305/25R21 tire size in inches
A 305/25R21 tire measures
27.0" tall × 12.0" wide
3.00" sidewall on a 21" wheel. 747 revolutions per mile.
305/25R21 means a tire 305 mm wide, with sidewalls 25% as tall as the tire is wide (76 mm), radial construction (R), for a 21 inch wheel.
305/25R21 specs
| Overall diameter (height) | 27.00 inches (686 mm) |
|---|---|
| Section width | 12.01 inches (305 mm) |
| Sidewall height | 3.00 inches (76 mm) |
| Wheel (rim) diameter | 21 inches |
| Circumference | 84.8 inches (2,155 mm) |
| Revolutions per mile | 747 |
| Revolutions per kilometer | 464 |
| Approximate rim width | 10.0" to 11.5" |
| In inches (flotation style) | 27.0x12.0R21 |
| Aspect ratio | 25% |
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 305/25R21 on a 21" wheel
These 21" sizes are within 3% of 305/25R21's overall diameter, the range most tire shops treat as interchangeable.
| Size | Diameter | Width | Difference | Real speed at 60 | |
|---|---|---|---|---|---|
| 255/30R21 | 27.02" | 10.04" | +0.1% | 60.0 mph | Compare |
| 295/25R21 | 26.81" | 11.61" | −0.7% | 59.6 mph | Compare |
| 225/35R21 | 27.20" | 8.86" | +0.7% | 60.4 mph | Compare |
| 315/25R21 | 27.20" | 12.40" | +0.7% | 60.4 mph | Compare |
| 245/30R21 | 26.79" | 9.65" | −0.8% | 59.5 mph | Compare |
| 265/30R21 | 27.26" | 10.43" | +0.9% | 60.6 mph | Compare |
| 285/25R21 | 26.61" | 11.22" | −1.5% | 59.1 mph | Compare |
| 325/25R21 | 27.40" | 12.80" | +1.5% | 60.9 mph | Compare |
| 235/30R21 | 26.55" | 9.25" | −1.7% | 59.0 mph | Compare |
| 235/35R21 | 27.48" | 9.25" | +1.7% | 61.0 mph | Compare |
| 275/30R21 | 27.50" | 10.83" | +1.8% | 61.1 mph | Compare |
| 275/25R21 | 26.41" | 10.83" | −2.2% | 58.7 mph | Compare |
Same height on other wheel sizes (plus and minus sizing)
| Size | Wheel | Diameter | Difference | |
|---|---|---|---|---|
| 215/65R16 | 16" | 27.00" | 0.0% | Compare |
| 255/25R22 | 22" | 27.02" | +0.1% | Compare |
| 355/25R20 | 20" | 26.99" | −0.1% | Compare |
| 175/80R16 | 16" | 27.02" | +0.1% | Compare |
| 195/65R17 | 17" | 26.98" | −0.1% | Compare |
| 235/65R15 | 15" | 27.03" | +0.1% | Compare |
| 255/35R20 | 20" | 27.03" | +0.1% | Compare |
| 255/40R19 | 19" | 27.03" | +0.1% | Compare |
| 285/40R18 | 18" | 26.98" | −0.1% | Compare |
| 225/45R19 | 19" | 26.97" | −0.1% | Compare |
| 255/45R18 | 18" | 27.04" | +0.1% | Compare |
| 255/50R17 | 17" | 27.04" | +0.1% | Compare |
One size up or down
- 295/25R21narrower: 26.8" × 11.6"
- 315/25R21wider: 27.2" × 12.4"
- 305/30R21taller sidewall: 28.2" × 12.0"
Compare 305/25R21 with another size
Questions
- How tall is a 305/25R21 tire?
- A 305/25R21 tire is 27.0 inches tall (686 mm), calculated from the size. It is 12.0 inches wide with 3.0 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
- What does 305/25R21 mean?
- 305/25R21 means a tire 305 mm wide, with sidewalls 25% as tall as the tire is wide (76 mm), radial construction (R), for a 21 inch wheel.
- How many revolutions per mile does a 305/25R21 tire make?
- About 747 revolutions per mile, based on a circumference of 84.8 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
- What rim width fits a 305/25R21 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 255/30R21 instead of 305/25R21?
- 255/30R21 is +0.02 inches (+0.1%) in overall diameter, so at an indicated 60 mph you would be doing 60.0 mph. Differences under 3% are usually fine, but check clearance, load index and your vehicle's placard.