Sea distance between ports: route, passage time and fuel

An online calculation of sea distance between ports. It lays a route over water — round the continents and through the real straits and canals — and works out the passage time at a given speed, the fuel burn and its cost. The whole calculation runs in your browser: the land map and the place list are already loaded with the page, so there are no request limits, no queue and no dependence on someone else's server.

How to work it out

Choose the ports

Start typing a name — the search covers tens of thousands of places in your language. Or just click the map.

Set speed and consumption

Passage time, fuel and cost follow immediately.

Refine the route

Close a canal if it does not suit, and compare the options in miles.

Pick two ports and get a path that actually goes round the land

A calculation for planning and estimating, not a passage plan. The water-and-land grid has a step of about seven nautical miles, so the route is notional in narrow waters and on approaches. Soundings, currents, wind, traffic separation schemes, areas to be avoided, canal draught limits and ice are not allowed for. Passage planning is done on a corrected chart.

Features

The route is solved inside the page

Every sea-distance service we know of answers by round-tripping to a server, so each route costs a request and a wait. Here the land map is part of the page and the search runs on it: a route takes tens of milliseconds, and comparing a dozen variants is a matter of clicking.

Checked against passages you can verify

Rotterdam–New York 3255 miles, Rotterdam–Singapore 8301, Shanghai–Los Angeles 5722, Sydney–Valparaíso 6122. All within one and a half per cent of the published figures, and pinned by a test rather than checked once.

Canals can be closed

Suez and Panama switch off with a checkbox — for a queue, transit fees or the situation. The route reroutes round Africa or through the Magellan Strait, and the difference in miles is immediate.

Polar routes are off by default

There is no ice in the map, and without a latitude limit the router takes the ship up the Northern Sea Route: Rotterdam–Singapore with Suez closed came out at 9617 miles instead of over eleven thousand round Africa. High latitudes are closed by default and can be opened deliberately, with a warning.

The route is straightened, not left as a staircase

A raw grid path moves in 45° steps and comes out 4–7% longer than the straight line. Straight legs are pulled taut wherever the segment is entirely over water — both the distance and the line on the map become real, and a dozen points replace a hundred.

Waypoints and GPX

A table of legs with the course and length of each, and a GPX export for a plotter or planning software.

What you can do

Find the distance over water between any two ports
Work out the passage time at your own speed
Estimate the fuel burn and its cost
Compare a route through a canal with the way round
See the legs with the course and length of each
Export the route as GPX

Why the straight-line distance is no use for a passage

A straight line between two ports almost always crosses land, and the difference is not cosmetic. Rotterdam to Singapore is about 5,800 miles on the great circle and 8,300 over water through Suez: fifteen hundred miles apart, which is a week of steaming and hundreds of tonnes of fuel. The case with the canal closed is starker still — the same passage round Africa runs to over eleven thousand miles. Freight, bunkers and schedules are therefore reckoned on the distance OVER WATER; "as the crow flies" is good only for judging whether a region is reachable at all.

Frequently asked questions

How accurate are the distances?

On ocean passages, within one and a half per cent of published figures; that is checked by a test on six passages on every change. But the accuracy is bounded by the grid: a cell is about seven nautical miles, so in narrow waters, archipelagos and approaches the route is notional. This is a calculation for planning and estimating, not a passage plan.

Why does the route sometimes run oddly close to the shore?

Because the grid is coarse: the coastline is generalised to seven miles and the path follows water cells. The check refuses a route that cuts land — including a clip of a cell corner — but there is no safe offing here and cannot be: that needs a chart with soundings.

How are the straits handled?

By an explicit list. At a seven-mile step Gibraltar, eight miles wide, closes after generalisation, and the Bosphorus all the more, so the known straits and canals are carved separately and named: Gibraltar, Suez, Panama, Bosphorus, Dardanelles, Kerch, the Kiel Canal, the Danish straits, Dover, Messina, Bab-el-Mandeb, Hormuz, Malacca, Singapore, Sunda, Lombok, Torres, Magellan, Cook, Bering and others. The list is incomplete and will grow.

Why are polar routes switched off?

Because there is no ice in the map. Without a latitude limit the router happily takes a ship up the Northern Sea Route all year round — it genuinely is shorter, and that is the danger: the result looks convincing. The limit is lifted with a checkbox, and then a warning appears beside the result.

Are currents, wind and prohibited areas allowed for?

No. This is the geometry of water and land and nothing more. Traffic separation schemes, areas to be avoided, war-risk zones and canal draught limits are not in it. Any one of them can change a route more than everything computed here.

Where do the ports come from?

From the same place set the rest of the site uses: about thirty-four thousand settlements with names in ten languages (GeoNames, CC BY 4.0). A point is snapped to the nearest water, so a river port a few miles inland is found too. If a place is missing, click the map.

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Who is this tool for?

⚓ Sailors and yacht crews

Published 01 Sep 2026 Updated 02 Sep 2026 Author: The Supreme