Point Spacing Calculator — Turnout Layout

Leave at least one vehicle length of straight track between consecutive points so a long coach or bogie wagon is never spanning two sets of moving switch blades at once. For OO gauge with standard 260-280mm coaches, allow at least 280mm of straight between the frog (V-crossing) of one point and the toe (switch end) of the next. Shorter sidings and yard pointwork can be tighter because speeds are low.

For mainline running use medium (Peco SL-95, 219mm, 12° frog) or large radius (SL-88, 259mm, 12°) points so long coaches and bogie stock track smoothly. Small radius (SL-91, 185mm, 12°) points are best kept for sidings and yards where speed is low. Peco Streamline offers small, medium and large radius turnouts in OO; N gauge code 80 has a medium (SL-395, 123.7mm, 12°) and large (SL-388, 160mm, 8°) plus the tighter Setrack ST-5 (87mm, 22.5°).

Peco Streamline standard OO double-track spacing is 50mm centre-to-centre — generous radii allow down to about 44mm (the 4mm-scale prototype minimum) before adjacent coaches foul on curves. Hornby Setrack uses a wider 67mm fixed geometry. N gauge runs at roughly 25-26mm centres. Tighten spacing only on straight track and check clearances with your longest stock on the sharpest curve before committing.

A crossover connects two parallel tracks using two points facing opposite directions. The along-track footprint it occupies equals the track-centre spacing divided by tan(frog angle): at the Peco 12° frog, a 50mm-centre OO crossover needs about 235mm of bench length. Use matching point sizes for both sides, and keep the straight section between the two frogs long enough for your longest vehicle.