NMRA Scale Weight Calculator

December 4^th, 2018

I recently started working on a few projects to build and upgrade some rolling stock cars for my HO scale train collection.  In doing so, I searched the internet to find the best practices and standard weights for rolling stock.  I discovered an article by Roger Hensley on the NMRA website and began using the information and weight guides in that article as my standard guide for weighting my rolling stock.

Originally, I would round-off to the nearest half an ounce based on the nearest quarter-inch measurement of my train car.  Once familiar with the formula, it is easy to remember and calculate them.  However, I’m one of those people who will check the math twice and double or triple check my measures and even having memorized the formula, I would occasionally refer back to the NMRA’s article to reassure myself that I was making the correct calculation.

I’ve seen in a few Model Railroader magazine articles where they reviewed new rolling stock from manufacturers and assess points for different features, weight being one of them.  I was surprised to see once that a particular Scale Trains model having superb detail across the board was far off in the weight class.  One day I’ll want an NMRA representative to review and evaluate one or more of the projects I’m working on and wish to be certain that I build or upgrade models and stay within an acceptable weight range for the size model I’m having evaluated.  At that time, I’m likely to be a little more precise and therefore decided that I should make a Rolling Stock Car Scale Weight Calculator.  I could have easily put such a calculator in a spreadsheet but then I thought to myself, access to the calculator would be limited to times and places where the spreadsheet was available to me.  It would be far more convenient for me to create the calculator on one of my websites and therefore be able to access it from any device anywhere I could get Internet Access.  This would also prove a useful tool for many other interested parties and might also go towards another NMRA AP Awards that I may apply for in the future.

All that being said, feel free to use Henry’s NMRA Rolling Stock Car Scale Weight Calculator to calculate the standard weight of any rolling stock that you might have or may be working on.  Note that I have provided the ability to provide the weights in Metric as well as English.

Henry’s NMRA Rolling Stock Car Scale Weight Calculator

Here is an excerpt from the Roger Hensley NMRA article (edited and re-ordered alphabetically by me):  The below table is reproduced from NMRA RP-20.1. To find the optimum weight of a given car, select your scale and find the “Initial Weight”.  Then take the “Additional Weight” and multiply this by the number of actual inches in the length of the particular car.  Add this weight to the “Initial Weight” for the total Optimum Weight of the car.  In HO, a 6 inch car should weigh 4 ounces.  That is a 1 ounce minimum plus 1/2 ounce per inch of car: 1 + 3 = 4 ounces.

I hope you find this calculator useful in your model railroading endeavors.

Henry
Completed and Published: 12-5-2018.