275/65R20 measures 34.1″ overall diameter and 10.8″ section width. Sidewall height is 7.0″, circumference is 107.0″, and the tire turns 592 times per mile. Those figures are geometry off the stamped size, not a brand or load range.
275/65R20 dimensions
| Measurement | Inches | Metric |
|---|---|---|
| Overall diameter | 34.1″ | 865 mm |
| Section width | 10.8″ | 275 mm |
| Sidewall height | 7.0″ | 179 mm |
| Circumference | 107.0″ | 2719 mm |
| Revolutions per mile | 592 | 368 / km |
The stamped width is 275 mm (10.8″). The aspect ratio is 65, so the sidewall is 65% of that width, which is 7.0″. The rim is 20 inches. Overall diameter is the rim plus two sidewalls: 20 + 2 × 7.0″ = 34.1″.
Sizes near 275/65R20
A swap that stays inside about 3% diameter usually keeps the speedometer honest and clears the same well. 295/60R20 is a close neighbour at -0.4% diameter. The percent column opens both stamps in the comparison calculator.
| Size | Diameter | Width | vs 275/65R20 |
|---|---|---|---|
| 295/60R20 | 33.9″ | 11.6″ | -0.4% |
| 285/65R20 | 34.6″ | 11.2″ | +1.5% |
| 305/75R16 | 34.0″ | 12.0″ | -0.2% |
| 285/60R20 | 33.5″ | 11.2″ | -1.8% |
| 285/75R17 | 33.8″ | 11.2″ | -0.7% |
| 275/80R17 | 34.3″ | 10.8″ | +0.7% |
How to read the stamped size
275/65R20 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 275/65R20 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 592 revolutions per mile, a trip computer calibrated for 275/65R20 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 275/65R20 and shows the error at 60 mph.