Flotation tire size

37x12.50R20 in metric

A 37x12.50R20 is a flotation size: 37.0 inches tall and 12.5 in wide, for a 20-inch wheel (940 × 318 mm). Makers publish 36.5–37 in for real 37x12.50R20 tires (5 makers).

Diameter37.0 in940 mm

Width12.5 in318 mm

Sidewall8.5 in216 mm

Revs per mile545nominal, published 565–572

Wheel width8.5–11 inapproved by every listing

Compare 37x12.50R20 with other sizes

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). If your current tires aren't the original size, the placard shows what the vehicle came with. Digits are enough here: 2657017 or 33125020.

Size you're considering

Real 37x12.50R20 tires: published diameters

Figures from the makers' own data books. They differ from the 37.0 in calculated figure because each tread design and construction measures slightly differently.

Maker (data book)	Published diameter	Revs per mile	Approved wheel width	Listings
Falken	36.8–37 in	569–572	8.5–11 in	2
Goodyear	36.8 in	565–566	8.5–11 in	2
Hankook	36.6–36.7 in	569–572	8.5–11 in	2
Nitto	36.54–36.77 in	—	8.5–11 in	2
Toyo	36.5–36.8 in	565–569	8.5–11 in	2

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 37x12.50R20. Same diameter is only one part of fitting a different size.

Wheel	Real sizes within 3% (closest first)
15-inch	37x14.50R15 (37.0 in, ±0.0%), 38x15.50R15 (38.0 in, +2.7%)
16-inch	385/70R16 (37.2 in, +0.6%)
17-inch	37x11.50R17 (37.0 in, ±0.0%), 37x12.50R17 (37.0 in, ±0.0%), 37x13.50R17 (37.0 in, ±0.0%)
18-inch	37x11.50R18 (37.0 in, ±0.0%), 37x12.50R18 (37.0 in, ±0.0%), 37x13.50R18 (37.0 in, ±0.0%)
20-inch	37x11.50R20 (37.0 in, ±0.0%), 37x13.50R20 (37.0 in, ±0.0%), 38x13.50R20 (38.0 in, +2.7%)
22-inch	37x12.50R22 (37.0 in, ±0.0%), 37x13.50R22 (37.0 in, ±0.0%), 38x13.50R22 (38.0 in, +2.7%)

FAQ

How tall is a 37x12.50R20 tire?

37.0 inches (940 mm) calculated from the size code. Makers publish 36.5–37 in for real tires in this size; the difference comes from tread design and construction.

Is 37x12.50R20 a 37-inch tire?

It is about 37.0 in tall nominally, so it is close to 37 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 37x12.50R20?

Real sizes within 3% of its diameter include 385/70R16 (+0.6%), 37x11.50R17 (±0.0%) and 37x11.50R18 (±0.0%). 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 37x12.50R20 make?

About 545 calculated from its unloaded diameter. Makers publish 565–572 revs per mile, measured under load (a loaded tire rolls on a slightly smaller radius), which is why published figures are higher.

Open 37x12.50R20 in the converter · Tire size chart · 37-inch tires

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.