What Size Is 33×12.50R20 Tires? | Real Dimensions Explained

A 33×12.50R20 tire is roughly 33 inches tall, 12.50 inches wide, and fits a 20-inch wheel.

If you’re shopping for bigger tires, the 33×12.50R20 size is a popular upgrade for trucks and SUVs. The markings tell you three things: the tire stands about 33 inches tall, measures 12.50 inches across the tread, and mounts on a 20-inch rim. The “R” means radial construction, and “LT” versions are light-truck rated for heavier loads.

But here’s what most listings don’t tell you: actual measurements vary by brand. Nitto’s Ridge Grappler in this size checks in at 32.76 inches in diameter, while Toyo’s Open Country A/T III runs slightly shorter at 32.5 inches. That half-inch difference matters for clearance and speedometer accuracy, so never assume all “33s” are identical.

Breaking Down The Tire Size Markings

Reading inch-format flotation sizes is different from decoding metric sizes like P265/70R17. The 33×12.50R20 format skips the aspect ratio entirely and states the height and width directly in inches.

• 33 – nominal overall diameter in inches (the tire’s height when mounted and inflated)
• 12.50 – section width in inches (widest point of the sidewall, not tread width)
• R – radial construction
• 20 – wheel diameter in inches the tire fits

One common mistake is treating this as a metric size. It isn’t — it’s an inch-format flotation size, and the numbers don’t convert the way metric sizes do.

What’s The Actual Diameter Of A 33×12.50R20?

Across tire brands, the real mounted diameter lands between 32.5 and 33.0 inches depending on the specific model. The generic size chart from tiresize.com’s 33X12.50R20 spec page lists a 33.0-inch diameter with 611 revolutions per mile, but manufacturers publish different figures for their own tires.

Load ratings and max pressure also vary by model, not by size alone. Here’s a quick look at real published specs:

Will 33 X 12.50 Fit Your Truck?

Mounting these tires requires a wheel between 8.5 and 11.0 inches wide — most listings spec a 10-inch measured rim. But the tire label alone doesn’t guarantee fitment. Clearance depends on wheel offset, suspension setup, and whether the tire rubs at full turn or under articulation. Leveling kits or lifts are often needed on stock trucks, and speedometer calibration becomes necessary since the larger diameter changes readings.

Variations Worth Knowing Before You Buy

Two tires both marked 33×12.50R20 can differ meaningfully in weight, tread depth, and load capacity. The Nitto Ridge Grappler in this size weighs 69.5 lb with 18.3/32-inch tread depth, while Toyo’s A/T III weighs 76 lb with shallower 16.9/32-inch tread. Those differences affect ride quality, fuel economy, and how the tire performs off-road.

If you’re comparing options for a purchase, our roundup of the best 33×12.50R20 tire models breaks down real-world tradeoffs across the top brands to help you match a set to your driving style and budget.

Also note that a 33×12.50R20 is not a direct equivalent to any metric size. While some metric tires are close in height, the 12.50-inch width and 20-inch wheel requirement make this a distinct fitment category.

FAQs

What does the “LT” in 33X12.50R20LT mean?

LT stands for light truck, indicating the tire is built for heavier vehicles like pickups and SUVs. LT tires have reinforced sidewalls and higher load capacities than passenger-car tires, which is why most 33-inch tires intended for trucks carry this designation.

How many revolutions per mile does a 33-inch tire make?

Most 33×12.50R20 tires make roughly 611 to 639 revolutions per mile depending on the brand and actual diameter. The Nitto Ridge Grappler and Toyo Open Country M/T both publish 634 revs/mile, while the Goodyear Wrangler MT/R shows 633. Smaller-diameter models turn more revolutions per mile.

Can I put 33×12.50R20 tires on a 20×9 wheel?

Yes, a 9-inch-wide wheel falls within the recommended 8.5 to 11.0-inch rim width range for this tire size. The tire’s section width of about 12.5 inches will appear slightly bulged but remains within safe mounting parameters. Always verify your specific wheel’s width rating and your vehicle’s clearance before mounting.