285/65R18 tire size
A 285/65R18 tire is 32.6 inches (828 mm) tall and 11.2 inches (285 mm) wide, for a 18-inch wheel. Each sidewall is 7.3 inches (185 mm), 65% of the width, and the tire makes about 619 revolutions a mile.
Sources checked
| Dimension | 285/65R18 |
|---|---|
| Overall diameter | 32.59 in (828 mm) |
| Section width | 11.22 in (285 mm) |
| Sidewall height | 7.29 in (185 mm) |
| Aspect ratio | 65% |
| Rim diameter | 18 in |
| Circumference | 102.4 in (2,600 mm) |
| Revolutions per mile | 619 |
| Revolutions per km | 385 |
Compare 285/65R18 with another size
Metric, LT and flotation
At 60 mph on the speedometer you’re doing
59.1mph
−1.6% · the speedometer reads high
- Height
- −0.51 in (−13 mm)
- Width
- −0.39 in (−10 mm)
- Ground clearance
- −0.26 in (−7 mm)
- Each side, same wheel
- −0.20 in (−5 mm)
285/65R18 and 275/65R18 side by side
| Dimension | 285/65R18 | 275/65R18 | Change |
|---|---|---|---|
| Overall diameter | 32.59 in (828 mm) | 32.07 in (815 mm) | −0.52 in (−13 mm) |
| Section width | 11.22 in (285 mm) | 10.83 in (275 mm) | −0.39 in (−10 mm) |
| Sidewall height | 7.29 in (185 mm) | 7.04 in (179 mm) | −0.25 in (−6 mm) |
| Aspect ratio | 65% | 65% | |
| Rim diameter | 18 in | 18 in | |
| Circumference | 102.4 in | 100.8 in | −1.6 in |
| Revolutions per mile | 619 | 629 | +10 |
| Revolutions per km | 385 | 391 | +6 |
The working
- 285/65R18: sidewall = 285 mm × 65% = 185.3 mm = 7.29 in.
- Diameter = rim + 2 × sidewall = 18 + 2 × 7.29 = 32.59 in (828 mm).
- Circumference = π × 32.59 = 102.4 in; revolutions per mile = 63,360 ÷ 102.4 = 619.
- 275/65R18: sidewall = 275 mm × 65% = 178.8 mm = 7.04 in.
- Diameter = rim + 2 × sidewall = 18 + 2 × 7.04 = 32.07 in (815 mm).
- Circumference = π × 32.07 = 100.8 in; revolutions per mile = 63,360 ÷ 100.8 = 629.
- Speedometer. True speed = what it shows × new diameter ÷ old = 60 × 32.07 ÷ 32.59 = 59.1 mph.
- Ground clearance. Half the change in diameter: (32.07 − 32.59) ÷ 2 = −0.26 in.
Where the 285/65R18 numbers come from
The section width is 285 mm (11.22 inches), and each sidewall is 65% of it: 185.3 mm, or 7.29 inches. Two sidewalls and the 18-inch rim make 32.59 inches (828 mm).
One turn covers π × 32.59 = 102.4 inches, so the tire turns 619 times a mile and 385 times a kilometer.
What tire makers publish for 285/65R18
Inflated on the maker’s measuring rim. The percentage is the printed diameter against the 32.59 inches worked out above.
| Tire | Size as printed | Diameter | Width | Revs per mile |
|---|---|---|---|---|
| Toyo Open Country A/T III | LT285/65R18 | 32.6 in (0.0%) | 11.5 in | 638 |
| Nitto Trail Grappler M/T | LT285/65R18 | 32.83 in (+0.7%) | 11.93 in | – |
Other 18-inch sizes against 285/65R18
Each size’s height against 285/65R18, and what a speedometer set for 285/65R18 shows at 60 mph with that size on.
| Size | Diameter | Width | Height change | At 60 mph shown |
|---|---|---|---|---|
| 225/40R18 | 25.1 in | 8.9 in | −23.0% | 46.2 mph |
| 225/45R18 | 26.0 in | 8.9 in | −20.3% | 47.8 mph |
| 225/55R18 | 27.7 in | 8.9 in | −14.9% | 51.1 mph |
| 225/60R18 | 28.6 in | 8.9 in | −12.1% | 52.7 mph |
| 235/45R18 | 26.3 in | 9.3 in | −19.2% | 48.5 mph |
| 235/50R18 | 27.3 in | 9.3 in | −16.4% | 50.2 mph |
| 235/55R18 | 28.2 in | 9.3 in | −13.5% | 51.9 mph |
| 235/60R18 | 29.1 in | 9.3 in | −10.7% | 53.6 mph |
| 235/65R18 | 30.0 in | 9.3 in | −7.9% | 55.3 mph |
| 245/40R18 | 25.7 in | 9.6 in | −21.1% | 47.4 mph |
| 245/45R18 | 26.7 in | 9.6 in | −18.1% | 49.1 mph |
| 245/60R18 | 29.6 in | 9.6 in | −9.2% | 54.5 mph |
| 255/55R18 | 29.0 in | 10.0 in | −10.9% | 53.5 mph |
| 255/70R18 | 32.1 in | 10.0 in | −1.6% | 59.0 mph |
| 265/60R18 | 30.5 in | 10.4 in | −6.3% | 56.2 mph |
| 265/65R18 | 31.6 in | 10.4 in | −3.1% | 58.1 mph |
| 265/70R18 | 32.6 in | 10.4 in | +0.1% | 60.0 mph |
| 275/65R18 compared | 32.1 in | 10.8 in | −1.6% | 59.1 mph |
| 275/70R18 | 33.2 in | 10.8 in | +1.8% | 61.1 mph |
| 35x12.50R18 | 35.0 in | 12.5 in | +7.4% | 64.4 mph |
285/65R18 compared
Every size: the tire size calculator. With the wheels off, the nuts go back on at your vehicle’s lug nut torque.
Questions
What is 285/65R18 in inches?
About 32.6x11.2R18: 32.6 inches tall and 11.2 inches wide on a 18-inch wheel, with 7.3-inch sidewalls. Exactly, 18 + 2 × 285 mm × 0.65 ÷ 25.4 = 32.59 inches.
How many revolutions per mile does a 285/65R18 make?
619 by its diameter: 63,360 inches in a mile ÷ 102.4 inches a turn. Tire makers’ published figures are measured under load, when the tire rolls on a slightly smaller radius, and run 2.8% to 3.3% higher in Toyo’s tables.
Is LT285/65R18 the same size as P285/65R18?
In dimensions, yes: the numbers mean the same in every metric size. The letters mark what the tire is built for, and an LT tire’s load is rated differently, so check the load index and pressure your vehicle needs before swapping one for the other.
Sources
- Bridgestone Americas: Determining tire size: P-metric, Euro-metric, LT-metric, C-type and flotation sizes, and what each number means (checked October 28, 2026)
- Toyo Tires: Extensa A/S II sizes and specifications: inflated overall diameter and width, revolutions per mile (checked October 28, 2026)
- Toyo Tires: Proxes Sport A/S sizes and specifications: inflated overall diameter and width, revolutions per mile (checked October 28, 2026)
- Toyo Tires: Open Country A/T III sizes and specifications: P-metric, LT-metric and flotation sizes, with revolutions per mile (checked October 28, 2026)
- Nitto Tire: Trail Grappler M/T sizes and specs: inflated overall diameter and width, LT-metric and flotation sizes (checked October 28, 2026)
Spotted a number that doesn’t match your manual or a source? Tell us; corrections are logged on the sources page.