275/40R21 dimensions
| Measure | Inches | Millimetres |
|---|---|---|
| Overall height | 29.66 in | 753 mm |
| Section width | 10.83 in | 275 mm |
| Sidewall height | 4.33 in | 110.0 mm |
| Wheel diameter | 21 in | 533 mm |
| Circumference | 93.2 in | 2,367 mm |
| Revolutions per mile | 679.9 |
The math
| Step | Math | Result |
|---|---|---|
| Sidewall | 275 × 40% = 110.0 mm ÷ 25.4 | 4.33 in |
| Overall height | 21 + 2 × 4.33 | 29.66 in |
| Width | 275 mm ÷ 25.4 | 10.83 in |
| Circumference | π × 29.66 | 93.2 in |
| Revs per mile | 63,360 ÷ 93.2 | 679.9 |
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 275/40R21, 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 | 285/40R21 (compare) | 30.0 in | +1.1% | 60.6 mph | Close match |
| Narrower | 265/40R21 (compare) | 29.3 in | -1.1% | 59.4 mph | Close match |
| Taller sidewall | 275/45R21 (compare) | 30.7 in | +3.7% | 62.2 mph | Check clearance |
| Shorter sidewall | 275/35R21 (compare) | 28.6 in | -3.7% | 57.8 mph | Check clearance |
| Wider, shorter sidewall | 285/35R21 (compare) | 28.9 in | -2.7% | 58.4 mph | Close match |
| Narrower, taller sidewall | 265/45R21 (compare) | 30.4 in | +2.5% | 61.5 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% | -30 mm |
| 305/40R20 (compare) | 29.6 in | -0.2% | +30 mm |
| 275/45R20 (compare) | 29.7 in | +0.3% | +0 mm |
| 265/45R20 (compare) | 29.4 in | -0.9% | -10 mm |
22 in wheels (one wheel size larger)
| Size | Height | Height change | Width change |
|---|---|---|---|
| 245/40R22 (compare) | 29.7 in | +0.2% | -30 mm |
| 275/35R22 (compare) | 29.6 in | -0.3% | +0 mm |
| 285/35R22 (compare) | 29.9 in | +0.7% | +10 mm |
| 265/35R22 (compare) | 29.3 in | -1.2% | -10 mm |
23 in wheels (two wheel sizes larger)
| Size | Height | Height change | Width change |
|---|---|---|---|
| 285/30R23 (compare) | 29.7 in | +0.2% | +10 mm |
| 245/35R23 (compare) | 29.8 in | +0.3% | -30 mm |
| 275/30R23 (compare) | 29.5 in | -0.6% | +0 mm |
| 295/30R23 (compare) | 30.0 in | +1.0% | +20 mm |
Try it with your numbers
Compare 275/40R21 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 · 265/45R21 · 275/45R21.