245/45R21 dimensions
| Measure | Inches | Millimetres |
|---|---|---|
| Overall height | 29.68 in | 754 mm |
| Section width | 9.65 in | 245 mm |
| Sidewall height | 4.34 in | 110.2 mm |
| Wheel diameter | 21 in | 533 mm |
| Circumference | 93.2 in | 2,368 mm |
| Revolutions per mile | 679.5 |
The math
| Step | Math | Result |
|---|---|---|
| Sidewall | 245 × 45% = 110.2 mm ÷ 25.4 | 4.34 in |
| Overall height | 21 + 2 × 4.34 | 29.68 in |
| Width | 245 mm ÷ 25.4 | 9.65 in |
| Circumference | π × 29.68 | 93.2 in |
| Revs per mile | 63,360 ÷ 93.2 | 679.5 |
With a 4.3 in sidewall this is a medium sidewall: a balance of cushion and response. Real tires vary by brand and model, and the loaded radius under the vehicle is a bit smaller than this unloaded figure.
One step either way on a 21 in wheel
Each row changes one thing and shows the height change against 245/45R21, plus what 60 mph on the speedometer would really be if you swapped to that size.
| Change | Size | Height | Height change | 60 mph shows as | Verdict |
|---|---|---|---|---|---|
| Wider | 255/45R21 (compare) | 30.0 in | +1.2% | 60.7 mph | Close match |
| Narrower | 235/45R21 (compare) | 29.3 in | -1.2% | 59.3 mph | Close match |
| Taller sidewall | 245/50R21 (compare) | 30.6 in | +3.2% | 61.9 mph | Check clearance |
| Shorter sidewall | 245/40R21 (compare) | 28.7 in | -3.2% | 58.1 mph | Check clearance |
| Wider, shorter sidewall | 255/40R21 (compare) | 29.0 in | -2.2% | 58.7 mph | Close match |
| Narrower, taller sidewall | 235/50R21 (compare) | 30.3 in | +1.9% | 61.2 mph | Close match |
Calculated sizes within ±3% on other wheels
Plus and minus sizes that keep the overall height within about 3% (a rule of thumb from Discount Tire and 1010tires), widths within 30 mm. Calculated, not a list of tires on sale: check that a tire exists in that size.
20 in wheels (one wheel size smaller)
| Size | Height | Height change | Width change |
|---|---|---|---|
| 245/50R20 (compare) | 29.6 in | -0.1% | +0 mm |
| 225/55R20 (compare) | 29.7 in | +0.2% | -20 mm |
| 275/45R20 (compare) | 29.7 in | +0.2% | +30 mm |
| 265/45R20 (compare) | 29.4 in | -1.0% | +20 mm |
22 in wheels (one wheel size larger)
| Size | Height | Height change | Width change |
|---|---|---|---|
| 245/40R22 (compare) | 29.7 in | +0.1% | +0 mm |
| 215/45R22 (compare) | 29.6 in | -0.2% | -30 mm |
| 275/35R22 (compare) | 29.6 in | -0.3% | +30 mm |
| 235/40R22 (compare) | 29.4 in | -0.9% | -10 mm |
23 in wheels (two wheel sizes larger)
| Size | Height | Height change | Width change |
|---|---|---|---|
| 245/35R23 (compare) | 29.8 in | +0.2% | +0 mm |
| 215/40R23 (compare) | 29.8 in | +0.3% | -30 mm |
| 275/30R23 (compare) | 29.5 in | -0.6% | +30 mm |
| 235/35R23 (compare) | 29.5 in | -0.7% | -10 mm |
Try it with your numbers
Compare 245/45R21 with another size · Convert to metric or find a 33 in size · Sizes that fit my wheel
Calculated from the size alone. Real tires vary a little by brand and model, and the loaded radius is a bit smaller. Confirm the wheel width range, clearance, load index and speed rating for your vehicle. See how to read a tire size, the load index chart and the speed rating chart.
Browse: all sizes in inches · 305/55R20 · 255/40R21.