275/55R20 tire size
A 275/55R20 tire is 31.9 inches (810 mm) tall and 10.8 inches (275 mm) wide, for a 20-inch wheel. Each sidewall is 6.0 inches (151 mm), 55% of the width, and the tire makes about 632 revolutions a mile.
Sources checked
| Dimension | 275/55R20 |
|---|---|
| Overall diameter | 31.91 in (810 mm) |
| Section width | 10.83 in (275 mm) |
| Sidewall height | 5.95 in (151 mm) |
| Aspect ratio | 55% |
| Rim diameter | 20 in |
| Circumference | 100.2 in (2,546 mm) |
| Revolutions per mile | 632 |
| Revolutions per km | 393 |
Compare 275/55R20 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)
275/55R20 and 275/60R20 side by side
| Dimension | 275/55R20 | 275/60R20 | Change |
|---|---|---|---|
| Overall diameter | 31.91 in (810 mm) | 32.99 in (838 mm) | +1.08 in (+28 mm) |
| Section width | 10.83 in (275 mm) | 10.83 in (275 mm) | 0.00 in (0 mm) |
| Sidewall height | 5.95 in (151 mm) | 6.50 in (165 mm) | +0.55 in (+14 mm) |
| Aspect ratio | 55% | 60% | |
| Rim diameter | 20 in | 20 in | |
| Circumference | 100.2 in | 103.6 in | +3.4 in |
| Revolutions per mile | 632 | 611 | −21 |
| Revolutions per km | 393 | 380 | −13 |
The working
- 275/55R20: sidewall = 275 mm × 55% = 151.3 mm = 5.95 in.
- Diameter = rim + 2 × sidewall = 20 + 2 × 5.95 = 31.91 in (810 mm).
- Circumference = π × 31.91 = 100.2 in; revolutions per mile = 63,360 ÷ 100.2 = 632.
- 275/60R20: sidewall = 275 mm × 60% = 165.0 mm = 6.50 in.
- Diameter = rim + 2 × sidewall = 20 + 2 × 6.50 = 32.99 in (838 mm).
- Circumference = π × 32.99 = 103.6 in; revolutions per mile = 63,360 ÷ 103.6 = 611.
- Speedometer. True speed = what it shows × new diameter ÷ old = 60 × 32.99 ÷ 31.91 = 62.0 mph.
- Ground clearance. Half the change in diameter: (32.99 − 31.91) ÷ 2 = +0.54 in.
Where the 275/55R20 numbers come from
The section width is 275 mm (10.83 inches), and each sidewall is 55% of it: 151.3 mm, or 5.95 inches. Two sidewalls and the 20-inch rim make 31.91 inches (810 mm).
One turn covers π × 31.91 = 100.2 inches, so the tire turns 632 times a mile and 393 times a kilometer.
What tire makers publish for 275/55R20
Inflated on the maker’s measuring rim. The percentage is the printed diameter against the 31.91 inches worked out above.
| Tire | Size as printed | Diameter | Width | Revs per mile |
|---|---|---|---|---|
| Toyo Open Country A/T III | 275/55R20 | 31.9 in (0.0%) | 11.2 in | 651 |
| Toyo Open Country A/T III | LT275/55R20 | 31.9 in (0.0%) | 11.2 in | 651 |
Other 20-inch sizes against 275/55R20
Each size’s height against 275/55R20, and what a speedometer set for 275/55R20 shows at 60 mph with that size on.
| Size | Diameter | Width | Height change | At 60 mph shown |
|---|---|---|---|---|
| 245/50R20 | 29.6 in | 9.6 in | −7.1% | 55.7 mph |
| 255/50R20 | 30.0 in | 10.0 in | −5.9% | 56.5 mph |
| 255/55R20 | 31.0 in | 10.0 in | −2.7% | 58.4 mph |
| 275/60R20 compared | 33.0 in | 10.8 in | +3.4% | 62.0 mph |
| 275/65R20 | 34.1 in | 10.8 in | +6.8% | 64.1 mph |
| 285/55R20 compared | 32.3 in | 11.2 in | +1.4% | 60.8 mph |
| 285/60R20 | 33.5 in | 11.2 in | +4.9% | 62.9 mph |
| 33x12.50R20 | 33.0 in | 12.5 in | +3.4% | 62.1 mph |
| 35x12.50R20 | 35.0 in | 12.5 in | +9.7% | 65.8 mph |
275/55R20 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 275/55R20 in inches?
About 31.9x10.8R20: 31.9 inches tall and 10.8 inches wide on a 20-inch wheel, with 6.0-inch sidewalls. Exactly, 20 + 2 × 275 mm × 0.55 ÷ 25.4 = 31.91 inches.
How many revolutions per mile does a 275/55R20 make?
632 by its diameter: 63,360 inches in a mile ÷ 100.2 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 LT275/55R20 the same size as P275/55R20?
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.