275/65R18 tire size in inches and millimeters
275/65R18 measures 32.07 inches in overall diameter, 10.83 inches in section width, with a 7.04 inch sidewall.
Every dimension
| Size | In inches | In millimetres |
|---|---|---|
| Overall diameter | 32.07 in | 814.7 mm |
| Section width | 10.83 in | 275 mm |
| Sidewall height | 7.04 in | 178.8 mm |
| Circumference | 100.77 in | 2,559.5 mm |
| Revolutions per mile | 628.8 per mile | 390.7 per km |
Sizes that fit the same wheel
These sizes share a 18 inch wheel diameter and sit within 3% of 275/65R18 in overall diameter, which is the range a swap stays inside without recalibrating anything.
The percentage difference in overall diameter is the speedometer error: a tire 2% taller makes an indicated 60 mph a true 61.2 mph. They are the same number, so it is shown once.
| Alternate size | Overall diameter | Difference (in) | Difference (%) | Width difference (in) |
|---|---|---|---|---|
| 325/55R18 | 32.07 | 0.00 | 0.00 | 1.97 |
| 255/70R18 | 32.06 | -0.02 | -0.06 | -0.79 |
| 225/80R18 | 32.17 | 0.10 | 0.31 | -1.97 |
| 355/50R18 | 31.98 | -0.10 | -0.31 | 3.15 |
| 295/60R18 | 31.94 | -0.14 | -0.43 | 0.79 |
| 235/75R18 | 31.88 | -0.20 | -0.61 | -1.57 |
| 215/85R18 | 32.39 | 0.32 | 0.98 | -2.36 |
| 305/60R18 | 32.41 | 0.33 | 1.04 | 1.18 |
| 205/85R18 | 31.72 | -0.35 | -1.10 | -2.76 |
| 245/75R18 | 32.47 | 0.39 | 1.23 | -1.18 |
| 315/55R18 | 31.64 | -0.43 | -1.35 | 1.57 |
| 335/55R18 | 32.51 | 0.43 | 1.35 | 2.36 |
| 345/50R18 | 31.58 | -0.49 | -1.53 | 2.76 |
| 265/65R18 | 31.56 | -0.51 | -1.60 | -0.39 |
| 285/65R18 | 32.59 | 0.51 | 1.60 | 0.39 |
| 215/80R18 | 31.54 | -0.53 | -1.66 | -2.36 |
| 265/70R18 | 32.61 | 0.53 | 1.66 | -0.39 |
| 245/70R18 | 31.50 | -0.57 | -1.78 | -1.18 |
| 285/60R18 | 31.46 | -0.61 | -1.90 | 0.39 |
| 235/80R18 | 32.80 | 0.73 | 2.27 | -1.57 |
| 225/75R18 | 31.29 | -0.79 | -2.45 | -1.97 |
| 315/60R18 | 32.88 | 0.81 | 2.52 | 1.57 |
| 305/55R18 | 31.21 | -0.87 | -2.70 | 1.18 |
| 345/55R18 | 32.94 | 0.87 | 2.70 | 2.76 |
| 335/50R18 | 31.19 | -0.89 | -2.76 | 2.36 |
How this is worked out
sidewall height in millimetres = section width × aspect ratio ÷ 100
overall diameter in inches = wheel diameter + (section width × aspect ratio × 2) ÷ 2540
section width in inches = section width in millimetres ÷ 25.4
circumference in inches = π × overall diameter
revolutions per mile = 63360 ÷ circumference in inches
The divisor is 2540, not the 2550 some converters publish. Two sidewalls in inches are 2 × width × aspect ÷ (100 × 25.4), and the rounding costs about 0.07 inches at 34 inches.
For 275/65R18: the sidewall is 178.8 millimetres, two of them are 14.07 inches, and adding the 18 inch wheel gives 32.07 inches overall.
Questions
What size is 275/65R18 in inches?
32.07 inches in overall diameter, 10.83 inches in section width, with a 7.04 inch sidewall.
How tall is a 275/65R18 tire?
32.07 inches, which is 814.7 millimetres.
What do the numbers in 275/65R18 mean?
275 is the section width in millimetres, 65 is the sidewall height as a percentage of that width, and 18 is the wheel diameter in inches. Overall diameter is the wheel diameter plus two sidewalls: 32.07 inches.
Does 275/65R18 fit a 18-inch wheel?
Yes — the 18 in a metric tire size *is* the wheel diameter, so 275/65R18 is made for a 18 inch wheel. Rim width is a separate question the sidewall code does not answer.
What tire sizes are equivalent to 275/65R18?
325/55R18, 255/70R18, 225/80R18 are the closest by overall diameter, all on the same 18 inch wheel.
Fitting a size is not only a matter of diameter. Rim width, load rating, speed rating and clearance all decide whether a size works on a given vehicle, and none of them can be read off the sidewall code alone.