What Size Are 37 Inch Tires? | True Specs Explained

A 37-inch off-road tire is usually about 36.5 to 37 inches tall, around 12.5 inches wide, and built for 17- to 20-inch rims.

People ask this question because “37-inch tire” sounds simple. The catch is that the number on the sidewall is only part of the story. A 37-inch tire is sold as a height class, not a promise that every brand will measure a dead-on 37.00 inches once it’s mounted, aired up, and carrying weight.

That’s why two tires with “37” on the sidewall can fit a truck a little differently. One may stand closer to 36.7 inches, another may brush 36.9, and a wider version may need more room at full lock. Rim diameter matters too. A 37×12.50R17 and a 37×12.50R20 are both in the same height class, but the sidewall shape, ride feel, and wheel choice are not the same.

If you’re trying to pick the right setup for a Jeep, pickup, or trail rig, here’s the plain answer: most 37-inch tires land near 37 inches tall, 12.5 to 13.5 inches wide, and fit 17-, 18-, or 20-inch wheels. The smart move is to read the full size code, then check the brand’s spec sheet before you buy.

What Size Are 37 Inch Tires? The Numbers That Matter

When you see a size like 37×12.50R17, each part tells you one thing:

• 37 = the advertised overall diameter in inches
• 12.50 = the tire’s advertised section width in inches
• R17 = radial tire built for a 17-inch wheel

So, in day-to-day terms, a 37-inch tire is not one fixed measurement. It’s a family of tall light-truck tires that sit around the 37-inch mark. Width can change. Rim size can change. Load range, tread design, and brand-to-brand casing shape can change too.

That last part matters more than many buyers expect. Mud-terrain tires with big shoulder lugs can take up more room than an all-terrain in the same labeled size. A tire that measures a hair shorter on paper can still rub harder because the tread blocks stick farther into the wheel well.

37-Inch Tire Measurements On Real Sidewalls

You’ll run into two common ways these tires are labeled: flotation sizing and metric sizing. Flotation is the old-school off-road format. Metric is the modern light-truck format. Both can point you toward a tire that lives in the 37-inch zone.

Flotation Sizing

A size such as 37×12.50R17 is easy to read at a glance. It tells you the target height, the target width, and the wheel diameter. That’s why it’s so common on lifted trucks and Jeeps. You can spot the basics in one second.

Metric Sizing

A metric size such as LT315/80R17 gets more technical. The 315 is the section width in millimeters. The 80 is the aspect ratio, which sets the sidewall height as a share of the width. The R17 still means a 17-inch wheel. In practice, LT315/80R17 lands close to a 37×12.50R17, though the shape is a little narrower and taller in the sidewall math.

If you want a clean breakdown of the markings, BFGoodrich’s sidewall size breakdown lays out how width, ratio, and wheel numbers are read. NHTSA’s tire size advice also points drivers back to the door-jamb placard and owner’s manual before changing sizes.

Here’s what common 37-inch sizes usually look like in the real world. These numbers can shift a bit by brand and tread pattern, though they show the range most buyers will see on spec sheets.

Size Marking	What It Means	Usual Mounted Diameter
37×12.50R17	37-inch class, 12.5-inch width, 17-inch wheel	About 36.7 to 36.9 in.
37×13.50R17	Wider 37 on a 17-inch wheel	About 36.8 to 37.0 in.
37×12.50R18	Same height class on an 18-inch wheel	About 36.7 to 36.9 in.
37×13.50R18	Wider 37 on an 18-inch wheel	About 36.8 to 37.0 in.
37×12.50R20	37-inch class on a 20-inch wheel	About 36.7 to 36.9 in.
37×13.50R20	Wider 37 on a 20-inch wheel	About 36.8 to 37.0 in.
LT315/80R17	Metric near-match to a 37×12.50R17	About 36.8 in.

The big takeaway from that table is simple: “37” tells you the neighborhood, not the exact tape-measure reading. If you’re tight on clearance, even a few tenths of an inch can decide whether the tire clears your bumper, pinch weld, or control arm.

