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

TT Scale
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TT scale model railroad
Scale110 inch to 1 foot
Scale ratio1:120
Standard(s)NEM, NMRA
Model gauge12 mm (0.472 in)
Prototype gaugeStandard gauge

Its 1:120 scale (from a common engineering scale where one inch equals ten feet) and 12 mm (0.472 in) gauge are roughly halfway between HO scale (1:87) and N scale (1:160). Its original purpose, like the name suggests, was to make a train set small enough to assemble and operate on a tabletop.

The scale originated in the USA, but is today widespread mainly in Central Europe, thanks to "Berliner Bahnen", a defunct East German manufacturer of train sets in TT. It is the second-most popular scale in Central Europe and Russia, after HO, and adherents to TT maintain it is the smallest practical scale, especially for those who like to build models from scratch. In other parts of the world it is less spread, and can be described as a niche scale in the United States and the United Kingdom.

In wargaming, the TT scale 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.

In Europe, Rokal and Zeuke (which became Berliner-TT-Bahnen and ultimately Tillig) also began production in West and East Germany respectively. British Tri-ang Railways introduced the scale to the UK, although due to the smaller British loading gauge, the trains were scaled up to 1:101.6 (or 3 mm scale) to have room for motors and other electric equipment. For a while it enjoyed considerable success, but it was not meant to last.

By the early 1960s, TT had been eclipsed in popularity by N scale, which is smaller. Tri-ang quit the scale in 1967, and H. P. Products discontinued manufacturing their TT line in 1968, and the related tooling and kits have been passed through several hands. In West Germany, Rokal ended production in 1969.

In East Germany, then on the other side of the Iron Curtain, production continued. Berliner-TT-Bahnen, which had superseded Zeuke, widened its offerings and exported trains and tracks over most of the Eastern Bloc. As the range became more and more comprehensive, offering not only trains and tracks but also accessories such as signals, lights and working catenaries, it became a serious contender to HO. During the 1980s, trainsets were also exported to the West, offered as simple and cheap entry-models to the hobby and earning East Germany much-needed hard currency.

With the end of the Cold War, the East German economy was liberalised. Berliner-TT-Bahnen started to update their offerings, but soon ran into financial hardship. The company eventually ended up in the hands of Tillig, still today the largest provider of TT equipment. The products were improved, with better technology and more details, to bring them up to date with the offer in other scales.

Trains from Kuehn and Piko in TT scale.

In the 1990s and 2000s, several other companies started to offer models in TT, including major brands such as Piko and Roco, but these decades also saw the emergence of brands such as Kuehn, Beckmann and Kres, which all have made their mark in the scale. Since then, interest in the scale has grown, and more models are now available than in Z scale, and TT has come close to rivalling N (at least for European models), not the least with the 2022 entry of British Hornby and their new TT:120 range.

British TT 3 mm scaleEdit

British TT, TT3 or 3 mm scale
Scale ratio1:101.6
Model gauge12 mm (0.472 in) 13.5 mm (0.531 in) 14.2 mm (0.559 in)[1]
Prototype gaugeStandard gauge

As mentioned above, traditional British TT, or TT3,[2] is 3 mm scale; that is, 1:101.6. The reason for the slightly larger scale was that the available motors in the 1950s were too large to fit in the British loading gauge. The simple solution was, just like in choosing OO over HO and as later would happen in N gauge, to make the trains slightly larger but keeping the track at international scale.

The "Three Millimetre Society"[1] is a British-based society which caters for railway modellers of 3 mm scale. This society was formed in 1965,[3] eight years after Tri-ang Railways, a British railway manufacturer, had introduced their TT locomotives and rolling stock. The aims of the society are to encourage modellers working in this scale, and it produces a quarterly magazine and assists with the production of locomotive and rolling stock kits, components and the supply of secondhand items and spares.

British TT:120Edit

Commercial support for British outline TT:120 was introduced in June 2022. It has a scale of 2.54mm to the foot or one tenth of an inch to the foot and uses 12mm gauge track, just like the TT scale used both in the USA and continental Europe. The new scale was announced in June 2022 by the UK manufacturer PECO. The company launched its new TT:120 scale 12mm gauge code 55 track and UK prototype accessories.[4][5] Writing in the Peco Publications & Publicity magazine, Railway Modeller, editor Craig Tiley stated, To explain: rather than perpetuating the hybrid combination of 3mm:1ft scale and 12mm gauge track that was adopted by Tri-ang for its TT range during the 1950s and '60s, Peco has instead chosen the accurate scale and gauge combination of 2.54mm:1ft on 12mm track. This equates to a ratio of 1:120 (hence the term TT:120) which represents a brand new scale for commercial items in British outline.[6]

On the same date as PECO's unveiling of their range, UK-based manufacturer Gaugemaster announced plans to introduce a new range of products for TT:120 scale, which could have included Class 66 locomotives, subject to demand.[7] In their October 2022 (free subscription) newsletter Gaugemaster stated, "Following Hornby’s news that they have developed an expansive range of TT:120 products which they intend to supply exclusively via their own website, it makes little or no commercial sense for us to develop a complimentary range of products in this scale."

