Model railroad calculators and honest gear takes. For HO, N, and O scale hobbyists building actual layouts (not just oval loops on plywood).
Model railroad content online is mostly two extremes. NMRA technical standards documents (definitive but dense). Or YouTube layout-tour videos that skip the planning math. The space between them is the practical work most hobbyists actually need.
These tools live in that space. Minimum curve radius so your six-axle diesels actually go around. Grade percentage so locomotives don't stall on the inclines. Scale conversions for when you find an O-scale building you want to use on an HO layout.
Tools
Minimum Curve Radius Calculator
By scale, longest car, and operating speed. Tells you the radius needed before you commit to a track plan that won't work.
Grade and Helix Calculator soon
Run length needed for a given rise, by scale. Plus helix radius math so trains don't stall on the climb.
Scale Conversion Calculator soon
HO to N to O. Convert prototype measurements to scale measurements and vice versa.
Plain note about money: Some product links are affiliate (eBay Partner Network). Small commission on purchases. Doesn't change your price. Reviews come from running real layouts. Atlas track is reliable; some brand-new "code 83" track from no-name vendors has gauge problems out of the box.