TT gauge

TT Scale
TT scale model railroad
Scale	1⁄10 inch to 1 foot
Scale ratio	1:120
Standard(s)	NEM, NMRA
Model gauge	12 mm (0.472 in)
Prototype gauge	Standard gauge

TT scale is a niche model railroading scale, whose name stands for table top.

Its 1:120 (1:130 in Russia and ex-USSR, 1:101.6 in UK) scale (from a common engineering scale where one inch equals ten feet) and 12 mm (0.472 in) gauge sizes it almost halfway between HO scale (1:87) and N scale (1:160). Its original purpose, like the name suggests, was to make a train small enough to be able to assemble and operate it on a tabletop.

TT retains a comparatively small niche in the United States and in the United Kingdom, but growing popularity in the former East Germany; it is the second most popular scale in Eastern Europe and Russia. Adherents to TT maintain it is the smallest practical scale, especially for those who like to build models from scratch.

In wargaming the TT scale roughly equals the 15 mm scale where the height of "standard" 180 cm (70.87 in) soldier height is 15 mm (0.59 in).

TT scale was invented in the United States by Hal Joyce, a former automotive designer. He founded a company, H. P. Products, in 1945, and the first advertisement appeared in 1946. The product line included locomotive kits, passenger and freight car kits, track and detail parts.

By the early 1950s it had a following, offering less detail than HO—considered by some to be an advantage at the time—and a lower price than most other scales. Numerous other companies began offering TT scale trains, track, and accessories as well, and TT scale became popular in Europe in addition to the United States. In the immediate period afterward, several other manufacturers also began production of TT items, notably the Kemtron Corporation (founded by Levon Kemalyan, which manufactured metal castings in several scales. Rokal and Zeuke (which became Berliner TT-Bahnen and ultimately Tillig) also began production.

By the early 1960s, TT had been eclipsed in popularity by N scale, which is smaller. H. P. Products discontinued manufacturing their TT line in 1968, and the related tooling and kits have been passed through several hands. Rokal ended production in 1969.