Channel Tunnel Dimensions: Length, Diameter, and Depth

The Channel Tunnel (Chunnel) is a 50.5 km (31.4 mi) undersea rail tunnel linking Folkestone, UK to Coquelles, France.

Key Dimensions:

• Total Length: 50.5 km (31.4 mi)
• Undersea Section: 37.9 km (23.5 mi) — world's longest undersea tunnel.
• Tunnel Configuration: Three parallel bores:
  • Two running tunnels (rail): 7.6 m (25 ft) internal diameter each.
  • One service tunnel (maintenance/emergency): 4.8 m (16 ft) diameter.
• Cross-passages: Every 375 m connecting all three tunnels.
• Depth Below Seabed: Average 40–50 m (max 75 m).
• Depth Below Sea Level: Up to 115 m (377 ft) at deepest.

The "height" of the running tunnels is 7.6 m (internal diameter), accommodating high-speed trains (Eurostar, LeShuttle) with overhead catenary.