245/60R18 Tire Size Explained: What the Numbers Mean in Inches

A 245/60R18 tire is about 9.6 inches wide, has a 5.8-inch sidewall, and stands roughly 29.6 inches tall on an 18-inch wheel.

A tire sidewall looks like a code because it is one — each group of digits describes a different physical dimension, and reading them wrong shifts every measurement you calculate afterward. The string 245/60R18 breaks into four parts: width, aspect ratio, construction type, and wheel diameter. Get those four right and you can size a replacement, compare against a different tire, or check whether a set will clear your fenders — all without a measuring tape.

Breaking Down Each Number

Each figure in 245/60R18 measures something different, and mixing them up is the most common way people misread a tire. Here is what every character actually stands for.

• 245 — section width in millimeters, the tire’s widest point from sidewall to sidewall, roughly 9.6 inches.
• 60 — aspect ratio, meaning the sidewall height is 60% of the section width, not 60 of anything else.
• R — radial construction, the standard build for passenger tires today.
• 18 — wheel diameter in inches, so this tire mounts on an 18-inch rim.

The 245 is a width in millimeters, not a tread measurement. Tread width is a separate figure that manufacturers publish independently, and it always comes in a bit narrower than the section width.

What 245/60R18 Measures In Inches

Converting the metric figures gives a tire roughly 29.6 inches tall and 9.6 inches wide, with a 5.8-inch sidewall. That overall diameter comes from adding the wheel to two sidewalls: 18 inches plus 5.8 inches twice.

The math is straightforward once you have the pieces. Section width converts at 25.4 millimeters per inch, so 245 mm lands at about 9.6 inches. Sidewall height is 60% of 245 mm, or about 147 mm — roughly 5.8 inches. Double that, add the 18-inch wheel, and the tire stands about 29.6 inches tall, or 751 mm. The circumference works out to about 92.9 inches, and the tire turns roughly 682 times per mile.

Common Mistakes Drivers Make

The three biggest misreads are treating 245 as tread width, reading 60 as inches, and assuming 18 is the tire’s width. All three throw off size comparisons and can lead you to buy a set that doesn’t match.

Section width and tread width are not the same thing — the first is the tire’s widest bulge, the second is the part touching the road. That 60 is a percentage, so it only means anything in relation to the 245. And 18 tells you the wheel, not the tire body.

One more thing worth knowing before you order: actual dimensions vary slightly by brand and model. Two tires both stamped 245/60R18 can differ a few tenths of an inch in real-world diameter depending on mold, tread depth, and inflation. If you’re shopping for a set, a tested roundup of popular 245/60R18 tires worth buying saves a lot of guessing about which models actually deliver the size they advertise.

Fitment And Safety Checks Before You Buy

A tire built for an 18-inch wheel should only go on an 18-inch wheel, and the wheel itself should fall within the 7.0–8.5 inch rim-width range this size expects. Mounting on the wrong rim diameter isn’t a tight fit — it’s unsafe.

Wheel width matters as much as diameter. A 245/60R18 on a rim narrower or wider than that range will wear unevenly and handle poorly, even if it technically seats. Beyond the wheel, exact fit depends on the vehicle: load rating, brake clearance, suspension travel, and the manufacturer’s approved tire size list all play a role.

Changing to this size from a different one has ripple effects too. Because it stands about 29.6 inches tall, a smaller or larger substitute shifts your speedometer reading, gearing, and clearance. Your speedo could read low at highway speeds, and the tire might rub on a lowered suspension or tight wheel well. If you’re switching from a factory size, check the door jamb sticker before committing. Tire Size publishes a full 245/60R18 size specification if you want to cross-check the numbers against a specific model.