Free tool
Sea distance calculator
Distance by ship between any two ports — in nautical miles, kilometers, and statute miles — computed over real shipping lanes, not a straight line. Set your speed for voyage time, and route around the Suez or Panama Canal to compare options. Free, no account required.
Distances are computed over the global shipping-lane network. Planning estimates only - not for navigation.
Real sea lanes
Routes follow the global shipping-lane network around coastlines and through canals and straits — the calculator names each passage the route uses.
1,600 world ports
Search by port name or UN/LOCODE — Shanghai (CNSHA), Singapore (SGSIN), Rotterdam (NLRTM) — or enter raw coordinates for any point at sea.
Voyage time & fuel
Set speed in knots for days-and-hours steaming time, then add your fuel burn and price for a quick voyage fuel estimate.
Popular port-to-port distances
Precomputed reference distances over the same network. Open any route for the full breakdown.
| Route | Distance | At 10 kn | |
|---|---|---|---|
| Algeciras to Apapa | 3,205 nm | 13d 9h | Details |
| Algeciras to Auckland | 11,295 nm | 47d 2h | Details |
| Algeciras to Busan | 9,601 nm | 40d 0h | Details |
| Algeciras to Cape Town | 5,142 nm | 21d 10h | Details |
| Algeciras to Chennai (ex Madras) | 5,763 nm | 24d 0h | Details |
| Algeciras to Colombo | 5,465 nm | 22d 19h | Details |
| Algeciras to Durban | 5,953 nm | 24d 19h | Details |
| Algeciras to El Iskandariya (Alexandria) | 1,847 nm | 7d 17h | Details |
| Algeciras to Fremantle | 8,488 nm | 35d 9h | Details |
| Algeciras to Genova | 858 nm | 3d 14h | Details |
Frequently asked
Is this sea distance calculator free?
Yes — 5 lookups per day, no account required. Pick any two of ~1,600 world seaports (or enter coordinates) and get the distance in nautical miles, kilometers, and statute miles, plus voyage time at your speed. Need more? The Route API starts at $49/month.
How is the distance calculated?
Routes are computed over the global shipping-lane network — the same open maritime network used in freight routing — so the distance follows real sea lanes around coastlines, through canals and straits, not a straight line on the map.
Why is the sea distance longer than the straight-line distance?
Ships cannot sail through land. A voyage from Shanghai to Rotterdam, for example, runs through the Strait of Malacca and the Suez Canal — thousands of miles longer than the great-circle line. The calculator shows which canals and straits each route uses.
Can I route around the Suez or Panama Canal?
Yes. Tick "Avoid Suez Canal" or "Avoid Panama Canal" and the route is recomputed around the Cape of Good Hope or Cape Horn, so you can compare distances and days for both options.
How is voyage time calculated?
Time = distance in nautical miles ÷ speed in knots. At 12 knots a vessel covers 288 nm per day, so a 7,200 nm leg takes about 25 days of steaming. Port time, weather, and currents are extra.
Is there an API for sea distances and voyage estimation?
Yes. The Marine OS Route API returns port-to-port distances, routes as GeoJSON, and full voyage estimates (bunker consumption and cost, TCE, voyage result) over HTTPS. See the Route API page for documentation and trial keys.
Need distances in your own system?
The Route API returns port-to-port distances, GeoJSON routes, and full voyage estimates — bunker consumption and cost, TCE, voyage result — over simple HTTPS calls. Built for chartering desks, freight platforms, and voyage-estimation tools.