305/35R21 tire size
305/35R21 is a metric size: 29.4" tall, 12.0" wide, on a 21" rim — about a 29.5x12.00R21. The sidewall is 4.2" and the tire turns 686 times per mile.
305/35R21 specs
| Overall diameter (height) | 29.41" · 747 mm |
|---|---|
| Section width | 12.01" · 305 mm |
| Sidewall height | 4.20" · 107 mm (35% of width) |
| Rim diameter | 21" |
| Circumference | 92.38" · 2.346 m |
| Revolutions per mile | 686 (426 per km) |
| Inch (flotation) equivalent | 29.5x12.00R21 |
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 | |
|---|---|---|---|---|---|
| 265/40R21 common | 29.35" | -0.20% | -40 mm | 59.9 mph | calculate → |
| 275/35R21 common | 28.58" | -2.81% | -30 mm | 58.3 mph | calculate → |
| 295/35R21 | 29.13" | -0.94% | -10 mm | 59.4 mph | calculate → |
| 275/45R21 | 30.74" | +4.55% | -30 mm | 62.7 mph | calculate → |
| 255/40R21 | 29.03" | -1.27% | -50 mm | 59.2 mph | calculate → |
| 265/35R21 | 28.30" | -3.75% | -40 mm | 57.8 mph | calculate → |
| 295/40R21 | 30.29" | +3.01% | -10 mm | 61.8 mph | calculate → |
| 285/40R21 | 29.98" | +1.94% | -20 mm | 61.2 mph | calculate → |
| 265/45R21 | 30.39" | +3.35% | -40 mm | 62.0 mph | calculate → |
| 325/30R21 | 28.68" | -2.48% | +20 mm | 58.5 mph | calculate → |
| 275/40R21 | 29.66" | +0.87% | -30 mm | 60.5 mph | calculate → |
| 255/35R21 | 28.03" | -4.69% | -50 mm | 57.2 mph | calculate → |
| 285/35R21 | 28.85" | -1.87% | -20 mm | 58.9 mph | calculate → |
| 315/30R21 | 28.44" | -3.28% | +10 mm | 58.0 mph | calculate → |
| 315/35R21 | 29.68" | +0.94% | +10 mm | 60.6 mph | calculate → |
| 245/40R21 | 28.72" | -2.34% | -60 mm | 58.6 mph | calculate → |
| 305/30R21 | 28.20" | -4.08% | 0 mm | 57.5 mph | calculate → |
| 295/30R21 | 27.97" | -4.89% | -10 mm | 57.1 mph | calculate → |
| 255/45R21 | 30.04" | +2.14% | -50 mm | 61.3 mph | calculate → |
| 245/45R21 | 29.68" | +0.94% | -60 mm | 60.6 mph | calculate → |
| 235/50R21 | 30.25" | +2.88% | -70 mm | 61.7 mph | calculate → |
| 355/25R21 | 27.99" | -4.82% | +50 mm | 57.1 mph | calculate → |
| 235/45R21 | 29.33" | -0.27% | -70 mm | 59.8 mph | calculate → |
| 335/30R21 | 28.91" | -1.67% | +30 mm | 59.0 mph | calculate → |
| 345/30R21 | 29.15" | -0.87% | +40 mm | 59.5 mph | calculate → |
| 225/45R21 | 28.97" | -1.47% | -80 mm | 59.1 mph | calculate → |
| 305/40R21 | 30.61" | +4.08% | 0 mm | 62.5 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 | |
|---|---|---|---|---|---|
| 245/50R20 common | 29.65" | +0.82% | -60 mm | 60.5 mph | calculate → |
| 265/45R20 common | 29.39" | -0.05% | -40 mm | 60.0 mph | calculate → |
| 265/35R22 | 29.30" | -0.35% | -40 mm | 59.8 mph | calculate → |
| 295/40R20 | 29.29" | -0.39% | -10 mm | 59.8 mph | calculate → |
| 235/50R20 | 29.25" | -0.52% | -70 mm | 59.7 mph | calculate → |
| 275/35R22 | 29.58" | +0.59% | -30 mm | 60.4 mph | calculate → |
| 305/40R20 | 29.61" | +0.68% | 0 mm | 60.4 mph | calculate → |
| 315/30R22 | 29.44" | +0.12% | +10 mm | 60.1 mph | calculate → |
| 305/30R22 | 29.20" | -0.68% | 0 mm | 59.6 mph | calculate → |
| 325/30R22 | 29.68" | +0.92% | +20 mm | 60.6 mph | calculate → |
| 175/70R20 | 29.65" | +0.82% | -130 mm | 60.5 mph | calculate → |
Try another size against 305/35R21
Questions
What size is 305/35R21 in inches?
305/35R21 is about 29.4" tall and 12.0" wide on a 21-inch rim — roughly a 29.5x12.00R21 in inch sizing.
What does 305/35R21 mean?
305 mm section width, sidewall 35% of the width (4.20"), radial construction, 21-inch rim.
What tire sizes are equivalent to 305/35R21?
On the same 21" rim, within 3% of the diameter: 265/40R21 (-0.20%), 235/45R21 (-0.27%), 275/40R21 (+0.87%), 345/30R21 (-0.87%), 245/45R21 (+0.94%), 295/35R21 (-0.94%).
How many revolutions per mile does a 305/35R21 tire make?
About 686 revolutions per mile (circumference 92.4").
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.