• Converting real life dimensions to HO

  • Discussion related to everything about model railroading, from layout design and planning, to reviews of related model tools and equipment. Discussion includes O, S, HO, N and Z, as well as narrow gauge topics. Also includes discussion of traditional "toy train" and "collector" topics such as Lionel, American Flyer, Marx, and others. Also includes discussion of outdoor garden railways and live steamers.
Discussion related to everything about model railroading, from layout design and planning, to reviews of related model tools and equipment. Discussion includes O, S, HO, N and Z, as well as narrow gauge topics. Also includes discussion of traditional "toy train" and "collector" topics such as Lionel, American Flyer, Marx, and others. Also includes discussion of outdoor garden railways and live steamers.

Moderators: 3rdrail, Otto Vondrak, stilson4283

  by scrag104
 
Hello fellow railroaders,

I know that this is a stupid question but what is the equation to convert real world dimensions to HO? E.G. 40' real world equals how many inches in HO. I am drawing a real blank on the formula right now. Any help would be greatly appreciated.

Scott
  by Tom Curtin
 
The usual conversion factor is 87.1

  by Throttle_JCKY
 
One actual foot (12") equals 87 scale feet.

  by pdt
 
X x 12
______ = Y

87.1

where "X" is real world feet

and "Y" is inches

So, your example 40 x 12 = 480 inches
480 / 87.1 = 5.5109 inches

Clear as mud now? :-D

  by Sir Ray
 
Not too exciting, but 1 inch (real) ~ 7.25 feet (HO)

This may help you estimate scale if you're in a discount store and see some potentionally useful toy vehicles or buildings which look like they are close to HO.

  by NYC-BKO
 
It is easier to use metric 3.5 mm equals one foot in HO.

Easier yet is to get a scale rule, which has HO scale feet, plus inches, I have a one foot one and a 6" one ( pocket size ) for taking with me to stores. Very useful tool.
There is a website where you can print one, but it eludes me right now, I can't remember which forum I saw it on.

Found the link to printable scale rule!
http://www.fiddlersgreen.net/images/n-horule.pdf

  by scrag104
 
Why and when did the scale change from 1/87 to 1/87.1? Thanks for giving me the conversion formula, I was drawing a real blank.

Thanks,
Scott

  by scopelliti
 
The ratio of 3.5 mm to the foot gives an exact ratio of

1 : 87.085714285714285714285714285714

Most folks round this to 1:87.1 or 1:87 which both have an error of less than .1 %

Modeling a one foot item at 1:87.1 vs exact scale would give a difference of two hundreth thousandths of an inch.
  by Tom Curtin
 
Wow --- love all those decimal places! You know, there may be some modelers out there who count those two hundred thousandths of an inch . . .
  by retired grouch
 
A reply to "scrag 104" and others

Many years ago, a member of the club to which I belonged at that time gave me the following formulae:

HO: Scale feet to actual inches where scale feet = X.
(1. (X) x .1379 = actual inches in thousands of inches

(2. take decimal number and multiply by .64 to get 64th of inch.

e.g. 20 scale feet
(1) 20 x .1379 = 2.758 (inches)
(2) .758 x .64 = 48512
(3) final solution =2-48/64" or round off to 2-3/4"


Since this is now also an N gauge forum also

(1. (X) x .075

e.g. 20 scale feet
-(1. 20 x .075 =1.5 (inches)


Try it. Pick a set of plans from your favorite model railroading mag. Get out the calculator, run the numbers, then double check with a ruler. But still go out and buy a scale ruler. Much easier.

Hope this helps.

Retired grouch in "Joisey"