275/65R18 tire size
A 275/65R18 tire is 32.1 inches (815 mm) tall and 10.8 inches (275 mm) wide, for a 18-inch wheel. Each sidewall is 7.0 inches (179 mm), 65% of the width, and the tire makes about 629 revolutions a mile.
Sources checked
| Dimension | 275/65R18 |
|---|---|
| Overall diameter | 32.07 in (815 mm) |
| Section width | 10.83 in (275 mm) |
| Sidewall height | 7.04 in (179 mm) |
| Aspect ratio | 65% |
| Rim diameter | 18 in |
| Circumference | 100.8 in (2,559 mm) |
| Revolutions per mile | 629 |
| Revolutions per km | 391 |
Compare 275/65R18 with another size
Metric, LT and flotation
At 60 mph on the speedometer you’re doing
62.0mph
+3.4% · the speedometer reads low
- Height
- +1.08 in (+28 mm)
- Width
- 0.00 in (0 mm)
- Ground clearance
- +0.54 in (+14 mm)
- Each side, same wheel
- 0.00 in (0 mm)
275/65R18 and 275/70R18 side by side
| Dimension | 275/65R18 | 275/70R18 | Change |
|---|---|---|---|
| Overall diameter | 32.07 in (815 mm) | 33.16 in (842 mm) | +1.09 in (+27 mm) |
| Section width | 10.83 in (275 mm) | 10.83 in (275 mm) | 0.00 in (0 mm) |
| Sidewall height | 7.04 in (179 mm) | 7.58 in (193 mm) | +0.54 in (+14 mm) |
| Aspect ratio | 65% | 70% | |
| Rim diameter | 18 in | 18 in | |
| Circumference | 100.8 in | 104.2 in | +3.4 in |
| Revolutions per mile | 629 | 608 | −21 |
| Revolutions per km | 391 | 378 | −13 |
The working
- 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.
- 275/70R18: sidewall = 275 mm × 70% = 192.5 mm = 7.58 in.
- Diameter = rim + 2 × sidewall = 18 + 2 × 7.58 = 33.16 in (842 mm).
- Circumference = π × 33.16 = 104.2 in; revolutions per mile = 63,360 ÷ 104.2 = 608.
- Speedometer. True speed = what it shows × new diameter ÷ old = 60 × 33.16 ÷ 32.07 = 62.0 mph.
- Ground clearance. Half the change in diameter: (33.16 − 32.07) ÷ 2 = +0.54 in.
Where the 275/65R18 numbers come from
The section width is 275 mm (10.83 inches), and each sidewall is 65% of it: 178.8 mm, or 7.04 inches. Two sidewalls and the 18-inch rim make 32.07 inches (815 mm).
One turn covers π × 32.07 = 100.8 inches, so the tire turns 629 times a mile and 391 times a kilometer.
What tire makers publish for 275/65R18
Inflated on the maker’s measuring rim. The percentage is the printed diameter against the 32.07 inches worked out above.
| Tire | Size as printed | Diameter | Width | Revs per mile |
|---|---|---|---|---|
| Toyo Open Country A/T III | 275/65R18 | 32.1 in (+0.1%) | 11 in | 647 |
| Toyo Open Country A/T III, outlined white letters | LT275/65R18 | 32.3 in (+0.7%) | 11 in | 643 |
| Toyo Open Country A/T III, black sidewall | LT275/65R18 | 32.1 in (+0.1%) | 11 in | 647 |
Other 18-inch sizes against 275/65R18
Each size’s height against 275/65R18, and what a speedometer set for 275/65R18 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 | −21.8% | 46.9 mph |
| 225/45R18 | 26.0 in | 8.9 in | −19.0% | 48.6 mph |
| 225/55R18 | 27.7 in | 8.9 in | −13.5% | 51.9 mph |
| 225/60R18 | 28.6 in | 8.9 in | −10.7% | 53.6 mph |
| 235/45R18 | 26.3 in | 9.3 in | −17.9% | 49.2 mph |
| 235/50R18 | 27.3 in | 9.3 in | −15.0% | 51.0 mph |
| 235/55R18 | 28.2 in | 9.3 in | −12.2% | 52.7 mph |
| 235/60R18 | 29.1 in | 9.3 in | −9.3% | 54.4 mph |
| 235/65R18 | 30.0 in | 9.3 in | −6.4% | 56.2 mph |
| 245/40R18 | 25.7 in | 9.6 in | −19.8% | 48.1 mph |
| 245/45R18 | 26.7 in | 9.6 in | −16.8% | 49.9 mph |
| 245/60R18 | 29.6 in | 9.6 in | −7.8% | 55.3 mph |
| 255/55R18 | 29.0 in | 10.0 in | −9.5% | 54.3 mph |
| 255/70R18 | 32.1 in | 10.0 in | −0.1% | 60.0 mph |
| 265/60R18 | 30.5 in | 10.4 in | −4.8% | 57.1 mph |
| 265/65R18 compared | 31.6 in | 10.4 in | −1.6% | 59.0 mph |
| 265/70R18 | 32.6 in | 10.4 in | +1.7% | 61.0 mph |
| 275/70R18 compared | 33.2 in | 10.8 in | +3.4% | 62.0 mph |
| 285/65R18 compared | 32.6 in | 11.2 in | +1.6% | 61.0 mph |
| 35x12.50R18 | 35.0 in | 12.5 in | +9.1% | 65.5 mph |
275/65R18 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 275/65R18 in inches?
About 32.1x10.8R18: 32.1 inches tall and 10.8 inches wide on a 18-inch wheel, with 7.0-inch sidewalls. Exactly, 18 + 2 × 275 mm × 0.65 ÷ 25.4 = 32.07 inches.
How many revolutions per mile does a 275/65R18 make?
629 by its diameter: 63,360 inches in a mile ÷ 100.8 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 LT275/65R18 the same size as P275/65R18?
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.