How the sea distance calculator works
Ships cannot sail a straight line between two ports: continents, capes and shallow water force them through a handful of chokepoints. The calculator models that with a network of about 120 waypoints placed on the real shipping lanes: the Strait of Malacca, the Luzon and Taiwan straits, Bab-el-Mandeb, both ends of the Suez Canal, Gibraltar, Ushant and the English Channel, the Cape of Good Hope, both ends of the Panama Canal, the Windward Passage, the Strait of Juan de Fuca and more. Each leg between waypoints is a great-circle arc, and the tool finds the shortest chain of legs between the two ports.
- Distance is in nautical miles (1 nm = 1.852 km), the unit every voyage plan and charter party uses.
- Time at sea is distance divided by speed × 24, plus about a day for each canal transit and its waiting time.
- Typical scheduled transit widens that to allow for the port calls, transhipment and schedule slack built into liner services. It is a planning range, not a schedule: use your carrier's sailing schedule for bookings.
- Route options show what happens if the Red Sea and Suez Canal are avoided (around the Cape of Good Hope, as most Asia–Europe services did from 2024) or if the Panama Canal is avoided.
Formula
Container lines have run "slow steaming" speeds of about 14–18 knots for over a decade to save fuel, well below the 22–25 knots the ships are designed for. Bulk carriers and tankers typically cruise at 12–15 knots. Use 16 knots for liner planning unless your carrier says otherwise.
Distances on the main trade lanes
| Lane | Shortest, nm | Days at 16 kn | Avoiding Suez, nm | Shortest via |
|---|---|---|---|---|
| Shanghai → Los Angeles / Long Beach | 5,729 | 14.9 | – | North Pacific |
| Shanghai → New York / New Jersey | 10,397 | 28.1 | – | Panama Canal |
| Shenzhen (Yantian) → Rotterdam | 9,855 | 26.7 | 13,334 | Strait of Malacca, Suez Canal |
| Shanghai → Felixstowe | 10,383 | 28.0 | 13,862 | Strait of Malacca, Suez Canal |
| Singapore → Rotterdam | 8,377 | 22.8 | 11,929 | Strait of Malacca, Suez Canal |
| Nhava Sheva (JNPT, Mumbai) → New York / New Jersey | 8,221 | 22.4 | 12,434 | Suez Canal |
| Shanghai → Sydney (Port Botany) | 4,594 | 12.0 | – | direct |
| Los Angeles / Long Beach → Sydney (Port Botany) | 6,514 | 17.0 | – | direct |
| Southampton → New York / New Jersey | 3,214 | 8.4 | – | direct |
| Rotterdam → New York / New Jersey | 3,431 | 8.9 | – | direct |
| Jebel Ali (Dubai) → Felixstowe | 6,137 | 17.0 | 11,351 | Suez Canal |
| Shanghai → Santos | 11,031 | 28.7 | – | Cape of Good Hope |
All figures above come from the same routing model as the calculator, so they agree with it exactly.
Worked example: Shanghai to Rotterdam, two ways
Through the Strait of Malacca, the Red Sea and the Suez Canal, the model gives 10,459 nm. At 16 knots that is 27.2 days of steaming plus a day for the canal, about 28 days at sea. Port Economics, Management and Policy puts the same route at about 10,600 nm and 27 days.
Avoiding the Red Sea and sailing round the Cape of Good Hope it is 13,939 nm, 3,479 nm more, which adds roughly 9 days at the same speed. That extra week and a half of sailing on every rotation is why carriers needed more ships when they diverted, and why freight rates and transit times rose. Carriers began moving services back through Suez during 2026, so the shortest route is the default; tick the option to see the diversion.
Mistakes when planning by distance
- Mixing up miles. A nautical mile is 1.15 statute miles. A distance read as statute miles is 15 % too short.
- Treating days at sea as transit time. Door-to-door ocean freight adds trucking, terminal cut-off, the vessel's other port calls, transhipment, discharge, customs and delivery. Two to three weeks of sailing is commonly four to six weeks door to door.
- Assuming direct services. Many lanes, especially to Africa, South America and smaller ports, transship at a hub such as Singapore, Colombo, Algeciras or Jebel Ali, adding days and handling.
- Ignoring canal limits. The largest container ships are too big for the Panama Canal, and the canal restricts draught in dry seasons. Asia–US East Coast services may route via Suez instead.
- Planning on the best case. Port congestion, weather and blank sailings can add a week or more. Build buffer stock around peak season and Chinese New Year.
Questions shippers ask
How do I calculate the distance between two ports?
Use a routing tool like this one, which follows shipping lanes, or a published port distance table. A straight great-circle line between the two ports is always too short because it crosses land.
How many days does it take to ship from China to the USA by sea?
Shanghai to Los Angeles is about 5,700 nm, roughly 15 days at sea at 16 knots and typically 17–24 days on a liner schedule. To New York via the Panama Canal it is about 10,400 nm and 28 days at sea. See the China to USA guide for door-to-door times.
What is a knot?
One nautical mile per hour, 1.852 km/h. A ship at 16 knots covers 384 nautical miles, about 711 km, a day.
How much longer is the route around the Cape of Good Hope?
For Shanghai to Rotterdam, about 3,500 nm or 9 days at 16 knots. For ports in the Middle East, India and the eastern Mediterranean the penalty is proportionally much larger because Suez is so close to them.
Are the distances exact?
No. They are modelled along a waypoint network and fall within a few per cent of published distance tables on the main lanes. Real voyages vary with weather routing, traffic separation schemes and pilot stations.
Sources
Rules checked: November 2026 Distances are modelled on a waypoint network and checked against published figures (within about 3 % on the main lanes). Canal availability and carrier routings change; check your carrier's schedule.
Rates, fees and the rule pages behind this tool are checked automatically twice a week; last check 3 November 2026.
- Port Economics, Management and Policy: routing options between Shanghai, Rotterdam and New York — about 10,600 nm via Suez and 13,800 nm via the Cape
- Suez Canal Authority
- Panama Canal Authority: vessel requirements and draught restrictions
- Seatrade Maritime: full Suez return for container carriers expected by Q1 2027