285/60R20 measures 33.5″ overall diameter and 11.2″ section width. Sidewall height is 6.7″, circumference is 105.1″, and the tire turns 603 times per mile. Those figures are geometry off the stamped size, not a brand or load range.
285/60R20 dimensions
| Measurement | Inches | Metric |
|---|---|---|
| Overall diameter | 33.5″ | 850 mm |
| Section width | 11.2″ | 285 mm |
| Sidewall height | 6.7″ | 171 mm |
| Circumference | 105.1″ | 2670 mm |
| Revolutions per mile | 603 | 375 / km |
The stamped width is 285 mm (11.2″). The aspect ratio is 60, so the sidewall is 60% of that width, which is 6.7″. The rim is 20 inches. Overall diameter is the rim plus two sidewalls: 20 + 2 × 6.7″ = 33.5″.
Sizes near 285/60R20
A swap that stays inside about 3% diameter usually keeps the speedometer honest and clears the same well. 305/55R20 is a close neighbour at -0.8% diameter. The percent column opens both stamps in the comparison calculator.
| Size | Diameter | Width | vs 285/60R20 |
|---|---|---|---|
| 305/55R20 | 33.2″ | 12.0″ | -0.8% |
| 33x12.50R20 | 33.0″ | 12.5″ | -1.4% |
| 275/60R20 | 33.0″ | 10.8″ | -1.4% |
| 295/60R20 | 33.9″ | 11.6″ | +1.4% |
| 295/75R16 | 33.4″ | 11.6″ | -0.1% |
| 275/65R20 | 34.1″ | 10.8″ | +1.8% |
How to read the stamped size
285/60R20 is a metric size: width in millimetres, aspect ratio as a percent of that width, then the rim diameter in inches after the R. The how to read tire size page walks the whole sidewall, including load index and speed rating, which this page does not use.
Diameter and width tell you whether a size is in the same family as what you have. They do not tell you whether 285/60R20 clears your fenders, matches your wheel width, or is load-rated for the vehicle. Check the door-jamb sticker and the wheel well before you buy.
Speedometer and revs
At 603 revolutions per mile, a trip computer calibrated for 285/60R20 is reading true only while this diameter is on the truck. A taller replacement under-reads speed and distance by the same percent the diameter grew. A shorter one over-reads. The comparison calculator puts a second size next to 285/60R20 and shows the error at 60 mph.