Gradient (grade)

The gradient states how steeply a track climbs — as a percentage (rise per run, e.g. 3% = 3 cm per 100 cm) or as a ratio (1:33). Model railway rule of thumb: up to 2.5% is unproblematic, from 3% long trains struggle, above 4% is a last resort. Gradients consume surprising amounts of run: gaining 10 cm at 3% takes more than 3.3 m of track.