How to read a tire size: what does 205/55 R16 mean?

July 28, 20264 min read

Every tire has a code like 205/55 R16 91V on its sidewall. It gives the tire's size and main specs. Let's go through what each part means.

What 205/55 R16 means

Part	Meaning
205	Tire width in millimeters
55	Aspect ratio: sidewall height as a percentage of the width. Here it's 55% of 205 mm, or about 113 mm
R	Radial construction. Almost all modern passenger tires are radial
16	Rim diameter in inches
91	Load index. 91 means 615 kg per tire
V	Speed rating. V means 240 km/h

We cover the last two in separate articles with charts: load index and speed rating.

How do you work out a tire's overall diameter?

A tire's overall diameter is the rim diameter plus two sidewall heights. For 205/55 R16: the rim is 16 x 25.4 = 406 mm, the sidewall is 113 mm, and the overall diameter is 406 + 2 x 113 = 632 mm. When you switch to a different size, keep the overall diameter close to the original. Otherwise the speedometer reads wrong and the tire may rub against the body.

Where can you find your size?

On the sidewall of your current tires.
On the factory placard by the driver's door.
On the inside of the fuel filler door.
In your car's owner's manual.

A car often has several approved sizes. Use our vehicle search to find the factory-recommended tire sizes for your make and model.

You know your size. What about prices?

Pick your size and see every offer on one page. On the tire search page, just choose the width, aspect ratio and rim diameter. For what the other markings on a tire mean, see our guide to tire sidewall markings.

Jul 28, 2026

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4 min

Tire speed rating: what do the letters mean?

Letters like T, H and V on a tire are its speed rating. Our chart shows the maximum speed for each letter and explains how to choose the right rating.