in inch sizing.
What does 275/30R21 mean?
275 mm section width, sidewall 30% of the width (3.25"), radial construction, 21-inch rim.
What tire sizes are equivalent to 275/30R21?
On the same 21" rim, within 3% of the diameter: 325/25R21 (-0.36%), 265/30R21 (-0.86%), 285/30R21 (+0.86%), 245/35R21 (+0.93%), 345/25R21 (+1.07%), 255/30R21 (-1.72%).
How many revolutions per mile does a 275/30R21 tire make?
About 733 revolutions per mile (circumference 86.4").
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.