325/30R21 tire size
325/30R21 is a metric size: 28.7" tall, 12.8" wide, on a 21" rim — about a 28.5x13.00R21. The sidewall is 3.8" and the tire turns 703 times per mile.
325/30R21 specs
| Overall diameter (height) | 28.68" · 728 mm |
|---|---|
| Section width | 12.80" · 325 mm |
| Sidewall height | 3.84" · 98 mm (30% of width) |
| Rim diameter | 21" |
| Circumference | 90.09" · 2.288 m |
| Revolutions per mile | 703 (437 per km) |
| Inch (flotation) equivalent | 28.5x13.00R21 |
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" | +2.33% | -60 mm | 61.4 mph | compare → |
| 275/35R21 common | 28.58" | -0.34% | -50 mm | 59.8 mph | compare → |
| 295/35R21 | 29.13" | +1.58% | -30 mm | 60.9 mph | compare → |
| 255/40R21 | 29.03" | +1.24% | -70 mm | 60.7 mph | compare → |
| 265/35R21 | 28.30" | -1.30% | -60 mm | 59.2 mph | compare → |
| 245/35R21 | 27.75" | -3.23% | -80 mm | 58.1 mph | compare → |
| 285/40R21 | 29.98" | +4.53% | -40 mm | 62.7 mph | compare → |
| 275/40R21 | 29.66" | +3.43% | -50 mm | 62.1 mph | compare → |
| 255/35R21 | 28.03" | -2.27% | -70 mm | 58.6 mph | compare → |
| 285/35R21 | 28.85" | +0.62% | -40 mm | 60.4 mph | compare → |
| 315/30R21 | 28.44" | -0.82% | -10 mm | 59.5 mph | compare → |
| 245/40R21 | 28.72" | +0.14% | -80 mm | 60.1 mph | compare → |
| 315/35R21 | 29.68" | +3.50% | -10 mm | 62.1 mph | compare → |
| 305/30R21 | 28.20" | -1.65% | -20 mm | 59.0 mph | compare → |
| 295/30R21 | 27.97" | -2.47% | -30 mm | 58.5 mph | compare → |
| 285/30R21 | 27.73" | -3.29% | -40 mm | 58.0 mph | compare → |
| 255/45R21 | 30.04" | +4.74% | -70 mm | 62.8 mph | compare → |
| 245/45R21 | 29.68" | +3.50% | -80 mm | 62.1 mph | compare → |
| 275/30R21 | 27.50" | -4.12% | -50 mm | 57.5 mph | compare → |
| 355/25R21 | 27.99" | -2.40% | +30 mm | 58.6 mph | calculate → |
| 235/45R21 | 29.33" | +2.27% | -90 mm | 61.4 mph | calculate → |
| 335/30R21 | 28.91" | +0.82% | +10 mm | 60.5 mph | calculate → |
| 305/35R21 | 29.41" | +2.54% | -20 mm | 61.5 mph | calculate → |
| 345/30R21 | 29.15" | +1.65% | +20 mm | 61.0 mph | calculate → |
| 265/30R21 | 27.26" | -4.94% | -60 mm | 57.0 mph | calculate → |
| 225/45R21 | 28.97" | +1.03% | -100 mm | 60.6 mph | calculate → |
| 345/25R21 | 27.79" | -3.09% | +20 mm | 58.1 mph | calculate → |
| 325/25R21 | 27.40" | -4.46% | 0 mm | 57.3 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 | |
|---|---|---|---|---|---|
| 245/45R20 common | 28.68" | +0.01% | -80 mm | 60.0 mph | compare → |
| 275/40R20 common | 28.66" | -0.05% | -50 mm | 60.0 mph | compare → |
| 315/35R20 common | 28.68" | +0.01% | -10 mm | 60.0 mph | compare → |
| 305/35R20 | 28.41" | -0.95% | -20 mm | 59.4 mph | compare → |
| 285/30R22 | 28.73" | +0.19% | -40 mm | 60.1 mph | compare → |
| 335/25R22 | 28.59" | -0.29% | +10 mm | 59.8 mph | calculate → |
| 325/35R20 | 28.96" | +0.97% | 0 mm | 60.6 mph | calculate → |
| 275/30R22 | 28.50" | -0.63% | -50 mm | 59.6 mph | calculate → |
| 195/55R20 | 28.44" | -0.81% | -130 mm | 59.5 mph | calculate → |
Try another size against 325/30R21
Questions
What size is 325/30R21 in inches?
325/30R21 is about 28.7" tall and 12.8" wide on a 21-inch rim — roughly a 28.5x13.00R21 in inch sizing.
What does 325/30R21 mean?
325 mm section width, sidewall 30% of the width (3.84"), radial construction, 21-inch rim.
What tire sizes are equivalent to 325/30R21?
On the same 21" rim, within 3% of the diameter: 245/40R21 (+0.14%), 275/35R21 (-0.34%), 285/35R21 (+0.62%), 335/30R21 (+0.82%), 315/30R21 (-0.82%), 225/45R21 (+1.03%).
How many revolutions per mile does a 325/30R21 tire make?
About 703 revolutions per mile (circumference 90.1").
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.