Tire Ruler325/65R18 dimensions
| Overall diameter (height) | 34.63″ · 880 mm |
| Section width | 12.80″ · 325 mm |
| Sidewall height | 8.32″ · 211 mm |
| Wheel diameter | 18″ |
| Rim width (rule of thumb) | 9–11.5″ |
| Circumference | 108.8″ |
| Revolutions per mile | 582 |
| In inches (flotation style) | 34.6 × 12.8R18 |
How it’s calculated: the sidewall is 65% of the 325 mm width = 211.3 mm (8.32″). Add two sidewalls to the 18″ wheel: 18 + 2 × 8.32 = 34.63″.
Bigger tires than 325/65R18 on 18″ wheels
| Size | Height | Taller by | 60 mph reads |
|---|---|---|---|
| 35x12.50R18 | 35.0″ | +0.37″ (+1.1%) | 60.6 mph |
| 37x12.50R18 | 37.0″ | +2.37″ (+6.8%) | 64.1 mph |
“60 mph reads” is your real speed when a speedometer set up for 325/65R18 shows 60. Above about 3% taller, most trucks need a leveling kit or lift, and the speedometer should be recalibrated.
Sizes equivalent to 325/65R18
Within 1.5% of the same height on an 18″ wheel. Usually interchangeable for the speedometer; check width, load index and clearance.
| Size | Height | Width | Difference |
|---|---|---|---|
| 285/75R18 | 34.8″ | 11.2″ | +0.6% |
| 35x12.50R18 | 35.0″ | 12.5″ | +1.1% |
| 295/70R18 | 34.3″ | 11.6″ | −1.1% |
Same height on a different wheel size
Changing wheel size (plus or minus sizing) while keeping the overall height keeps your speedometer right:
- 35x12.50R15: 35.0″ tall on a 15″ wheel (+1.1%)
- 315/75R16: 34.6″ tall on a 16″ wheel (−0.1%)
- 315/70R17: 34.4″ tall on a 17″ wheel (−0.8%)
- 35x12.50R17: 35.0″ tall on a 17″ wheel (+1.1%)
- 285/65R20: 34.6″ tall on a 20″ wheel (−0.1%)
- 295/65R20: 35.1″ tall on a 20″ wheel (+1.3%)
- 35x12.50R20: 35.0″ tall on a 20″ wheel (+1.1%)
- 35x13.50R20: 35.0″ tall on a 20″ wheel (+1.1%)
- 35x12.50R22: 35.0″ tall on a 22″ wheel (+1.1%)
Popular 325/65R18 comparisons
Frequently asked questions
Is 325/65R18 a 35 inch tire?
Not quite. 325/65R18 is 34.63 inches tall, between a 34 and a 35 inch tire.
What size is 325/65R18 in inches?
325/65R18 is 34.6 inches tall (overall diameter), 12.8 inches wide, with a 8.3 inch sidewall, and fits an 18 inch wheel.
What tire size is equivalent to 325/65R18?
Sizes within 1.5% of the same diameter on an 18" wheel: 285/75R18 (34.8"), 35x12.50R18 (35.0"), 295/70R18 (34.3"). Check load index and width before swapping.
What rim width fits 325/65R18?
As a rule of thumb, about 9–11.5 inches. The tire maker's spec sheet lists the approved range for each model.
How many revolutions per mile does 325/65R18 make?
About 582 revolutions per mile in theory (circumference 108.8 in). Real tires turn slightly more because they flatten under load.