What is the minimum curve radius for OO gauge?

The absolute minimum for OO gauge is about 371mm (1st radius Hornby/Peco), but this looks very sharp. 438mm (2nd radius) is better for most locos. 610mm or larger is recommended for coaches, and 762mm+ for long coaches like HST sets.

Why do longer vehicles need larger radii?

Longer vehicles overhang on curves — the body swings out while the bogies follow the track. On tight curves, this can cause derailments, uncoupling, and unrealistic appearance. Larger radii keep the vehicle body aligned with the track.

What radius do Peco set track curves use?

Peco Setrack for OO uses 371mm (1st radius) and 438mm (2nd radius). Streamline track can be bent to any radius. Hornby uses similar radii. For realistic running, use the largest radius your space allows.

Can I use transition curves?

Yes. Real railways use transition curves (easements) where the radius gradually changes from straight to full curve. You can replicate this with flex track by gradually increasing the curve. It looks more realistic and reduces derailment risk.

ModelCalcs

Curve Radius Calculator — Minimum Track Curves

Find the minimum and recommended curve radius for your rolling stock and scale.

Gauge

Longest Rolling Stock

Board Width (mm)

Limits maximum curve radius

How We Calculate This

Uses published minimum radius guidelines for different gauges and rolling stock types, plus your board width constraint.

Typical Minimum Radii (OO Gauge)

Small locos / wagons: 371mm (Peco 1st radius)
Standard locos: 438mm (Peco 2nd radius)
Coaches: 610mm
Long coaches (HST etc.): 762mm+
Recommended = Minimum x 1.3

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify quantities before purchasing materials.