How Tall Are 285/70R18 Tires? 285/70R18 Tire Size Explained

A 285/70R18 tire measures about 33.7 inches tall, with an 11.2-inch section width, a 7.9-inch sidewall, and an 18-inch wheel diameter.

The number stamped on your sidewall isn’t a guess about how big the tire looks—it’s a set of three measurements that math can turn into exact inches. A 285/70R18 is what most shoppers call a “33-inch” tire, though it actually tapes out just past 33.5 inches. Knowing the real numbers matters the moment you check fender clearance or match a spare.

Here are the dimensions everyone’s asking about, followed by how they’re calculated and what the numbers don’t tell you.

What The Numbers In 285/70R18 Actually Mean

The code breaks into three parts: 285 is the section width in millimeters, 70 is the aspect ratio (sidewall height as a percentage of width), and 18 is the rim diameter in inches. It’s a metric size, which is why the width is millimeters while the wheel is inches.

The math works simply. Multiply 285 mm by 0.70 to get 199.5 mm of sidewall, convert that to inches (about 7.9), then add two sidewalls to the 18-inch rim. That gives you roughly 33.7 inches of total height. Some calculators express the same tire in flotation format as 33.7×11.2R18.

285/70R18 Size Breakdown

The circumference and revs-per-mile figures matter if you’re recalibrating a speedometer after a lift. A taller tire turns fewer times per mile, which is why your dash reads slow until you correct it. If you’re ready to compare actual models, this roundup of tested 285 70r18 all terrain tires breaks down real-world options.

Why Your Tire May Not Measure Exactly 33.7 Inches

Published dimensions are nominal, not gospel. Actual mounted height shifts with brand, model, load range, and inflation pressure. A load-range E tire pumped to 80 psi can sit noticeably taller than the same size at 35 psi, and tread depth changes things too.

This is why two 285/70R18 tires from different makers can differ by a quarter-inch or more. Always verify against the specific product listing rather than assuming every tire in this size is identical. BFGoodrich, for instance, lists its All-Terrain T/A KO3 LT285/70R18 at 33.7 inches in diameter but 11.5 inches in width—wider than the nominal 11.2-inch figure for the size class. tiresize.com’s KO3 listing shows those model-specific numbers alongside the measured rim width and load specs.

Rim-width guidance isn’t uniform either. One reference lists 7.5–9.5 inches as the approved wheel range for 285/70R18, while another fitment source spreads it to 8.5–10.5 inches. Published ranges differ, so check your specific wheel before buying.

What The Size Alone Doesn’t Tell You

Tire size defines nominal dimensions—not fitment. Whether a 285/70R18 clears your truck depends on wheel offset, suspension travel, fender clearance, and brake-caliper room. None of that comes from the sidewall number. The safest path is confirming fitment with your vehicle’s specs or a tire shop before purchase.

Load rating matters just as much. LT-metric versions like LT285/70R18 carry heavier construction and higher load capacity than passenger-metric equivalents. Match the load index and speed rating to your vehicle’s requirements—not just the size.