Train from London St Pancras International to Portsmouth Harbour
🇬🇧 London St Pancras International → 🇬🇧 Portsmouth Harbour
Straight-line Distance
107 km
SW (220.3°)
Rail Distance
~139 km
Estimated by rail
Travel Time
~1h 2m
Express
CO2 Saved vs Flight
82.6%
22.4 kg less CO2
Environmental Comparison
Train
Express
CO2 Emissions
4.7 kg
Flight
Economy class
CO2 Emissions
27.2 kg
Taking the train saves 22.4 kg CO2 (82.6% less emissions)
Route Information
High-Speed
Requires Transfer
Stations on This Route
Continue Your Journey
Continue from Portsmouth Harbour
Also from London St Pancras International
Frequently Asked Questions
The estimated train journey from London St Pancras International to Portsmouth Harbour takes approximately 1h 2m. This estimate is based on a rail distance of ~139 km using a express service.
The estimated rail distance from London St Pancras International to Portsmouth Harbour is approximately 139 km (107 km straight-line). Rail routes are longer than straight-line distances because tracks follow terrain and connect intermediate cities.
Travelling by train from London St Pancras International to Portsmouth Harbour emits approximately 4.7 kg of CO2, compared to 27.2 kg by flight. Taking the train saves 22.4 kg of CO2 — a 82.6% reduction in emissions.
The route from London St Pancras International to Portsmouth Harbour typically requires at least one transfer. Check operator timetables for the most direct connection available.
Check regional and national rail operator websites for services between London St Pancras International and Portsmouth Harbour.
Train vs Flight comparison
Compare door-to-door time, CO2 and cost for London St Pancras International to Portsmouth Harbour
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Data last updated: 2026-02-27