305/30R21 tire size
A 305/30R21 tire is 28.20 inches (716.4 mm) tall, 12.01 in (305 mm) wide and fits a 21-inch wheel. In inch notation it is roughly a 28.2x12.0R21 — a "28-inch" tire.
| Overall diameter | 28.20 in | 716.4 mm |
|---|---|---|
| Section width | 12.01 in | 305 mm |
| Sidewall height | 3.60 in | 91.5 mm |
| Circumference | 88.61 in | 2,251 mm |
| Revolutions | 715.1 per mile | 444.3 per km |
| Rim diameter | 21 in | 533.4 mm |
Compare 305/30R21 with another size
Alternative sizes on the same 21-inch wheel
Sizes in use within ±3 % of the overall diameter of 305/30R21:
Plus and minus sizes for 305/30R21
| Size | Wheel | Diameter | Difference |
|---|---|---|---|
| 295/40R19 | Minus 2 (19 in) | 28.29 in | +0.31% |
| 285/40R19 | Minus 2 (19 in) | 27.98 in | −0.81% |
| 345/35R19 | Minus 2 (19 in) | 28.51 in | +1.07% |
| 275/45R19 | Minus 2 (19 in) | 28.74 in | +1.91% |
| 345/30R20 | Minus 1 (20 in) | 28.15 in | −0.20% |
| 295/35R20 | Minus 1 (20 in) | 28.13 in | −0.27% |
| 305/35R20 | Minus 1 (20 in) | 28.41 in | +0.71% |
| 335/30R20 | Minus 1 (20 in) | 27.91 in | −1.03% |
| 285/30R22 | Plus 1 (22 in) | 28.73 in | +1.87% |
| 295/30R22 | Plus 1 (22 in) | 28.97 in | +2.71% |
| 355/25R22 | Plus 1 (22 in) | 28.99 in | +2.78% |
Vehicles approved with 305/30R21 tires
Models whose Swiss type approval lists 305/30R21 as a standard or optional size (251 approvals in total). Always check your own vehicle's placard or papers.
Source: Swiss Federal Roads Office (FEDRO/ASTRA), open government data. Original data (downloaded 2026-09-29). Data processed by us; errors in processing are ours, not the publisher's.
Nearby 21-inch sizes
Reading the 305/30R21 size
- 305 — section width in millimetres (12.01 in).
- 30 — aspect ratio: the sidewall is 30 % of the width, 91.5 mm.
- R — radial construction (ZR on the sidewall means a high-speed rated radial; the dimensions are the same).
- 21 — fits a 21-inch diameter wheel.
The load index and speed rating (for example 91V) follow the size on the sidewall. They must meet at least the values on your vehicle's tire placard.