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 No. 726 Berkshire Locomotive W/ 2426w Tender From 1948-49 (dakotapaul)Marx Army Military Set 5926g In Original Box Excellent-500,851m,572st,572,558mSet Of Two Lionel 0/07 Gauge #2354 New York Central F-3 Diesel LocomotivesRare Postwar Lionel 2338 Solid Stripe Milwaukee Road Gp7 Diesel, C-7 Ex, No Rsv!Postwar Lionel Type Zw, 275 Watt 60 Cycles Trainmaster Transformer With BoxLionel 00, 5342 New York Central Hudson, 4-6-4, 1939-1942, Lionel Oo W Box, Oo2Vintage Prewar Lionel O Gauge Hiawatha Streamlined Passenger Set 782 & 783 & 784Scarce Lionel Postwar 6517 Erie C301 Bay-window Caboose Mint W/box (dakotapaul)Vintage Prewar Lionel O Gauge No.250e Hiawatha Steam Engine & TenderIves "the White Owl" No. 502 Passenger Train Set, Complete W Original Box, 1927Lionel O Gauge #736 2-8-4 Steam Engine In Beautiful Condition Lionel Post War O Electronic Control 671 Steam Engine 526234Ives Conductors Outfit Set From 1927, Complete In Original Box!!!Lionel Post War 773 Hudson Locomotive & 773w Tender In Original Box's C-8 LnO Scale Vintage Brass Trolley. Rare ! American Flyer? Lionel?Lionel Postwar Set Madison Heavyweights 2625 2627 2628 Passenger Cars DakotapaulMth Premier 20-3061-1 4-8-4 Gs-2 Southern Pacific Sp Steam Locomotive Dcs Ps 2.0Postwar Lionel 2378 Milwaukee Road Ab, F3 Diesels, C-7 Ex, Run Great, No RsvPostwar Lionel 3672 Bosco Operating Milk Car~scarce Painted Version~nice Orig!Marx Pre-war Mercury New York Central Passenger TrainLionel 6-38029 Union Pacific 4-12-2 Steam Locomotive & Tender W/tmcc&rs Ex/boxUs Hobbies Brass 0-8-0 Switcher Locomotive Only 2-rail O Custom Painted U.s.Lionel Postwar Ab Mkt Diesel Set "texas Special" #2245 With #2245c TenderOriginal Lionel 2329 Virginian Rectifier In Ob - No ReserveLionel Post War 726 2-8-4 With Smoke Bulb & 2426w Tender In Original Box's NiceMth #20-2178-1 Union Pacific O Gauge Dd40ax Diesel Locomotive W/proto Sound ObOriginal Lionel 6805 Atomic Energy Disposal Car In Ob - Outstanding - No ReserveWilliams J Class 4-8-4 O Gauge Norfolk & Western #j-100 Steam Locomotive ObPostwar Lionel 622 Santa Fe Nw2 Diesel Switcher W/bell~nice Original!Lionel 00, 5342 New York Central Hudson Tender, 1939-1942, Lionel Oo W Box, Oo2tOutstanding Green Engine Lionel 6520 Searchlight Car +box No Reserve (dakotapaulLionel Original 2640 2640 2641 Green Prewar Passenger CarsMarx / Gray Mercury / New York Central / Five Piece Train / ArticulatedMth Premier O 20-3128-1 2-8-4 Nyc P&le A2 Berkshire Steam Locomotive Dcs Ps 2.0Nice! Lionel No. 404 Postwar Baltimore & Ohio Budd Mail Car + Box (dakotapaul)Mth Atsf/santa Fe Sd24 Premier Diesel Engine With Ps2 #20-2410-1Lionel K-line 4-6-2 Railsounds Tender Pacific Steam Locomotive Prr Mth WillaimsPostwar Lionel 736 Berkshire Steam Locomotive & 736w Whistle Tender~w/nice Ob'sPostwar Lionel 2344 New York Central,f3, Aa Diesels, C-7 Ex, Runs Fine, No Rsv Lionel 0/027 Gauge Alaska Railroad Diesel Locomotive Freight Train Set RunsOn3 Brass Pfm T-12, 4-6-0...never Run, Display Model Only.Pre-war American Flyer Train Set Engine, Tender & 3 Cars, Station, Lamp & TracksHornby Series O Gauge Clockwork No 1 Lms 0-4-0 Tank Locomotive - 1925 VersionOriginal Lionel 6407 Flat Car With Sterling Missile - No ReservePostwar Lionel No. 11590 Complete Boxed 212 Santa Fe Passenger Train Set, C-7 E Postwar Lionel Set No. 1407b From 1946, 1665 Switcher & 3 Freight Cars, C-7 ExclO Scale (2 Rail) Atlas, Dash 8-40bw Diesel Locomotive, Santa Fe Mint New In BoxVintage Lionel 6-8363 B&o F-3 A Unit Powered Diesel Engine In Box Ob �� Marx Boxed Two Level Train Set, # 25340, Freight & Passenger, Complete2004 Lionel 24183 Esso Gas Station NosOn2 Brass Sr&rl #23 Locomotive, By The Car Works, Still New And Unused, Mint.Ives O Gauge Train Set #572 Blue Vagabond C.1930-montgomery Ward Spec. W/ob OsbLionel 6-18598 New York Central Nyc Rs-11 Command Odyssey Tmcc RailsoundsVintage Prewar Lionel No.436 Power StationNice Lionel No. 2031 Rock Island Aa Alco Diesel Set W/ Box No Res (dakotapaul)Postwar Lionel 2343 Sante Fe Pair Aa & 4 Aluminum Passenger Cars Train 0 ScaleMth Railking Trains 30-2699-1 Jersey Central Gp9 Diesel Locomotive O ScaleLionel Train Us Army Lrrc Tofc Flat Car W/truck & Tanker Trailer Set 6-52336 Scarce Lionel No. 2544w Super Chief Passenger Set 2383 2563 + Set Box DakotapaulLionel New York Central Commodore Vanderbilt Streamlined Steamer & Tender Set

