305/30R21 tire size in inches
A 305/30R21 tire measures
28.2" tall × 12.0" wide
3.60" sidewall on a 21" wheel. 715 revolutions per mile.
305/30R21 means a tire 305 mm wide, with sidewalls 30% as tall as the tire is wide (92 mm), radial construction (R), for a 21 inch wheel.
305/30R21 specs
| Overall diameter (height) | 28.20 inches (716 mm) |
|---|---|
| Section width | 12.01 inches (305 mm) |
| Sidewall height | 3.60 inches (92 mm) |
| Wheel (rim) diameter | 21 inches |
| Circumference | 88.6 inches (2,251 mm) |
| Revolutions per mile | 715 |
| Revolutions per kilometer | 444 |
| Approximate rim width | 10.0" to 11.5" |
| In inches (flotation style) | 28.2x12.0R21 |
| Aspect ratio | 30% |
Calculated from the size. Real tires differ by brand, model and tread depth, typically by a few tenths of an inch.
Sizes that can replace 305/30R21 on a 21" wheel
These 21" sizes are within 3% of 305/30R21's overall diameter, the range most tire shops treat as interchangeable.
| Size | Diameter | Width | Difference | Real speed at 60 | |
|---|---|---|---|---|---|
| 265/35R21 | 28.30" | 10.43" | +0.3% | 60.2 mph | Compare |
| 225/40R21 | 28.09" | 8.86" | −0.4% | 59.7 mph | Compare |
| 255/35R21 | 28.03" | 10.04" | −0.6% | 59.6 mph | Compare |
| 235/40R21 | 28.40" | 9.25" | +0.7% | 60.4 mph | Compare |
| 355/25R21 | 27.99" | 13.98" | −0.8% | 59.5 mph | Compare |
| 295/30R21 | 27.97" | 11.61" | −0.8% | 59.5 mph | Compare |
| 315/30R21 | 28.44" | 12.40" | +0.8% | 60.5 mph | Compare |
| 275/35R21 | 28.58" | 10.83" | +1.3% | 60.8 mph | Compare |
| 345/25R21 | 27.79" | 13.58" | −1.5% | 59.1 mph | Compare |
| 245/35R21 | 27.75" | 9.65" | −1.6% | 59.0 mph | Compare |
| 285/30R21 | 27.73" | 11.22" | −1.7% | 59.0 mph | Compare |
| 325/30R21 | 28.68" | 12.80" | +1.7% | 61.0 mph | Compare |
Same height on other wheel sizes (plus and minus sizing)
| Size | Wheel | Diameter | Difference | |
|---|---|---|---|---|
| 315/25R22 | 22" | 28.20" | 0.0% | Compare |
| 285/50R17 | 17" | 28.22" | +0.1% | Compare |
| 235/55R18 | 18" | 28.18" | −0.1% | Compare |
| 335/35R19 | 19" | 28.23" | +0.1% | Compare |
| 225/80R14 | 14" | 28.17" | −0.1% | Compare |
| 325/40R18 | 18" | 28.24" | +0.1% | Compare |
| 315/45R17 | 17" | 28.16" | −0.2% | Compare |
| 215/60R18 | 18" | 28.16" | −0.2% | Compare |
| 235/50R19 | 19" | 28.25" | +0.2% | Compare |
| 345/30R20 | 20" | 28.15" | −0.2% | Compare |
| 265/30R22 | 22" | 28.26" | +0.2% | Compare |
| 295/35R20 | 20" | 28.13" | −0.3% | Compare |
One size up or down
- 295/30R21narrower: 28.0" × 11.6"
- 315/30R21wider: 28.4" × 12.4"
- 305/25R21lower profile: 27.0" × 12.0"
- 305/35R21taller sidewall: 29.4" × 12.0"
Compare 305/30R21 with another size
305/30R21 side-by-side comparisons
- 305/30R21 vs 345/30R20
- 305/30R21 vs 305/25R21
- 305/30R21 vs 285/30R21
- 305/30R21 vs 295/30R21
- 305/30R21 vs 315/30R21
- 305/30R21 vs 325/30R21
- 305/30R21 vs 305/35R21
- 305/30R21 vs 305/40R21
- 305/30R21 vs 315/25R21
- 305/30R21 vs 325/25R21
- 305/30R21 vs 315/25R22
- 305/30R21 vs 285/35R21
- 305/30R21 vs 295/35R21
Questions
- How tall is a 305/30R21 tire?
- A 305/30R21 tire is 28.2 inches tall (716 mm), calculated from the size. It is 12.0 inches wide with 3.6 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
- What does 305/30R21 mean?
- 305/30R21 means a tire 305 mm wide, with sidewalls 30% as tall as the tire is wide (92 mm), radial construction (R), for a 21 inch wheel.
- How many revolutions per mile does a 305/30R21 tire make?
- About 715 revolutions per mile, based on a circumference of 88.6 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
- What rim width fits a 305/30R21 tire?
- Roughly 10.0" to 11.5". Check the tire maker's approved rim range for the exact model before buying wheels.
- Can I use 265/35R21 instead of 305/30R21?
- 265/35R21 is +0.10 inches (+0.3%) in overall diameter, so at an indicated 60 mph you would be doing 60.2 mph. Differences under 3% are usually fine, but check clearance, load index and your vehicle's placard.