What Size Is a 33 Inch Tire? Metric Sizes for 33s and 35s

"33 inch tires" and "35 inch tires" are how most truck and Jeep owners talk about size, but almost every tire on the shelf is labeled in metric. A 33 might be sold as 285/75R16, 275/60R20 or 33x12.50R20, and only one of those has the number 33 in it. Here are the metric sizes that make a 33 and a 35, worked out to the tenth of an inch, and how to read the flotation sizes that skip metric altogether.

Why a 33 inch tire has a metric size

The "33" is the overall diameter: the height of the tire from the ground to the top of the tread. A metric size does not print that number. It gives you the width in millimeters, the sidewall as a percentage of that width, and the wheel diameter in inches, so the height has to be worked out:

1. Multiply the width by the aspect ratio and divide by 100 to get the sidewall in millimeters.
2. Divide by 25.4 to turn it into inches.
3. Add the sidewall twice, once above the wheel and once below, to the wheel size.

For a 285/75R16 that is 285 times 0.75, or 213.75 mm, which is 8.4 inches. Then 16 plus 8.4 plus 8.4 gives 32.8 inches. That is a 33 inch tire. The full method, with a chart of widths, is in our guide to tire size in inches.

Metric sizes that make a 33 inch tire

Anything from about 32.5 to 33.5 inches is sold and talked about as a 33. These are the common ones, grouped by wheel size. Select a size to see the tires we have in it.

Two things stand out. First, the same height is possible on every common wheel size from 16 to 22 inches, because a bigger wheel simply gets a shorter sidewall. Second, the widths differ by well over an inch. A 265/70R18 and a 305/55R20 are both 33s, but the 305 is about 1.6 inches wider, and that matters more for fender and suspension clearance than the extra tenth of height.

Is a 285 a 33 inch tire?

Sometimes. The 285 is only the width, about 11.2 inches. Whether the tire is a 33 depends on the aspect ratio and the wheel:

• 285/75R16: 32.8 inches. Yes, this is the classic 33.
• 285/70R17: 32.7 inches. Yes.
• 285/65R18: 32.6 inches. Yes, at the short end.
• 285/60R20: 33.5 inches. Yes, at the tall end.
• 285/55R20: 32.3 inches. Closer to a 32.
• 285/60R18: 31.5 inches. No, this is a 31 to 32.
• 285/45R22: 32.1 inches. No, this is a 32.

The same applies to 275s: a 275/70R18 at 33.2 inches and a 275/60R20 at 33.0 inches are 33s, while a 275/65R18 at 32.1 inches is not quite.

Metric sizes that make a 35 inch tire

True 35s are rare in metric. Most of the sizes sold as metric 35s are a little under 35 inches tall, and the flotation sizes in the next section are far more common at this height.

The 315/70R17 is the size most people mean by "a 35 in metric". It is about 0.6 inches shorter than a true 35, which is why some owners who want the full height move to a 35x12.50R17 instead. In between, the 275/65R20 at 34.1 inches is often described as a 34.

Flotation sizes: 33x12.50R20 and 35x12.50R20

Many off-road and light truck tires use flotation sizing, which is already in inches. A 33x12.50R20 reads as:

• 33: overall diameter, about 33 inches.
• 12.50: section width, about 12.5 inches.
• R: radial construction.
• 20: wheel diameter, 20 inches.

Often the size ends in LT, as in 33x12.50R20LT, which marks a light truck tire with a light truck load range. The common flotation sizes at these heights:

• 33 inch: 33x12.50R15, 33x12.50R17, 33x12.50R18, 33x12.50R20, 33x12.50R22
• 35 inch: 35x12.50R17, 35x12.50R18, 35x12.50R20, 35x12.50R22, 35x13.50R20
• 37 inch: 37x12.50R20, 37x13.50R20, 37x13.50R22

The height in a flotation size is a nominal figure. A mounted tire sold as a 33 often measures a little under 33 inches, and the exact number varies by brand and tread pattern, so check the manufacturer's spec sheet when clearance is tight.

What is 33x12.50R20 in metric?

No metric size matches a flotation size exactly, because a 12.50 inch width works out to about 317 mm, which falls between the metric widths. The closest matches by height:

Most of the metric options are narrower than the flotation tire they replace. That is often the point: a narrower tire at the same height can clear where a full 12.50 does not.

Know the size you want? Search it to see the tires available in it:

Before you move up to 33s or 35s

A taller tire changes more than the look of the truck. Four things to check first:

• Clearance. Some full-size pickups clear a 33 with little or no change. Many smaller trucks and SUVs need a leveling kit, and 35s usually need a lift. Wheel offset and width matter as much as the tire. A tire shop or the suspension manufacturer can confirm what fits your vehicle.
• Speedometer. A taller tire covers more ground per turn, so the speedometer reads low. Going from a 265/70R17 at 31.6 inches to a 33.0 inch tire is about 4 percent taller: at an indicated 60 mph you are doing about 62.7. Going from 32.8 to 35.0 inches is about 7 percent, or roughly 64 mph at an indicated 60.
• Load rating. Flotation and LT sizes carry light truck load ranges such as C, D or E. A passenger metric size of the same height can carry a different load index. Check the load rating against your door placard, especially if you tow.
• Weight and gearing. Taller tires are heavier and effectively change your final drive ratio. Expect slower acceleration and lower fuel economy, more so with 35s than 33s.

The verdict

A 33 or a 35 is a height, not a size. To find one in metric, work out the overall diameter from the width, aspect ratio and wheel, or use the charts above. The metric choices on each wheel size let you pick a narrower or wider tire at the same height, and the flotation sizes give you the full 12.50 width. Whichever you choose, confirm it clears your vehicle and carries the load rating on your door placard before you buy. For the rest of the numbers on the sidewall, see our guide to what tire numbers mean.