225/55R18 tire size: 27.74 in tall
Diameter, sidewall, width and revs per mile for 225/55R18, the common sizes within 3% of its diameter, and what each one does to the speedometer.
225/55R18, in short: 27.74 in (705 mm) tall and 225 mm (8.86 in) wide, with a 4.87 in (123.8 mm) sidewall, for a 18-inch wheel. Circumference is 87.16 in, so it turns about 727 times per mile (calculated from the nominal size).
Calculated from the size: sidewall = 225 × 55% = 123.75 mm; diameter = 2 × 4.872 in + 18 in; revs per mile = 63,360 ÷ (π × diameter).
Sizes within 3% of 225/55R18
19 common sizes come within ±3% of 27.74 in: 3 on the same 18-inch wheel, 7 plus-size and 9 minus-size. The last column is what the speedometer shows when the vehicle, set up for 225/55R18, is doing a true 60 mph.
| Size | Fit | Diameter | Difference | Width | Sidewall | Revs/mile (calc.) | Speedometer at a true 60 |
|---|---|---|---|---|---|---|---|
| 225/55R18 | This size | 27.74 in | - | 225 mm | 4.87 in | 727 | 60.0 mph |
| 215/65R16 | Minus 2 | 27.00 in | -2.67% | 215 mm | 5.50 in | 747 | 61.6 mph |
| 215/70R16 | Minus 2 | 27.85 in | +0.38% | 215 mm | 5.93 in | 724 | 59.8 mph |
| 225/70R16 | Minus 2 | 28.40 in | +2.37% | 225 mm | 6.20 in | 710 | 58.6 mph |
| 215/60R17 | Minus 1 | 27.16 in | -2.11% | 215 mm | 5.08 in | 743 | 61.3 mph |
| 235/55R17 | Minus 1 | 27.18 in | -2.04% | 235 mm | 5.09 in | 742 | 61.3 mph |
| 225/60R17 | Minus 1 | 27.63 in | -0.41% | 225 mm | 5.31 in | 730 | 60.2 mph |
| 215/65R17 | Minus 1 | 28.00 in | +0.94% | 215 mm | 5.50 in | 720 | 59.4 mph |
| 235/60R17 | Minus 1 | 28.10 in | +1.29% | 235 mm | 5.55 in | 718 | 59.2 mph |
| 225/65R17 | Minus 1 | 28.52 in | +2.78% | 225 mm | 5.76 in | 707 | 58.4 mph |
| 235/50R18 | Same wheel | 27.25 in | -1.77% | 235 mm | 4.63 in | 740 | 61.1 mph |
| 215/55R18 | Same wheel | 27.31 in | -1.56% | 215 mm | 4.66 in | 738 | 61.0 mph |
| 235/55R18 | Same wheel | 28.18 in | +1.56% | 235 mm | 5.09 in | 716 | 59.1 mph |
| 255/40R19 | Plus 1 | 27.03 in | -2.57% | 255 mm | 4.02 in | 746 | 61.6 mph |
| 235/45R19 | Plus 1 | 27.33 in | -1.50% | 235 mm | 4.16 in | 738 | 60.9 mph |
| 245/45R19 | Plus 1 | 27.68 in | -0.23% | 245 mm | 4.34 in | 729 | 60.1 mph |
| 255/45R19 | Plus 1 | 28.04 in | +1.05% | 255 mm | 4.52 in | 719 | 59.4 mph |
| 235/50R19 | Plus 1 | 28.25 in | +1.83% | 235 mm | 4.63 in | 714 | 58.9 mph |
| 245/40R20 | Plus 2 | 27.72 in | -0.10% | 245 mm | 3.86 in | 728 | 60.1 mph |
| 255/40R20 | Plus 2 | 28.03 in | +1.04% | 255 mm | 4.02 in | 719 | 59.4 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.
225/55R18 compared
225/55R18 side by side with 225/60R18 and 235/55R18: dimension by dimension, and what the swap does to the speedometer.
225/55R18 vs 225/60R18
+3.19% diameter| 225/55R18 | 225/60R18 | Difference | |
|---|---|---|---|
| Overall diameter | 27.74 in | 28.63 in | +0.89 in (+3.2%) |
| Section width | 225 mm | 225 mm | +0 mm |
| Sidewall height | 4.87 in | 5.31 in | +0.44 in |
| Wheel diameter | 18 in | 18 in | +0 in |
| Circumference | 87.2 in | 89.9 in | +2.8 in |
| Revs per mile (calc.) | 727 | 704 | -22 |
225/60R18 is 3.2% taller than 225/55R18. At a true 60 mph the speedometer shows 58.1 mph (it reads low), and when it shows 60 you're doing 61.9 mph.
225/55R18 vs 235/55R18
+1.56% diameter| 225/55R18 | 235/55R18 | Difference | |
|---|---|---|---|
| Overall diameter | 27.74 in | 28.18 in | +0.43 in (+1.6%) |
| Section width | 225 mm | 235 mm | +10 mm |
| Sidewall height | 4.87 in | 5.09 in | +0.22 in |
| Wheel diameter | 18 in | 18 in | +0 in |
| Circumference | 87.2 in | 88.5 in | +1.4 in |
| Revs per mile (calc.) | 727 | 716 | -11 |
235/55R18 is 1.6% taller than 225/55R18. At a true 60 mph the speedometer shows 59.1 mph (it reads low), and when it shows 60 you're doing 60.9 mph.
Which vehicles come with 225/55R18
Vehicles sold in the US that have 225/55R18 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.
- Subaru Crosstrek 2025 model year · Sport, LimitedMavis Tire OE fitment page, 2025 Subaru Crosstrek Sport (size flagged standard 'S')
- Subaru Forester 2025 model year · Limited (2024: Sport, Limited, Touring)Mavis Tire OE fitment page, 2025 Subaru Forester Limited (size flagged standard 'S')
- Chevrolet Trax 2025 model year · ACTIV, 1RSMavis Tire OE fitment page, 2025 Chevrolet Trax ACTIV (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 225/55R18 tires
How tall is a 225/55R18 tire?
What is 225/55R18 in inches?
How many revolutions per mile does a 225/55R18 tire make?
What size can replace 225/55R18?
225/55R18 vs 225/60R18: what's the difference?
Which vehicles come with 225/55R18 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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