A few days after PECO's venture into TT:120, Danish model railway manufacturer Heljan announced plans to produce a British Rail Class 31 locomotive with possible future developments of a British Rail Class 08 locomotive and a Hunslet Austerity 0-6-0ST locomotive, all in TT:120 scale.[8] Following the October 2022 announcement of Hornby's new TT:120 range, which included all three of Heljan's planned releases, Heljan announced that it was ceasing development of its TT:120 models, followed shortly after by Gaugemaster.[9]

In October 2022, British brand Hornby released its new range of TT:120.[10] Two train sets are being offered, with four series of locomotives and rolling stock available. This is only available from Hornbys own website it is not available from retailers.


Currently Tillig is the largest company to make TT scale rolling stock. Most TT scale track sold today is also made by Tillig, which offers both standard model railroad track and an integrated roadbed track using Kato's Unijoiner system. But the growing interest for the scale has led to more manufacturers during the last few years, and the scale has also attracted some of the big actors within other scales. Roco launched their first TT products in 1998, and has a small but growing line. Smaller producers like Kuehn and Beckmann have widened their product lines in recent years, just like Dutch PSK Modelbouw and Czech MTB, which specializes in Czech, Slovak and Polish models.

Russian Peresvet is another manufacturer who produces TT scale models, mostly Russian prototypes. German large scale manufacturer PIKO has also started with a TT line, focusing mainly on German stock, and offer locomotives, wagons and several EMUs. Arnold launched their first new TT models since being bought by Hornby in 2014, and has a small but growing offer. In 2022 Hornby also announced a new TT programme with British trains, offering a wide range of locomotives, carriages and accessories, reintroducing the scale in Britain. This time, however, the models are in continental TT scale, not the slightly larger scale of the old Tri-ang products.

There is a larger variety in the accessories market, where some companies have a long-time involvement with the scale and others recently started to support it as well. Prototypes are mainly German and Central European, with a wide offer of models from Czech, Slovak, Polish, Swiss and Austrian environments. Suppliers of accessories are for example Auhagen, Noch and Viessmann. British Triang produced a Continental/French range but it was only made for a very short while.

The scale is uncommon outside Central Europe, but there are a few manufacturers in other parts of the world. One current producer of British TT is 3 mm Scale Model Railways[11] who supply updated GEM and BEC TT kits as well as a large range of Brass Etch and Resin body kits. American manufacturers include Possum Valley Models (kits), Sleepy Hollow/Gold Coast (ready to run and kits, Costal Engineering (kits) DnS TT Track and others.[12]

List of some TT manufacturers (not complete):

  • Auhagen - landscape material
  • Beckmann - trains
  • Fischer-Modell - trains
  • Gützold - trains
  • Herpa - landscape material
  • Hornby - Locomotives, rolling stock, track, accessories, digital system
  • IGRA - wagons and buildings
  • Kres - trains
  • Kuehn - trains, track, accessories, digital system
  • MTB - trains
  • Noch - landscape material
  • Peresvet - trains
  • Piko - trains, digital system
  • PMT - trains
  • Polák - landscape material
  • PSK Modellbouw - trains
  • SDV Model - wagon kits
  • Sommerfeldt - catenaries
  • Tillig - trains, track, accessories, digital system
  • Viessmann - accessories, catenaries

Track systemsEdit

There are several track systems available in the scale. Tillig offers two different tracks: with trackbed and without. The latter system is considerably more developed, while the former has a more limited choice but comes with two different kinds of track bed. Most TT modellers use one of these two, partially because of the widespread availability. The smallest recommended turn radius is 310 mm, but track with tighter curves, 267 mm, is available. Most rolling stock, however, is designed to work on the 310 mm curves, and might not work on smaller radia.

German manufacturer Kuehn also offers a track system, which is slowly growing, adding more turnouts and other parts as time goes by. The geometry differs slightly from Tillig's system, but the two are compatible although with some minor differences.

