About ModelRailCalc

ModelRailCalc exists because most model railroad questions have an answer that depends on your own layout, and most published answers do not ask about it. What radius you need depends on your longest car and your scale. What grade you can build depends on the run you have. What wire gauge the bus needs depends on its length and your booster. There are 14 calculators here and 198 generated reference pages, and every one of them is built around that idea.

Where the numbers come from

We separate two kinds of figure everywhere on this site, because conflating them is the fastest way to mislead somebody who has been in this hobby for decades.

Sourced and exact. Scale proportions and track gauges follow NMRA Standard S-1.2. Car weights follow NMRA Recommended Practice RP-20.1, which gives each scale a base weight plus an amount per inch of car body length. Copper resistance per thousand feet by wire gauge comes from standard wire tables. Grade, frog angle, ladder geometry, areas and volumes are plain arithmetic that anyone can check, and every calculator shows its working.

Rule of thumb, and labelled as such. Minimum radius as a multiple of car length is hobby convention, not a standard. It predicts real behaviour well, which is why it is used, and NMRA Recommended Practice RP-11 is the standards-body document on curvature. A manufacturer's stated minimum radius for a specific model always takes priority over any general rule, and our pages say so. Typical locomotive current draw figures are planning numbers with editable defaults, and every page built on them tells you to measure your own locomotives.

Where we cannot source a figure, we leave it out rather than estimating it. That is why some spec sheets here are shorter than others.

What we will never claim

We do not test products in person and we never say we do. There is no workshop here with forty locomotives on a test track. Recommendations are researched from manufacturer specification sheets, instruction manuals, published standards and the recurring themes in verified owner reviews. Any site claiming hands-on testing of an entire product category is telling you a story, and we would rather be useful than impressive.

We also do not invent ratings, fabricate owner quotes, or present a specification we cannot attribute. Product prices, images and links come directly from the Amazon Creators API rather than being typed by hand, which is why a price here matches the listing and why a product with no live price shows as "See price" instead of a guess.

How products get recommended

Every roundup is organised in three tiers rather than one flat list, because that is how people actually shop: the lowest total cost to something that works, the buy-once pick, and the performance ceiling. The expert tier always says who should not buy it, and several pages here actively talk you out of a purchase. Sound on every locomotive is noise rather than an improvement. A turntable on a plan with nowhere to put it is money wasted. An oversized booster can damage a decoder in a fault rather than protecting it.

Picks are matched to a real number wherever a number exists: the radius your equipment needs, the current your roster draws, the grade your run allows. A recommendation that contradicts the arithmetic on the same page is a recommendation we have got wrong.

Who this is for

Somebody with a space measured and a decision to make. The calculators are most useful before the track is down, when changing your mind is still free. The reference pages are for the specific question you have at the workbench, and the build lists are for when you want the whole thing costed rather than assembled one purchase at a time.

How this site is paid for

As an Amazon Associate we earn from qualifying purchases made through links here, at no additional cost to you. It never changes which product we recommend, and the pages that tell you to buy less are the evidence. Read the full affiliate disclosure.

Corrections

If a figure here is wrong, we want to know, and that includes the ones we have labelled as rules of thumb. Model railroading has a long institutional memory and a large number of people who have measured these things themselves. Get in touch and tell us what is wrong and what the right figure is.

Researched, not professional advice. Check any radius, clearance or grade against your own equipment before cutting wood or laying rail, because manufacturers vary and so does what your specific models will tolerate. Any permanent mains wiring in a layout room is work for a licensed electrician to your local code.