Z

1:220

-

Very small size, not good for small children

N

1:160

-

Second most common in U.S.

Nn3

1:160

-

Narrow gauge - 3’, also Nn2 and Nn2 1/2 - not common

TT

1:120

1/10"

Table Top - not common in U.S.

HO

1:87.1

-

“H Zero” is technically correct, but pronounced “H - Oh”. Most common scale in U.S. Derived from Half “O” scale

HOn3

1:87.1

-

Narrow Gauge - 3’, also HOn2 and HOn2 1/2, not as common

OO

1:76

-

S

1:64

3/16"

Sn3

1:64

3/16"

Narrow Gauge - 3’, also Sn2 and Sn2 1/2 - not common

O

1:48

1/4"

Pronounced “Oh”, but technically “Zero” 1.25” gauge

On3

1:48

1/4"

Narrow gauge - 3’, also On30(On2 1/2) and On2

Gauge 1

1:32

3/8"

Original 1.75” gauge is now obsolete, currently 45mm or 1.77" based on American Standard Gauge (56.5") and is refered to as "G Scale". Used as the standard for G scale track (45mm).

Gauge 2

-

-

Obsolete

G

1:29

-

Another size in the G Scale spectrum

Half

1:24

1/2"

Another size in the G Scale spectrum

G

1:22.5

-

G Scale based on the European Narrow Gauge (1m) designed to run on Gauge 1 (45mm) track

F (G)

1:20.3

-

Fine Scale or "F Scale" is another in the G Scale spectrum based on American Narrow Gauge (36”) on Gauge 1 (45mm) track

-

1:19

-

Another size in the G Scale spectrum, commonly used for live steam locomotives

-

1:16

3/4"

-

1:8

1 1/2"

Gauge 3

-

2.5"

2.5” gauge (obsolete)

Standard Gauge

-

-

2 1/8” gauge, Lionel, American Flyer and others