Recent News: O Scale Model Trains

Source: Google News

All welcomed aboard at Abington Lines Model Railroad Club
Bucks County Courier Times, February 12th

Wayne Dalton, secretary for the Abington Lines Model Railroad Club, holds a couple of his favorite model engines at the club's headquarters in Northampton on Wednesday, Feb. 10, 2016. The club will hold a free open house from 12 to 4 p.m. Saturday and ...Read more

Unveiled> Two Museums in North Adams
The Architect's Newspaper, February 3rd

Nearby, The Extreme Model Railroad Museum will be a 700-foot-long addition to two historic freight train depots, with a total area of 32,400 square feet. In the museum, O scale model trains (1:48) will move through architectural dioramas created by the...Read more

Somerset 4-H Trainmasters to hold annual Winter Train Show
MyCentralJersey.com, January 26th

Proceeds from the annual winter train show support the Somerset County 4-H Trainmasters' College Fund and other club activities. Each year, the Somerset County 4-H Trainmasters Club awards a $1,000 scholarship to a graduating Senior who is a member ...Read more

The J611 steams again at the Ratcliffe Transportation Museum
Roanoke Times, January 20th

The most famous locomotive of that class, engine 611, and her sister engine 603, are now featured on the Brockmeyer O-scale layout at the Raymond F. Ratcliffe Memorial Transportation Museum. The 1/48 scale models represent a family of 14 Class J ...Read more

What's happening in Annapolis, Baltimore, DC, Eastern Shore and in Ocean City
CapitalGazette.com, January 14th

Baltimore Society of Model Engineers, 225 W. Saratoga St. 410-837-2763 or modelengineers.com. Operating Model Train Display: Two model railroad empires occupying 2,500 sq. ft., operating trains and trolleys in HO & O scale. Free. Now through Jan. 31...Read more

Hampstead business showcases free train garden
Carroll County Times, December 7th

O-scale model trains are 1:48 scale, meaning one scale-inch on the model train represents the equivalent of 48 inches on the real, life-size train. Linda Standiford, one of Roof Right's managers, said many of the company's employees are fairly young...Read more

Model Railroad tour takes train enthusiasts for a ride
St. George Daily Spectrum, November 11th

Just one of 12 model railroad systems that will be open to the public this weekend during the Color Country Model Railroad tour, Schneider's G-scale, or Garden-scale outdoor trains, chug along through a miniature world he has created in the backyard of...Read more

Hop aboard the Halloween train
The San Diego Union-Tribune, October 30th

Eight years ago she bought him an O-scale train set with a Halloween theme because she wanted a fun, not-too-scary, way to entertain young trick-or-treaters. The train was such a hit, they decided to build on their success each year. The layout is...Read more