O scale refers to a model railroad train that is 1/48th the size of a real train—in the U.K., O scale trains are generally 1/43rd the size of the real thing while in Europe they are 1/45th as big. Like a real train, O scale model railroad trains run on two-rail tracks. The gauge of those tracks is O, which describes tracks whose rails are 1 ¼ inches apart. Even though O scale model trains frequently run on O gauge tracks, strictly speaking, the two Os have nothing to do with each other.

The letter "O" is actually a misnomer since the designation was initially conceived to identify trains that were smaller in scale than 1, which had been the standard. Since the only number smaller than 1 is 0, that’s how early O scale trains and O gauge tracks were identified. Similarly, HO was originally intended to describe a scale and gauge that is half (H) of zero, but the letter O (pronounced “owe”) crept into everyday use among model train buffs and has remained the way to refer to zero ever since.

Confused? A lot of people are. But for those who are first and foremost focused on O scale, nothing else matters. For these enthusiasts, replicating the detail of a full-scale train in an equally detailed layout is the only goal.

An O scale model train’s tracks, as it turns out, are a key part of creating a sense of realism. When an O scale train is run on three-rail O gauge tracks (the middle rail delivers the power to the locomotive) such as those made by Lionel, the train rides higher off the surface than it would in real life, thus shattering the illusion. Model railroaders who run O scale trains on three-rail tracks are known as hi-railers. It’s not quite a put down, but it isn't really a compliment, either.

Toy manufacturers in the early part of the 20th century originally embraced the O scale so they could offer customers model trains that took up less space than their standard-sized counterparts. Because they were smaller, these trains were also less expensive. At one time or another, Märklin, Lionel, MTH, Williams, Atlas, and Weaver, among others, all offered O scale trains. Fans of brass model trains are also frequently O scale acolytes because the earliest, most collectible brass trains made in postwar Japan were usually O scale.

The smaller scale took off in the 1930s, when affordability trumped most other concerns thanks to the Depression. The scale also benefited from its adoption by industry leader Lionel, which sold two O gauges for its O scale trains. Lionel’s regular O gauge track was the same width as its O-27 gauge track (1 ¼ inch), but the O-27 had a lower profile than regular O, and its thinner rails allowed all but the longest O scale model trains to make tighter turns (a circle of O-27 tracks has a diameter of 27 inches instead of 31).

Today, neither appeal to O scale purists who put accuracy and authenticity above mere convenience. There is even a vocal contingent of two-rail O scale enthusiasts who advocate for the conversion of model trains designed to run on three-rail tracks to model trains that will run on just two. This often requires changing a train’s trucks (the framework for the axles and wheels) as well as a layout’s wiring (from AC to DC), but the lower profile that results makes an O scale model train look a lot less like a toy and more like the real thing.

Best of the Web (“Hall of Fame”)

Airfix Model Railways

Airfix Model Railways

Dave McCarthy's Airfix Model Railway treasure trove is an in-depth archive of the company's plastic railway kits fr… [read review or visit site]

Gateway NMRA

Gateway NMRA

This great reference site for model railroaders, from the Gateway (St. Louis) division of the NMRA (National Model … [read review or visit site]



This site is a treasure trove of HO scale model railroad manufacturer catalogs and other reference information, inv… [read review or visit site]

Postwar Lionel Trains Library

Postwar Lionel Trains Library

Bernie Schulz’s Lionel Trains Library focuses exclusively on postwar Lionel trains and accessories. The site cont… [read review or visit site]

Eric's Trains

Eric's Trains

Eric Siegel's site displays his collection of O-gauge/O-scale trains, tracks, turntables, and other accessories. A … [read review or visit site]

Tech Model Railroad Club of MIT

Tech Model Railroad Club of MIT

MIT's model railroad club, as one might expect, has one of the best websites for learning about how people play wit… [read review or visit site]