With Hornby's entry into the scale in 2022, a completely new track system was launched. While having its own distinct appearance, the geometry is in most aspects the same as Tillig's track.

Several other track systems are available, although with smaller choice of track pieces. The old, u-shaped track of Berliner TT Bahnen is also still available, but usually not advertised. Czech manufacturer DK-Model also offers a limited range of TTe narrow gauge track, consisting of points and flexible track. Moreover, the British manufacturer PECO introduced Streamline Flexible Track and Medium Radius Turn-Outs with code 55 rail in June 2022.[4]


Standards useful to both manufacturers and modellers are maintained by MOROP in Europe. These standards are generally the same for such elements as track gauge, scale ratio, couplings, and electrical power, and differ for clearances and other factors that are specific to the prototype being modelled.

TT scale locomotives are powered by DC motors which accept a maximum of 12 V DC. In traditional DC control, the speed of the train is determined by the amount of voltage supplied to the rails. The direction of the train is determined by the polarity of the power to the rails. Digital train control systems have, just as in other scale, become more and more common. The most popular digital control systems used in TT scale model railways is NMRA-DCC, most commonly using systems from Roco, Uhlenbrock, Kuehn, Piko or Tillig.

There are several coupling systems used in TT. Rokal and Zeuke had simple hook-and-ring systems for their model, but these are hardly in use anymore. Berliner TT Bahnen introduced a modernized coupling in the 70s, and this is still today the standard coupling on models from some manufacturers. The most common coupling today, however, is the Tillig close coupling system, and most ready-to-run models are equipped with this. There are also different systems for magnetic couplings, permanent couplings and so on, and some modellers also use Kadee-style couplings.

Practically all TT scale rolling stock made today is equipped with coupling pockets according to the standard NEM358. This means all modern models have interchangeable couplings.

Related scalesEdit

Variations include TTn3 (NMRA) or TTm (NEM), where TT scale is run on N gauge (9 mm / 0.354 in) track for narrow gauge operation. In New Zealand this is known as NZ120,[13] and is growing in popularity as a means of modelling the nation's 3 ft 6 in (1,067 mm) gauge railway network. TT9 is modelling using British TT scale on 9 mm track to model 3 ft (914 mm) gauge lines.

TTe uses 1:120 scale on Z gauge (6.5 mm / 0.256 in) track to represent narrow gauges around 750 millimetres (2.5 ft).

Several scales also use TT gauge but with a larger scale to represent narrow gauge railways. The most common are HOn3½ gauge (which represents 1067mm gauge in 1/87 HO scale) and H0m gauge (representing metre gauge track also for 1/87 HO scale).

See alsoEdit


  1. ^ a b "The 3mm Society". Retrieved 2020-09-18.
  2. ^ Flint, Steve (July 2020). "TT:120 - does the hobby really need this new ready-to-run scale for British outline?". Railway Modeller. Vol. 73, no. 861. p. 461.
  3. ^ "Over 50 Years of 3mm Modelling". The 3mm Society. 1997. Retrieved 2020-09-18.
  4. ^ a b "Resurgence of model railway hobby sees PECO's launch of the much-loved but long-forgotten TT:120 British outline scale". PECO. 6 June 2022. Archived from the original on 6 June 2022. Retrieved 6 June 2022.
  5. ^ Morgan, Jack (6 June 2022). "Peco TT (1:120 Scale) Range Announcement - Hattons Model Railways". Archived from the original on 6 June 2022. Retrieved 8 June 2022.
  6. ^ Tiley, Craig (July 2022). "TT:120 - Peco goes full circle". Railway Modeller. Vol. 73, no. 861. p. 451.
  7. ^ "NEW Gaugemaster TT Scale Range". 7 June 2022. Archived from the original on 7 June 2022. Retrieved 7 June 2022.
  8. ^ Jones, Ben (14 June 2022). "No Compromises – British outline 1:120 TT is here!". Heljanuk. Archived from the original on 14 June 2022. Retrieved 14 June 2022.
  9. ^ Jones, Ben (13 October 2022). "HELJAN TT:120 - Update". Archived from the original on 13 October 2022. Retrieved 14 October 2022.
  10. ^ "Hornby reveals huge range of models for TT:120". PECO. Archived from the original on 10 October 2022. Retrieved 10 October 2022.
  11. ^ 3mm Scale Model Railways.
  12. ^ "All aboard for TT Scale on-line". TT Scale on-line. Archived from the original on 25 June 2017. Retrieved 15 June 2022.
  13. ^ "NZ120 - home of NZ120 model standard". Retrieved 23 July 2022.

External linksEdit