What Changes When You Step Up To 37s

Buying a 37 is not only about tire height. It changes the whole package around the wheel opening. That’s why people who jump from 33s or 35s to 37s often talk about more than ride height.

Clearance Gets Tight Fast

A 37-inch tire brings more radius and more section width, so rubbing can show up in places you didn’t expect. The usual trouble spots are the front bumper edge, fender liner, sway bar, pinch weld, and rear of the front wheel well when the steering is cranked. Wheel offset can make that better or worse.

This is also where width choice matters. A 37×12.50 tire is easier to package than a 37×13.50. The wider tire may look fuller, but it can swing a wider arc at lock and stuff harder into the body at compression.

Gearing And Speed Readings Shift

Taller tires change your effective gearing. The truck feels longer-legged, which sounds nice until the extra rotating weight and taller ratio dull the launch, soften braking feel, and add more hunting on hills. If you move from a true 35-inch tire to a true 37-inch tire, the jump is about 5.7 percent in diameter. Your speedometer can read low unless the truck is recalibrated.

Wheel Specs Still Matter

People sometimes lock onto the “37” and ignore the wheel. That’s a mistake. The rim diameter has to match the tire, and the rim width has to fall inside the approved range for that model. Many 37×12.50 tires are happiest around an 8.5- to 10-inch wheel, while wider 37s can want more rim. Backspacing and offset shape the fit just as much as lift height does.

Area To Check	What To Measure	What Often Changes With 37s
Suspension Height	Stuffed and full-lock clearance	Leveling kit or lift is often needed
Wheel Fitment	Width, offset, and backspacing	Rubbing can move from one spot to another
Axle Gearing	Current gear ratio and engine torque	Launch gets softer and downshifts rise
Speedometer	GPS speed versus dash reading	Dash speed can read lower than road speed
Brakes And Steering	Tire weight and scrub radius	Steering can feel heavier and stops get longer
Spare Tire Storage	Carrier, tailgate, or underbody room	Stock spare location may no longer work

That list is why a 37-inch setup that feels great on one truck can feel clumsy on another. The tire is only one piece. Suspension design, wheel specs, gearing, and body shape all decide how easy the swap will be.

How To Pick The Right 37 For Your Build

If you’re staring at a pile of size options, narrow the choice with these steps.

Start With Your Current Setup

Check the tire placard, your current wheel size, and the room you already have at full lock. That gives you a clean starting point. A truck that already clears a true 35 on the stock wheel may need a smaller jump than you think. A Jeep with trimmed fenders and the right bump-stop setup can swallow more tire with less drama.

Pick Width Before Tread Pattern

A lot of buyers choose the tread style first. Width is the call that changes fitment sooner. A 37×12.50 is the usual sweet spot for many trail rigs and daily-driven lifted trucks. It keeps the stance full without pushing the tire out as far as a 13.50. If you want a narrower tall tire, LT315/80R17 is often the size people end up circling back to.

Match The Tire To The Wheel You Want To Keep

If you already own 17-inch wheels you like, stay in the 17-inch side of the 37 market. That gives you a taller sidewall, which can ride softer and puts more rubber between the wheel and rocks. If you run a 20-inch wheel, you still can get a 37, though the sidewall is shorter and the tire has a different look on the truck.

Read The Brand Spec Sheet Before Ordering

This step saves money. Two tires with the same labeled size can carry different actual diameters, widths, tread depths, and weights. If your build is close on gearing or clearance, those small differences are not small at all once the tire is mounted.

The Number To Watch Is Actual Height

So, what size are 37 inch tires? In plain English, they’re tall off-road tires that sit near 37 inches in diameter, usually run 12.5 to 13.5 inches in width, and fit wheels from 17 to 20 inches. The exact tire you buy may stand a bit under that mark once you read the real specs.

If you want the cleanest answer for fitment, buy by the full size code and the brand’s spec sheet, not the nickname on the sidewall. That one habit will tell you more than the “37” ever can.