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    

Rare Original 1942 Betty Grable Fan Club Photo With Her 1136 Lionel Train Set LnNice! Lionel Prewar # 763e Steam Hudson Loco W/ 263w Tender No Res (dakotapaul)Lionel Train Set #2046 Engine,tender,5 Cars,transformer & Original BoxesLionel Collector Quality 1950 773 Hudson & 2426w Tender With Boxes, Runs Great Lionel Pre War 2-6-2 Locomotive 224e & Diecast Tender 2224w Passenger Set 14w1946 Lionel 726 Berkshire Steam Loco & 2426w Tender With Boxes, C-7 Ex, No Rsv Bing For Bassett Lowke Clockwork Tin Plate Lms 513 Precursor Locomotive O GaugeVintage 1930 Prewar Dorfan No.426 Railroad Passenger Station HouseRare 1957 Set: Lionel 2373 Canadian Pacific F-3 Aa Units & 2551, (2) 2552 2554Lms 789 Live Steam Locomotive O Gauge No Apparent Makers Mark No ReserveStreamliner Rare Hiawatha Orange W/set Box Lionel Prewar Toy Train 5213 Jr Runs0/027 Lionel,postwar, Sante Fe #2343 Aa F3 Diesel Set, Exc Cond, 1950/53 MustseeRare Postwar Lionel 6464-325 Baltimore & Ohio Sentinel Boxcar, C-7 Ex & No Rsv!Lionel Pre-war "o" Gauge 238e & 3ea 600 Pass. Cars-1937-orig. Set Box-very Nice!Nice Original Prewar Lionel 436 Power Station - Standard Or O GaugePostwar Lionel 2333 New York Central F3 Aa Diesels~w/nice Ob's & InstructionsMth, 4-6-2 Forty-niner Steam Engine, Union Pacific, 30-1139-1, Rare!Very Nice Original Prewar Lionel 435 Power Station - Late Colors? - Super Clean!Vtg Lionel Train 773 & Coal Tender 2426w Locomotive Black EngineLionel Pre-war 616w Streamline "flying Yankee" Set 616w (2) 617 & 618 & BoxesAmerican Flyer Prewar O 572 Steam Engine 4-8-4 Nice Drive Train 531304Postwar Lionel 2343 Santa Fe F3, Aa Diesels, Look Fine, Run Great, No Reserve!Prewar Lionel Jr 1700 Streamlined Passenger Train Set, Very Nice, Runs GreatAmerican Flyer Prewar O 4-8-4 572 Steam Engine Big Engine 531305Postwar Lionel 2023 Union Pacific Alco Aa Diesels In Ob, C-7 Ex, Run Fine No RMth 20-3028-1 New Jersey Central 4-6-2 Blue Comet Steam Locomotive Exc. Cond.!Lionel Prewar Blue Comet 2613 2614 2615 Passenger Cars - No ReserveLionel Post-war "o" Gauge 2344c Nyc F-3 B Unit-unrun-1953-orig. Box-gorgeous!Lionel Pre-war 2623 Set/3 "manhattan" Deluxe Passenger Cars-1941 Originals-nice!Post War Lionel 2333p And 2333t Emd F3 A-b Santa Fe Diesel LocomotivesLocomotive Workshop 150 Or 250 Ton Wreck Crane Kit (2-rail)Rare Lionel Prewar # 260e Gun Metal Gray Engine W/263t Tender Ob (dakotapaul)Mth 20-3042-1 Chesapeake & Ohio M-1 Steam Turbine With Proto 2 Read Discription Vintage Prewar Ives O Gauge Limited Vestibule Passenger Car Set 129 & 129 & 130Original Lionel 2339 Wabash Emd Gp7 Diesel Locomotive In Ob - No ReservePostwar Lionel 0 027 Diesel Engine Locomotive Santa Fe 2343 Good Shape W/ Box American Flyer Prewar O 534 Reletter 4-8-4 Union Pacific Northern Steam Loco Marx Diesel Train Set Western Pacific 901 Passenger Cars 1007 1217 #44464 #bl3Prewar Lionel Blue Streak Streamliner Passenger 617 618 619 O Gauge Lionel Post-war "o" Gauge #2334 Nyc F-3 A-a Diesels-1949-orig. Boxes-very Nice!Lionel 226e Prewar Steam Locomotive - No Reserve Lionel Pre War 2-4-0 Steam Locomotive (ives)1661e With Tender (1933) American Flyer Prewar O 572 4-8-4 Up Northern Steam Loco 336 Number Boards 5Postwar Lionel 245x Steam Locomotive (uncataloged) & 1130t Tender~w/scarce Ob'sPostwar Lionel Set. No. 1800 “the General Frontier Pack", 1862 Gen. & Cars, ExclPostwar Lionel 6823 Flatcar With Irbm Missiles~mint Unrun~w/nice ObLionel 2226w Prewar Large Whistle Tender For 763e 226e Steam LocomotiveLionel Postwar Two Original " Lionel " Automobiles W. Rare Cardboard Wrap0/027 Lionel Polar Express Train Set,nice Diecast Smoking Steamer,vgc Must SeeLionel Trains Postwar No.2400 Series Green Passenger Car Set W/boxes, O GaugeAmerican Flyer 3380 3187 3382 3381 Car Prewar O-gauge Lot Train Loco For PartsLionel 6-38176 Pennsylvania Alco Fa A-a Diesel Locomotive Set0/027 Lionel, # 6-8054 Burlington F3 A Diesel Set, With 5 Aluminum Pass Cars,excAll Original Mint Lionel 6820 Aerial Missle Transport Car W/rare Original Box NrO Gauge Mth Sd70ace Nyc Diesel Engine #1954, 20-20086-1 Lionel 2481s "anniversary Set 2482,2483 (1950) O27 GaugeVintage Exley Tinplate Lms O Gauge No Carriage Coach No ReserveTin Old Girard Marx The Joy Line Railroad Train Set O Scale Wind Up Toy Cars American Flyer Prewar O Restored 567c Union Pacific Tender Sound Unit 531241Lionel 746 Norfolk & Western Northern Short Stripe, Ex-ex+ Tender Ob, No Res!

