345/30R21 tire size
345/30R21 is a metric size: 29.1" tall, 13.6" wide, on a 21" rim — about a 29x13.50R21. The sidewall is 4.1" and the tire turns 692 times per mile.
345/30R21 specs
| Overall diameter (height) | 29.15" · 740 mm |
|---|---|
| Section width | 13.58" · 345 mm |
| Sidewall height | 4.07" · 103 mm (30% of width) |
| Rim diameter | 21" |
| Circumference | 91.58" · 2.326 m |
| Revolutions per mile | 692 (430 per km) |
| Inch (flotation) equivalent | 29x13.50R21 |
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 | |
|---|---|---|---|---|---|
| 265/40R21 common | 29.35" | +0.68% | -80 mm | 60.4 mph | calculate → |
| 275/35R21 common | 28.58" | -1.96% | -70 mm | 58.8 mph | calculate → |
| 295/35R21 | 29.13" | -0.07% | -50 mm | 60.0 mph | calculate → |
| 255/40R21 | 29.03" | -0.41% | -90 mm | 59.8 mph | calculate → |
| 265/35R21 | 28.30" | -2.90% | -80 mm | 58.3 mph | calculate → |
| 295/40R21 | 30.29" | +3.92% | -50 mm | 62.4 mph | calculate → |
| 245/35R21 | 27.75" | -4.79% | -100 mm | 57.1 mph | calculate → |
| 285/40R21 | 29.98" | +2.84% | -60 mm | 61.7 mph | calculate → |
| 265/45R21 | 30.39" | +4.25% | -80 mm | 62.6 mph | calculate → |
| 325/30R21 | 28.68" | -1.62% | -20 mm | 59.0 mph | calculate → |
| 275/40R21 | 29.66" | +1.76% | -70 mm | 61.1 mph | calculate → |
| 255/35R21 | 28.03" | -3.85% | -90 mm | 57.7 mph | calculate → |
| 285/35R21 | 28.85" | -1.01% | -60 mm | 59.4 mph | calculate → |
| 315/30R21 | 28.44" | -2.43% | -30 mm | 58.5 mph | calculate → |
| 245/40R21 | 28.72" | -1.49% | -100 mm | 59.1 mph | calculate → |
| 315/35R21 | 29.68" | +1.82% | -30 mm | 61.1 mph | calculate → |
| 305/30R21 | 28.20" | -3.24% | -40 mm | 58.1 mph | calculate → |
| 295/30R21 | 27.97" | -4.05% | -50 mm | 57.6 mph | calculate → |
| 255/45R21 | 30.04" | +3.04% | -90 mm | 61.8 mph | calculate → |
| 285/30R21 | 27.73" | -4.86% | -60 mm | 57.1 mph | calculate → |
| 245/45R21 | 29.68" | +1.82% | -100 mm | 61.1 mph | calculate → |
| 235/50R21 | 30.25" | +3.78% | -110 mm | 62.3 mph | calculate → |
| 355/25R21 | 27.99" | -3.98% | +10 mm | 57.6 mph | calculate → |
| 235/45R21 | 29.33" | +0.61% | -110 mm | 60.4 mph | calculate → |
| 335/30R21 | 28.91" | -0.81% | -10 mm | 59.5 mph | calculate → |
| 305/35R21 | 29.41" | +0.88% | -40 mm | 60.5 mph | calculate → |
| 225/45R21 | 28.97" | -0.61% | -120 mm | 59.6 mph | calculate → |
| 345/25R21 | 27.79" | -4.66% | 0 mm | 57.2 mph | calculate → |
| 305/40R21 | 30.61" | +5.00% | -40 mm | 63.0 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 | |
|---|---|---|---|---|---|
| 255/45R20 common | 29.04" | -0.39% | -90 mm | 59.8 mph | calculate → |
| 265/45R20 common | 29.39" | +0.82% | -80 mm | 60.5 mph | calculate → |
| 265/35R22 | 29.30" | +0.53% | -80 mm | 60.3 mph | calculate → |
| 295/40R20 | 29.29" | +0.49% | -50 mm | 60.3 mph | calculate → |
| 285/40R20 | 28.98" | -0.59% | -60 mm | 59.6 mph | calculate → |
| 235/50R20 | 29.25" | +0.35% | -110 mm | 60.2 mph | calculate → |
| 295/30R22 | 28.97" | -0.62% | -50 mm | 59.6 mph | calculate → |
| 315/30R22 | 29.44" | +1.00% | -30 mm | 60.6 mph | calculate → |
| 255/35R22 | 29.03" | -0.42% | -90 mm | 59.7 mph | calculate → |
| 325/35R20 | 28.96" | -0.66% | -20 mm | 59.6 mph | calculate → |
| 305/30R22 | 29.20" | +0.19% | -40 mm | 60.1 mph | calculate → |
| 29x15.00R20 | 29.00" | -0.51% | +36 mm | 59.7 mph | calculate → |
| 29x18.00R20 | 29.00" | -0.51% | +112 mm | 59.7 mph | calculate → |
| 355/25R22 | 28.99" | -0.55% | +10 mm | 59.7 mph | calculate → |
Try another size against 345/30R21
Questions
What size is 345/30R21 in inches?
345/30R21 is about 29.1" tall and 13.6" wide on a 21-inch rim — roughly a 29x13.50R21 in inch sizing.
What does 345/30R21 mean?
345 mm section width, sidewall 30% of the width (4.07"), radial construction, 21-inch rim.
What tire sizes are equivalent to 345/30R21?
On the same 21" rim, within 3% of the diameter: 295/35R21 (-0.07%), 255/40R21 (-0.41%), 235/45R21 (+0.61%), 225/45R21 (-0.61%), 265/40R21 (+0.68%), 335/30R21 (-0.81%).
How many revolutions per mile does a 345/30R21 tire make?
About 692 revolutions per mile (circumference 91.6").
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.