A 205/55R16 tire has a 112.8 mm sidewall and an overall diameter of 632 mm, so it turns about 504 times per kilometre.
| Tire size | Width (mm) | Sidewall height (mm) | Overall diameter (mm) | Overall diameter (in) | Revolutions per km |
|---|---|---|---|---|---|
| 175/65R14 | 175 | 113.8 | 583 | 23.0 | 546 |
| 185/65R15 | 185 | 120.3 | 622 | 24.5 | 512 |
| 195/65R15 | 195 | 126.8 | 635 | 25.0 | 502 |
| 205/55R16 | 205 | 112.8 | 632 | 24.9 | 504 |
| 205/60R16 | 205 | 123.0 | 652 | 25.7 | 488 |
| 215/55R17 | 215 | 118.3 | 668 | 26.3 | 476 |
| 215/60R16 | 215 | 129.0 | 664 | 26.2 | 479 |
| 225/45R17 | 225 | 101.3 | 634 | 25.0 | 502 |
| 225/45R18 | 225 | 101.3 | 660 | 26.0 | 483 |
| 225/60R17 | 225 | 135.0 | 702 | 27.6 | 454 |
| 225/65R17 | 225 | 146.3 | 724 | 28.5 | 439 |
| 235/45R18 | 235 | 105.8 | 669 | 26.3 | 476 |
| 235/55R19 | 235 | 129.3 | 741 | 29.2 | 430 |
| 235/60R18 | 235 | 141.0 | 739 | 29.1 | 431 |
| 235/65R17 | 235 | 152.8 | 737 | 29.0 | 432 |
| 245/40R19 | 245 | 98.0 | 679 | 26.7 | 469 |
| 245/45R18 | 245 | 110.3 | 678 | 26.7 | 470 |
| 245/60R18 | 245 | 147.0 | 751 | 29.6 | 424 |
| 255/55R20 | 255 | 140.3 | 789 | 31.0 | 404 |
| 265/65R17 | 265 | 172.3 | 776 | 30.6 | 410 |
| 265/70R17 | 265 | 185.5 | 803 | 31.6 | 396 |
| 275/55R20 | 275 | 151.3 | 811 | 31.9 | 393 |
| 275/60R20 | 275 | 165.0 | 838 | 33.0 | 380 |
| 285/70R17 | 285 | 199.5 | 831 | 32.7 | 383 |
How it is computed
In a size such as 205/55R16, 205 is the width in mm, 55 the sidewall height as a percentage of the width, and 16 the rim diameter in inches. Sidewall = width × aspect ÷ 100; diameter = rim × 25.4 + 2 × sidewall; revolutions per km = 1,000 ÷ (π × diameter in metres).
FAQ
How much can the diameter change when I switch sizes?+
Keep the new overall diameter within about 3% of the original so the speedometer, ABS and stability control stay accurate.
Why do my tires turn slightly more often than the table says?+
The table uses the nominal unloaded diameter. Under load and as the tread wears, the rolling radius gets a little smaller.