245/30R21 tire size
245/30R21 is a metric size: 26.8" tall, 9.6" wide, on a 21" rim — about a 27x9.50R21. The sidewall is 2.9" and the tire turns 753 times per mile.
245/30R21 specs
| Overall diameter (height) | 26.79" · 680 mm |
|---|---|
| Section width | 9.65" · 245 mm |
| Sidewall height | 2.89" · 74 mm (30% of width) |
| Rim diameter | 21" |
| Circumference | 84.16" · 2.138 m |
| Revolutions per mile | 753 (468 per km) |
| Inch (flotation) equivalent | 27x9.50R21 |
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 | |
|---|---|---|---|---|---|
| 245/35R21 | 27.75" | +3.60% | 0 mm | 62.2 mph | calculate → |
| 255/35R21 | 28.03" | +4.63% | +10 mm | 62.8 mph | calculate → |
| 295/30R21 | 27.97" | +4.41% | +50 mm | 62.6 mph | calculate → |
| 285/30R21 | 27.73" | +3.53% | +40 mm | 62.1 mph | calculate → |
| 275/30R21 | 27.50" | +2.65% | +30 mm | 61.6 mph | calculate → |
| 255/30R21 | 27.02" | +0.88% | +10 mm | 60.5 mph | calculate → |
| 355/25R21 | 27.99" | +4.48% | +110 mm | 62.7 mph | calculate → |
| 295/25R21 | 26.81" | +0.07% | +50 mm | 60.0 mph | calculate → |
| 265/30R21 | 27.26" | +1.76% | +20 mm | 61.1 mph | calculate → |
| 305/25R21 | 27.00" | +0.81% | +60 mm | 60.5 mph | calculate → |
| 325/25R21 | 27.40" | +2.28% | +80 mm | 61.4 mph | calculate → |
| 345/25R21 | 27.79" | +3.75% | +100 mm | 62.2 mph | calculate → |
| 275/25R21 | 26.41" | -1.40% | +30 mm | 59.2 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 | |
|---|---|---|---|---|---|
| 245/35R20 common | 26.75" | -0.13% | 0 mm | 59.9 mph | calculate → |
| 255/35R20 common | 27.03" | +0.90% | +10 mm | 60.5 mph | calculate → |
| 285/30R20 common | 26.73" | -0.21% | +40 mm | 59.9 mph | calculate → |
| 295/30R20 | 26.97" | +0.68% | +50 mm | 60.4 mph | calculate → |
| 335/25R20 | 26.59" | -0.72% | +90 mm | 59.6 mph | calculate → |
| 345/25R20 | 26.79" | +0.01% | +100 mm | 60.0 mph | calculate → |
| 145/60R20 | 26.85" | +0.24% | -100 mm | 60.1 mph | calculate → |
Try another size against 245/30R21
Questions
What size is 245/30R21 in inches?
245/30R21 is about 26.8" tall and 9.6" wide on a 21-inch rim — roughly a 27x9.50R21 in inch sizing.
What does 245/30R21 mean?
245 mm section width, sidewall 30% of the width (2.89"), radial construction, 21-inch rim.
What tire sizes are equivalent to 245/30R21?
On the same 21" rim, within 3% of the diameter: 295/25R21 (+0.07%), 305/25R21 (+0.81%), 255/30R21 (+0.88%), 275/25R21 (-1.40%), 265/30R21 (+1.76%), 325/25R21 (+2.28%).
How many revolutions per mile does a 245/30R21 tire make?
About 753 revolutions per mile (circumference 84.2").
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.