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33×12.50R18 measures roughly 33 inches tall and 12.50 inches wide, and its closest metric equivalent is 305/60R18.
For the full breakdown, see our best 33×12.50R18 Tires guide.
Tire sizing is full of approximations, and what 33×12.50R18 is in metric terms depends on which dimension you’re trying to match. The closest metric equivalent, per tire-size conversion tables, is 305/60R18 — the size that comes nearest to this standard’s 33-inch diameter, 12.50-inch section width, and 18-inch rim.
If you’re comparing tires across measurement systems, planning a new set for a truck or SUV, or just decoding the numbers on your sidewall, the breakdown below covers what each figure means and which metric size actually fits your goal.
What Do the Numbers Mean?
33×12.50R18 breaks down into three measurements: a 33.0-inch overall diameter, a 12.50-inch section width, and an 18-inch wheel diameter. This inch-based format, called flotation sizing, still dominates off-road catalogs, while most factory tires use metric labels. That makes the size a staple for lifted trucks and off-road builds chasing extra ground clearance.
- 33 — approximate overall diameter in inches. Most 33×12.50R18 tires measure about 33.0 inches new, though the exact figure varies by brand, tread design, and wear.
- 12.50 — section width in inches, measured at the widest point of the sidewalls rather than across the tread.
- R18 — radial construction on an 18-inch wheel.
Two practical notes follow. Section width is not tread width, so a 12.50-inch tire can still have a noticeably narrower contact patch. And mounted width shifts slightly with rim width, which is one reason the same size can look different on two trucks.
The Closest Metric Equivalent to 33×12.50R18
The closest metric equivalent to 33×12.50R18 is 305/60R18, according to tire-size conversion tables. Two other sizes, 295/65R18 and 305/65R18, are commonly listed as practical alternatives when the goal is matching diameter, width, or both more closely.
Reading a metric size is straightforward once you know the code: 305 is the section width in millimeters, 60 is the aspect ratio (sidewall height as a percentage of width), R means radial, and 18 is the rim diameter.