Metric tire size

235/45R18 tire size

A 235/45R18 tire is 26.3 inches (669 mm) tall and 9.3 in wide, for a 18-inch wheel, with a 4.2 in sidewall. That is the nominal size worked out from the code. Makers publish 26.1–26.6 in for real 235/45R18 tires (7 makers).

Diameter26.3 in669 mm

Width9.3 in235 mm

Sidewall4.2 in106 mm

Revs per mile766nominal, published 785–795

Wheel width7.5–9 inapproved by every listing

Compare 235/45R18 with other sizes

Set up for: comparing 235/45R18 with a size you're considering · Different situation?

Your current size

Current tire size

e.g. 265/70R17, 2657017 or 33x12.50R20

Where do I find my size?

It's on the tire sidewall, e.g. P265/70R17 115T, and on the tire placard sticker on the driver's door jamb (also in the owner's manual). The placard shows the size the vehicle came with; the sidewall shows what is fitted now. If they differ, use the placard as your starting point. Digits are enough here: 2657017 or 33125020.

Size you're considering

Size you're considering (2)

Real 235/45R18 tires: published diameters

Figures from the makers' own data books. They differ from the 26.3 in calculated figure because each tread design and construction measures slightly differently.

Maker (data book)	Published diameter	Revs per mile	Approved wheel width	Listings
BFGoodrich	26.3 in	790	7.5–9 in	1
Falken	26.3–26.6 in	785–791	7.5–9 in	5
Goodyear	26.3 in	793	7.5–9 in	1
Hankook	26.1–26.5 in	788–795	7.5–9 in	9
Nitto	26.38 in	—	7.5–9 in	1
Toyo	26.3 in	789	7.5–9 in	1
Uniroyal	26.3 in	790	7.5–9 in	1

Sources: maker data books (PDF), checked 2026-11-05. Brand names identify the data source only.

Equivalent sizes on other wheels

Sizes that appear in the maker data books with a diameter within 3% of 235/45R18. Same diameter is only one part of fitting a different size.

Wheel	Real sizes within 3% (closest first)
15-inch	205/70R15 (26.3 in, −0.1%), 235/60R15 (26.1 in, −0.9%), 245/60R15 (26.6 in, +0.9%)
16-inch	205/65R16 (26.5 in, +0.6%), 215/60R16 (26.2 in, −0.6%), 255/50R16 (26.0 in, −1.1%)
17-inch	215/55R17 (26.3 in, −0.1%), 235/50R17 (26.3 in, −0.3%), 255/45R17 (26.0 in, −1.1%)
18-inch	265/40R18 (26.3 in, +0.1%), 305/35R18 (26.4 in, +0.3%), 215/50R18 (26.5 in, +0.5%)
20-inch	265/30R20 (26.3 in, −0.3%), 225/35R20 (26.2 in, −0.5%), 235/35R20 (26.5 in, +0.6%)

Popular comparisons with 235/45R18

225/50R18 vs 235/45R18−2.0% diameter

FAQ

How tall is a 235/45R18 tire?

26.3 inches (669 mm) calculated from the size code. Makers publish 26.1–26.6 in for real tires in this size; the difference comes from tread design and construction.

How do you work out the 235/45R18 diameter?

Sidewall = 235 mm × 45% = 105.8 mm. Diameter = 18 in wheel + 2 × 105.8 mm ÷ 25.4 = 26.33 in.

Is 235/45R18 a 26-inch tire?

It is about 26.3 in tall nominally, so it is close to 26 inches. Real tires in a size vary slightly by model; check the maker's spec sheet for the exact tire.

What sizes are equivalent to 235/45R18?

Real sizes within 3% of its diameter include 205/65R16 (+0.6%), 215/55R17 (−0.1%) and 265/30R20 (−0.3%). Equal diameter alone doesn't make a size suitable: wheel width, offset, clearance and load rating all matter.

How many revolutions per mile does a 235/45R18 make?

About 766 calculated from its unloaded diameter. Makers publish 785–795 revs per mile, measured under load (a loaded tire rolls on a slightly smaller radius), which is why published figures are higher.

Open 235/45R18 in the converter · Tire size chart

Important: These are calculated (nominal) dimensions, not a fitment recommendation. Real tires of the same size differ by brand and model (makers allow about ±3% of section height), and width changes with the rim it is mounted on. The math can't see wheel width and offset, clearance at full steering lock and suspension travel, load index, speed rating, or what your vehicle maker approves. Before changing size, check your door-jamb placard and owner's manual and ask a tire professional. A replacement tire must meet or exceed the load index and speed rating on the placard.