How Tall Is a 245/45/20 Tire? | Exact Size Numbers

A 245/45R20 tire measures about 28.68 inches in overall diameter, with a 4.34-inch sidewall height.

For the full breakdown, see our best 245/45ZR20 Tires guide.

If you’re checking clearance under the fender or comparing sizes before buying a set of 245/45R20 tires, the number that matters is the overall height. Calculated from the size markings, that figure comes to roughly 28.7 inches, and it’s the one that decides whether the tire fits your car without rubbing. The 245/45R20 size is a common fitment on modern sedans and crossovers, and knowing its exact dimensions makes the difference between a smooth swap and a costly mistake.

The size label breaks down like this: 245 is the section width in millimeters, 45 is the aspect ratio (sidewall height as a percentage of width), and 20 is the wheel diameter in inches. The R simply means radial construction. That math produces a tire that’s designed for 7.5 to 9-inch wide wheels.

How Tire Size Numbers Turn Into Height

The overall diameter comes from adding the wheel diameter to twice the sidewall height. For this size, the sidewall is 110.25 mm (4.34 inches), and doubling that adds 8.68 inches to the 20-inch wheel, landing at 28.68 inches total.

Those numbers also tell you about the tire’s footprint. The section width is 245 mm, the circumference works out to roughly 90.1 inches, and the tire spins about 704 times per mile. That last figure matters for speedometer accuracy—a smaller or larger diameter changes the reading.

The Mistake That Confuses Everyone

People often mix up sidewall height with overall tire height. The 4.34-inch sidewall is just the rubber between the rim and the tread; it is not the same as the 28.68-inch overall diameter, which includes the wheel. If you’re measuring clearance under the fender, you need the overall number, not the sidewall.

One caveat applies to all these figures: they’re calculated nominal dimensions. A mounted tire can measure slightly different depending on the brand, the specific model, and inflation pressure. Pirelli’s catalog and tiresize.com’s 245/45R20 spec page list the same calculated numbers, but the actual mounted height can vary by a fraction of an inch in practice.

Before you commit to a set, check the clearance at full steering lock and under suspension compression. A quarter-inch of variance can make the difference between a clean fit and a rubbing sound every time you hit a bump.

Fitment and Real-World Application

The 245/45R20 size fits wheels in the 7.5 to 9-inch width range, with 8 inches being the most common match. It’s a popular choice for vehicles that need a balance of ride comfort and handling without going to an ultra-low-profile sidewall.

Because the tire’s diameter directly affects speedometer readings and gearing, staying close to the factory-recommended size matters. Pirelli’s 245/45R20 tire catalog lists the full specification range for this size, which is a solid reference if you’re comparing options. If you’re ready to shop, our tested roundup of the best 245 45zr20 tires covers the top performers and what each does well.

Quick Spec Reference

The table below compresses the key numbers so you can compare at a glance.

That’s the complete size story for a 245/45R20 tire. The short version: roughly 28.7 inches tall overall, about 9.6 inches wide, and designed to bolt onto a 20-inch wheel. Keep those numbers handy when you’re measuring clearance or checking fitment, and you’ll avoid the most common sizing mistakes.