Recent News: O Scale Model Trains

Source: Google News

Fiddlers Grove Train Museum starts Model Train Club
Lebanon Democrat, April 27th

This will be an all-scale model railroad club. Currently, the Fiddlers Grove Train Museum has an extensive “O” gauge layout and a small “H O” scale layout with plans to expand the “HO” track. The club will be open to anyone interested in model train...Read more

Clubs briefs Journal April 27
Casper Journal, April 26th

The members of the Central Wyoming Model Railroad Association have been saddened by the departure to his Eternal Rest of one of our charter members, Bob Baden. He was Wyoming's first NMRA master model railroader, and for many years, the only one in the...Read more

Model train tours to make stops in Ligonier, Latrobe, Greensburg
Tribune-Review, April 25th

It includes hand-held remote devices that synchronize train movement with the sounds of chugging engines and screeching brakes and puffs of simulated smoke and diesel exhaust. Most of Sheats' train sets are at “O” scale, in which 1 inch equals 4 feet...Read more

Town Crier: Clubs
Casper Star-Tribune Online, April 23rd

We are planning on working on the 100+ year-old baggage cart and getting it refurbished with new wood. And we will be working on Bob's 'O' Scale layout to make it more user friendly and bring it into use more frequently. We welcome any assistance that...Read more

Clubs briefs
Casper Journal, April 14th

The members of the Central Wyoming Model Railroad Association have been saddened by the departure to his Eternal Rest of one of our charter members, Bob Baden. He was Wyoming's first NMRA master model railroader, and for many years the only one in the...Read more

Model railroaders hope new St. Paul site gets hobby back on track
Minnesota Public Radio News, April 11th

The exhibit had to be cut into movable pieces. The O-Scale Exhibit, which is the centerpiece at Twin City Model Railroad Museum, is a display depicting the influence of the railroad on Minneapolis and St. Paul from the 1870s through the 1950s. Tom...Read more

Railroad watching at Business After Hours
Oskaloosa Herald, April 10th

OSKALOOSA – Penn Central Model Railroad Inc. is proud to host the next Business After Hours Thursday, April 14 from 4:30-6:30 p.m. at their showroom in Penn Central Mall. Come see train layouts featuring N, HO and O scale trains carrying several ...Read more

Saluda Grade train model donated to Saluda Historic Depot
Tryon Daily Bulletin, March 31st

Just like building a railroad up a steep grade, Dr. McConnel was challenged building a train model of the Saluda Grade because of the space limitations in the depot building. Instead of drawing the O scale model to scale in width, he would go up and...Read more