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255/45R20 tires: size explained

255/45R20

255/45R20 is a Euro-metric tire size. It is about 29.0 in (738 mm) tall, 255 mm wide, and made for a 20-inch wheel.

What 255/45R20 means

A tire size describes the tire's shape and the wheel it fits. It says nothing about load capacity or speed capability, which are printed separately on the sidewall.

No letterEuro-metric
With no letter in front of the width, this is a Euro-metric size (also called hard metric). It has the same dimensions as the P-metric version but is built to a different load standard, so its load capacity can differ.
255Section width
The tire's width is 255 millimeters (10.0 in), measured from sidewall to sidewall.
45Aspect ratio
The sidewall height is 45% of the width. For 255 mm that is about 4.5 in (115 mm). A smaller number means a shorter sidewall.
RRadial construction
R means radial construction, where the internal cords run across the tire from one edge to the other.
20Wheel (rim) diameter
The tire is made for a wheel 20 inches across. Its overall diameter is larger: about 29.0 in (738 mm).

255/45R20 dimensions

29.0 inOverall diameter: 29.0 in (738 mm)Rim diameter: 20.0 in (508 mm)Sidewall height: 4.5 in (115 mm)10.0 inSection width: 10.0 in (255 mm)Sidewall height: 4.5 in (115 mm)
Each drawing is to scale on its own. The curves of the tread shoulder and bead are simplified; the table below has the same numbers.
Section width
10.0 in (255 mm)
Sidewall height
4.5 in (115 mm)
Wheel (rim) diameter
20.0 in (508 mm)
Overall diameter
29.0 in (738 mm)
Circumference
91.2 in (2317 mm)
Revolutions per mile
695

These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.

Which vehicles use 255/45R20?

These vehicles list 255/45R20 among their verified sizes, by trim. Open one to see all of its sizes.

Shop for 255/45R20 tires

Confirm the size on your tire sidewall or door placard first. These links open each store's own search for 255/45R20; prices and stock are on their sites.

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Snow chains and tire socks for 255/45R20

Where winter roads call for extra traction, chains and tire socks are two options that fit over your tires. They are made for specific tire sizes, so these links open Amazon searches for 255/45R20. Whether they suit your vehicle depends on its clearance and the local rules.

Snow chains for 255/45R20 (Amazon search, opens in a new tab)Tire socks for 255/45R20 (Amazon search, opens in a new tab)

Paid links to Amazon search results. As an Amazon Associate I earn from qualifying purchases. Read our affiliate disclosure.

Before you buy

  • Chains and socks are sold by tire size, so match the size on your sidewall exactly.
  • Check your owner's manual first: many newer cars and SUVs limit or prohibit chains, or require low-profile (often called SAE Class S) chains because of tight wheel-well clearance.
  • Tire socks are a lighter-duty option; check your state's rules, because some areas only accept chains when chain controls are in effect.
  • Put them on the drive wheels (or as your manual says) and follow the maker's speed limit.

Similar sizes

These common sizes have an overall diameter within about 3% of 255/45R20. A common rule of thumb is to keep a replacement size within about 3% of the original overall diameter. Confirm any size change with your vehicle's owner's manual or a tire professional.

Common sizes with an overall diameter close to 255/45R20
SizeWheel diameterDiameter differenceCalculator
235/65R1717 in (different)-0.03%Compare 255/45R20 with 235/65R17
255/55R1818 in (different)+0.03%Compare 255/45R20 with 255/55R18
235/60R1818 in (different)+0.23%Compare 255/45R20 with 235/60R18
225/65R1717 in (different)-1.79%Compare 255/45R20 with 225/65R17
245/60R1818 in (different)+1.86%Compare 255/45R20 with 245/60R18
235/55R1818 in (different)-2.96%Compare 255/45R20 with 235/55R18

Same dimensions, different load standard

P255/45R20 (P-metric) has the same dimensions as 255/45R20, but it is built to a different load standard. Check the load index on the sidewall rather than assuming the two are interchangeable.

Compare 255/45R20 with similar sizes

Side-by-side dimensions and speedometer difference for sizes close to 255/45R20 in overall diameter.

Compare 255/45R20 with another size

See how another size differs in height, width, sidewall and speedometer reading in the tire size calculator.

Compare 255/45R20 with another size

Questions about 255/45R20

What does 255/45R20 mean?

255/45R20 describes the shape and size of a tire, not how much it can carry or how fast it can go. 255 is the width in millimeters, 45 is the sidewall height as a percentage of that width (about 115 mm), R is the construction type and 20 is the wheel diameter in inches.

How tall is a 255/45R20 tire?

A 255/45R20 tire has a nominal overall diameter of about 29.0 in (738 mm), with a sidewall about 4.5 in (115 mm) tall. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.

How many revolutions per mile does a 255/45R20 tire make?

About 695 revolutions per mile, based on a circumference of 91.2 in (2317 mm). A vehicle's speedometer and odometer are calibrated to the tire size it was built with, so a size with a different overall diameter changes what they read. A common rule of thumb is to keep a replacement size within about 3% of the original overall diameter. Confirm any size change with your vehicle's owner's manual or a tire professional.

Is 255/45R20 the same as P255/45R20?

They have the same dimensions: both are about 29.0 in (738 mm) tall and 255 mm wide. They are built to different load standards, though (Euro-metric and P-metric), so the load a tire can carry can differ. Check the load index on the sidewall, and ask a tire professional or your owner's manual before treating them as interchangeable.

Which sizes have a similar diameter to 255/45R20?

Among the common sizes we list, these are within about 3% of the overall diameter of 255/45R20: 235/65R17 (-0.03%), 255/55R18 (+0.03%), 235/60R18 (+0.23%), and 3 more. Diameter is only one measure. Width, wheel diameter, load capacity and clearance matter too. Confirm any size change with your vehicle's owner's manual or a tire professional.

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Paid links to Amazon search results. As an Amazon Associate I earn from qualifying purchases. Read our affiliate disclosure.