Clubs & Associations

Discussion Forums

Other Great Reference Sites

Most watched eBay auctions    

Lionel Gun-metal Gray 763e Hudson Rare 2226wx Tender Freight Set 787w DakotapaulLionel 675 Engine & 2466wx Tender W/ Obs, Early Version, Runs, OriginalK-line O Scale Train Heavyweight U.s. Army Troop Kitchen Pass Car K4899-0004 NewLionel Pre-war 700e Loco Only, For Parts, Bad Boiler, The Rest Is GoodLionel 2426w Lionel Lines Die Cast Whistle Tender~nice Original!K-line O Scale Train Heavyweight U.s. Army Hospital Car K4899-0005 New Mth Z4000 TransformerLot 586 - Lionel O Gauge - Santa Fe F3 Diesel A-a Unit Set No. 2343 Lionel 763e Nyc J1-e Hudson Steam Engine #5344, Item# 18056 W. Tmcc, Rs & BoxO Scale Brass Lobaugh 2-8-4 Berkshire With Tender Two Rail1950 Lionel 773 Hudson With 2426w Whistle Tender SetMth Premier Union Pacific Sd40-2/ 20-2669-1Original Lionel O Gauge #254 4 Wheel Pre-war Tinplate Electric Train EngineLionel 0/027 Gauge #8576 Penn Central Gp-7 Diesel Engine In The Original Box1947 Lionel Lines 2426w Whistle Tender ***shell*** With Full TrimLionel 2343 Santa Fe F-3 Aa Diesel...tested...2 Motors...ob W/ Master Carton BoxOverland Models Up 2906 4-6-2 Streamlined Brass Engine & Tender 2 Rail O ScaleOriginal Lionel 1504 Uncataloged Freight Set - No ReserveOriginal Lionel 6828 Mobile Contruction Crane Car In Ob - No ReserveLionel 2340 Pennsylvania Gg-1 Electric LocomotiveO-on3-on30-on2 - Stoney Creek Designs - Hodges Drug & Chemicals - Structure KitAmerican Flyer Die Cast O Gauge Yard King Switcher Locomotive 0-6-0 With TenderK Line Nyc J1e Hudson With Tmcc & Railsounds K3270-5343s New Good Mth & LionelLionel 1950 Madison 2627 Manhattan 2628 Irvington 2625 Passenger CarsO Scale On3 On30 The Market Crossroads Collection Stoney Creek Ccl 03 O.p.Lionel Anniversary Passenger Cars 2481 2482 2483 1950Ives 257 And 257 TenderO Scale Sunset Models Brass - 2 Rail Southern Pacific Rr Ge 44 Ton Switcher Prewar American Flyer 572 Steam Engine.Marx 027 Gauge #36256 Steam Engine Type Electric Train Passenger SetLionel 665 Locomotive O Gauge Engine & 2046w Tender 1954 As Is2 Rail O Scale Brass Misc. Union Pacific Mofw Rolling StockK-line O Scale Train Bnsf Gp38-2 Dual Motors Horn And Dynamic BrakesCustom Brass Little River 2-4-4-2 O-on3-on30-on2 - Stoney Creek Designs - Blacksmith Shop - Structure KitLionel Set Of 3 Madison Cars, 2625, 2627, 2628, Clean, OriginalDorfan Outfit No. 256 "siver-blue Arrow"...1930-1933 Only. Steal It!!!Lionel Trains Santa Fe Fa # 204 Diesel Engines Post War O Scale 1957 1 BoxLionel Trainmaster Transformer Type Zw 275 Watt Train Controller With BoxLionel 2420 Work Caboose W/ Searchlight & Ob, Clean, Unbroken, OriginalAmerican Flyer Die Cast Engine And TenderSunset Brass Southern Pacific Ac-12 Cab Foward Steam Engine. O Scale 2 Rail. SpLionel 2640 Series Two Tone Green 3 Car Passenger Set, Very Clean, OriginalOriginal Lionel 2559 B&o Rdc Budd Car In Ob - No ReserveLionel 4671 Electronic Engine Only, 1946 Version, Runs, OriginalBrass O Scale 2 Rail Transfer Caboose One Of A Kind 501041Super Quality O Gauge Electric Crewe Type 2-2-2 Steam Locomotive And TenderO Scale Brass Prr N5 Decorated Caboose 5010431977 Lionel Trains-walt Disney Mickey Mouse Express-o-27-complete Boxed Set(14)Lionel 2360 Pennsylvania Gg-1 Pwd. Electric LocomotiveLionel 218 Santa Fe Alco Units & 600 Mkt Nw-2 Switcher As IsLionel Canadian National No. 8031 Gp-7 With Postwar Lionel Frame And Drive TrainLionel 356 Baggage Carts And 2 Scarce LoadsM.t.h. # 30- 1164 Prr L-1 Mikado Steam Engine W/proto 2 SoundsVintage Lionel Nyc 221 Locomotive & No. 221t Tender Post War O Scale Runs FineLionel Postwar No. 2240 Wabash F-3 A&b Diesel LocomotivesLot 585 - Williams O Gauge - Pennsylvania S-2 Turbine 6-8-6 Engine & Tender SetLot 571 - Lionel Postwar O Gauge - No. 671 Locomotive & 671w TenderVintage Lionel 671w Whistle TenderO Scale Brass Hines 4-6-2 K5 Steam Locomotive Outside Third Rail Erie

