255/65R18 tire size: 31.05 in tall
Diameter, sidewall, width and revs per mile for 255/65R18, the common sizes within 3% of its diameter, and what each one does to the speedometer.
255/65R18, in short: 31.05 in (789 mm) tall and 255 mm (10.04 in) wide, with a 6.53 in (165.8 mm) sidewall, for a 18-inch wheel. Circumference is 97.55 in, so it turns about 650 times per mile (calculated from the nominal size).
Calculated from the size: sidewall = 255 × 65% = 165.75 mm; diameter = 2 × 6.526 in + 18 in; revs per mile = 63,360 ÷ (π × diameter).
Sizes within 3% of 255/65R18
17 common sizes come within ±3% of 31.05 in: 2 on the same 18-inch wheel, 5 plus-size and 10 minus-size. The last column is what the speedometer shows when the vehicle, set up for 255/65R18, is doing a true 60 mph.
| Size | Fit | Diameter | Difference | Width | Sidewall | Revs/mile (calc.) | Speedometer at a true 60 |
|---|---|---|---|---|---|---|---|
| 255/65R18 | This size | 31.05 in | - | 255 mm | 6.53 in | 650 | 60.0 mph |
| 245/75R16 | Minus 2 | 30.47 in | -1.88% | 245 mm | 7.23 in | 662 | 61.1 mph |
| 265/70R16 | Minus 2 | 30.61 in | -1.43% | 265 mm | 7.30 in | 659 | 60.9 mph |
| 265/75R16 | Minus 2 | 31.65 in | +1.93% | 265 mm | 7.82 in | 637 | 58.9 mph |
| 235/85R16 | Minus 2 | 31.73 in | +2.18% | 235 mm | 7.86 in | 636 | 58.7 mph |
| 245/70R17 | Minus 1 | 30.50 in | -1.76% | 245 mm | 6.75 in | 661 | 61.1 mph |
| 265/65R17 | Minus 1 | 30.56 in | -1.57% | 265 mm | 6.78 in | 660 | 61.0 mph |
| 255/70R17 | Minus 1 | 31.06 in | +0.01% | 255 mm | 7.03 in | 649 | 60.0 mph |
| 245/75R17 | Minus 1 | 31.47 in | +1.34% | 245 mm | 7.23 in | 641 | 59.2 mph |
| 265/70R17 | Minus 1 | 31.61 in | +1.79% | 265 mm | 7.30 in | 638 | 58.9 mph |
| 235/80R17 | Minus 1 | 31.80 in | +2.42% | 235 mm | 7.40 in | 634 | 58.6 mph |
| 265/60R18 | Same wheel | 30.52 in | -1.71% | 265 mm | 6.26 in | 661 | 61.0 mph |
| 265/65R18 | Same wheel | 31.56 in | +1.65% | 265 mm | 6.78 in | 639 | 59.0 mph |
| 235/55R20 | Plus 2 | 30.18 in | -2.81% | 235 mm | 5.09 in | 668 | 61.7 mph |
| 265/50R20 | Plus 2 | 30.43 in | -1.99% | 265 mm | 5.22 in | 663 | 61.2 mph |
| 255/55R20 | Plus 2 | 31.04 in | -0.03% | 255 mm | 5.52 in | 650 | 60.0 mph |
| 285/50R20 | Plus 2 | 31.22 in | +0.55% | 285 mm | 5.61 in | 646 | 59.7 mph |
| 275/55R20 | Plus 2 | 31.91 in | +2.76% | 275 mm | 5.95 in | 632 | 58.4 mph |
A taller tire makes the speedometer read low, a shorter one high. Plus-sizing keeps the diameter close by trading sidewall for wheel. Any replacement needs a load index at least as high as the vehicle's tire placard calls for, and a wheel width the tire is approved for.
255/65R18 compared
255/65R18 side by side with 265/65R18 and 255/55R20: dimension by dimension, and what the swap does to the speedometer.
255/65R18 vs 265/65R18
+1.65% diameter| 255/65R18 | 265/65R18 | Difference | |
|---|---|---|---|
| Overall diameter | 31.05 in | 31.56 in | +0.51 in (+1.6%) |
| Section width | 255 mm | 265 mm | +10 mm |
| Sidewall height | 6.53 in | 6.78 in | +0.26 in |
| Wheel diameter | 18 in | 18 in | +0 in |
| Circumference | 97.6 in | 99.2 in | +1.6 in |
| Revs per mile (calc.) | 650 | 639 | -11 |
265/65R18 is 1.6% taller than 255/65R18. At a true 60 mph the speedometer shows 59.0 mph (it reads low), and when it shows 60 you're doing 61.0 mph.
255/65R18 vs 255/55R20
-0.03% diameter| 255/65R18 | 255/55R20 | Difference | |
|---|---|---|---|
| Overall diameter | 31.05 in | 31.04 in | -0.01 in (-0.0%) |
| Section width | 255 mm | 255 mm | +0 mm |
| Sidewall height | 6.53 in | 5.52 in | -1.00 in |
| Wheel diameter | 18 in | 20 in | +2 in |
| Circumference | 97.6 in | 97.5 in | -0.0 in |
| Revs per mile (calc.) | 650 | 650 | +0 |
255/55R20 and 255/65R18 have the same diameter, so the speedometer doesn't change.
Which vehicles come with 255/65R18
Vehicles sold in the US that have 255/65R18 as the standard size on these trims, with the page that lists it. The tire placard on the driver's door edge or post has the size, and the load and inflation, for the exact vehicle.
- Ford Explorer 2025 model year · ActiveMavis Tire OE fitment page, 2025 Ford Explorer Active (size flagged standard 'S')
- Ford Explorer 2023 model year · Base, XLTMavis Tire OE fitment page, 2023 Ford Explorer XLT (size flagged standard 'S')
Vehicles mostly picked from Carscoops: 2025 U.S. car sales, full-year top 25 (Car and Driver data, January 2026).
Questions about 255/65R18 tires
How tall is a 255/65R18 tire?
What is 255/65R18 in inches?
How many revolutions per mile does a 255/65R18 tire make?
What size can replace 255/65R18?
255/65R18 vs 265/65R18: what's the difference?
Which vehicles come with 255/65R18 tires?
How these numbers are worked out
- NHTSA: Tire safety, everything rides on it (reading the sidewall and the placard)
- Tire Rack: How do I calculate tire dimensions?
- Jalopnik: What the 3% rule means for your tires (April 2026)
Checked October 2026. Dimensions are nominal, calculated from the size designation. A real tire's diameter, width and revs per mile vary by brand, tread depth, rim width and load, so check the maker's spec sheet.
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