Calculators
Tools for HO modellers
Three quick calculators. They work in any browser — with or without JavaScript — and the scale ratios come from the published standards, linked on each page.
- Scale calculatorTurn a real-world size into HO (1:87) — or measure a model and find the full-size equivalent. N, TT, OO, S and O are shown alongside, and you can enter any ratio.
- Curve radius & layout spaceHow big a board an oval needs at a given radius, how much track goes round it, the full-size curve it represents, and the steepness of a gradient.
- Rail codes comparedWhat “code 100” and “code 83” mean: rail height in millimetres and inches, and the full-size rail each one represents.