Recent News: O Scale Model Trains

Source: Google News

RI train expo offers something for everyone
Quad-Cities Online, March 1st

"As soon as he said, 'Choo-choo,' we started buying Thomas," Mr. Genung said of the popular children's train toys Sunday during the Great Train Expo at the QCCA Expo Center. "We've graduated from Thomas to O scale, and now we're into HO. We're ...Read more

ALL ABOARD! End of the line for state's biggest HO scale layout in downtown ...
The Daily Jeffersonian, February 13th

The Guernsey Valley Model Railroad club began 40 years ago. This weekend, after traveling thousands of miles, the H-O scale trains will reach the end of their line. The club modeled the layout after Southeastern Ohio, featuring Guernsey County as a...Read more

18th annual Rails in the Rockies this weekend
Estes Park Trail-Gazette, February 11th

Other displays include: American Flyer Interactive Layout; Colorado Wyoming LEGO@ User Group (CoWLUG) layout (this year with a surprise theme) a circus train exhibit; and, Slim Rails Layout from Colorado Springs. There will be multiple layouts in...Read more

Depot museum open this Saturday
State Gazette, February 4th

Carlton Willis places a grass mat on the new Lionel, O-scale, train board inside the Newbern Depot Museum. The new train board was constructed by City of Newbern employees and is approximately 16 feet long and 5 feet wide. The new train board stands at ...Read more

The Trains of Christmas Display Hits 25th Anniversary
WHAG, November 29th

HAGERSTOWN, Md - The Hagerstown Roundhouse Museum (HRM) celebrated its 25th anniversary Saturday with sounds and smells of Christmas past and present with an "O" scale toy train track as part of the Trains of Christmas display. The toy train ...Read more

Model trains by the mile on view at this exhibit
NJ.com, November 18th

Members of the 80-year-old society operate a train museum and two large "railroad empires" that include model train layouts that cover almost 4,000 square feet. The larger "O" Scale layout is 40 by 70 feet and has almost 20 scale miles of train track...Read more

Massive model train club in Paterson invites Halloween visitors (PHOTOS)
The Star-Ledger, October 24th

The NJ HiRailers claim to have the largest "O-scale" layout in the country, at 185 feet by 40 feet. O-gauge refers to the scale of the layout, which is 1:48. Hunterdon County's Northlandz, which claims to be the largest model layout in the world, is HO...Read more

Fairbanks man builds elaborate model train layout
Kenai Peninsula Online, April 27th

In a friend's warehouse space, he's building a layout for large “O-scaletrains. It's probably the largest O-scale layout in the Interior, he said. O-scale is one of the largest scales for model trains. With a 1:48 scale, each inch in the model world...Read more