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275/45R21 tires: size explained

275/45R21

275/45R21 is a Euro-metric tire size. It is about 30.7 in (781 mm) tall, 275 mm wide, and made for a 21-inch wheel.

What 275/45R21 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.
275Section width
The tire's width is 275 millimeters (10.8 in), measured from sidewall to sidewall.
45Aspect ratio
The sidewall height is 45% of the width. For 275 mm that is about 4.9 in (124 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.
21Wheel (rim) diameter
The tire is made for a wheel 21 inches across. Its overall diameter is larger: about 30.7 in (781 mm).

275/45R21 dimensions

30.7 inOverall diameter: 30.7 in (781 mm)Rim diameter: 21.0 in (533 mm)Sidewall height: 4.9 in (124 mm)10.8 inSection width: 10.8 in (275 mm)Sidewall height: 4.9 in (124 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
10.8 in (275 mm)
Sidewall height
4.9 in (124 mm)
Wheel (rim) diameter
21.0 in (533 mm)
Overall diameter
30.7 in (781 mm)
Circumference
96.6 in (2453 mm)
Revolutions per mile
656

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

Which vehicles use 275/45R21?

These vehicles list 275/45R21 among their verified sizes, by trim. Open one to see all of its sizes.

Shop for 275/45R21 tires

Confirm the size on your tire sidewall or door placard first. These links open each store's own search for 275/45R21; prices and stock are on their sites.

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Snow chains and tire socks for 275/45R21

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 275/45R21. Whether they suit your vehicle depends on its clearance and the local rules.

Snow chains for 275/45R21 (Amazon search, opens in a new tab)Tire socks for 275/45R21 (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 275/45R21. 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 275/45R21
SizeWheel diameterDiameter differenceCalculator
265/70R1616 in (different)-0.45%Compare 275/45R21 with 265/70R16
265/65R1717 in (different)-0.59%Compare 275/45R21 with 265/65R17
245/75R1616 in (different)-0.90%Compare 275/45R21 with 245/75R16
LT245/75R1616 in (different)-0.90%Compare 275/45R21 with LT245/75R16
265/70R1717 in (different)+2.80%Compare 275/45R21 with 265/70R17
LT265/70R1717 in (different)+2.80%Compare 275/45R21 with LT265/70R17

Same dimensions, different load standard

P275/45R21 (P-metric) has the same dimensions as 275/45R21, but it is built to a different load standard. Check the load index on the sidewall rather than assuming the two are interchangeable.

Compare 275/45R21 with similar sizes

Side-by-side dimensions and speedometer difference for sizes close to 275/45R21 in overall diameter.

Compare 275/45R21 with another size

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

Compare 275/45R21 with another size

Questions about 275/45R21

What does 275/45R21 mean?

275/45R21 describes the shape and size of a tire, not how much it can carry or how fast it can go. 275 is the width in millimeters, 45 is the sidewall height as a percentage of that width (about 124 mm), R is the construction type and 21 is the wheel diameter in inches.

How tall is a 275/45R21 tire?

A 275/45R21 tire has a nominal overall diameter of about 30.7 in (781 mm), with a sidewall about 4.9 in (124 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 275/45R21 tire make?

About 656 revolutions per mile, based on a circumference of 96.6 in (2453 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 275/45R21 the same as P275/45R21?

They have the same dimensions: both are about 30.7 in (781 mm) tall and 275 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 275/45R21?

Among the common sizes we list, these are within about 3% of the overall diameter of 275/45R21: 265/70R16 (-0.45%), 265/65R17 (-0.59%), 245/75R16 (-0.90%), 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.