A sea distance API answers one question programmatically: how far is it from port A to port B by water, along a route a vessel could actually take. Freight calculators, logistics platforms, emissions estimators, and booking tools all need it, and a handful of providers sell it at very different prices. This guide compares the sea route APIs available in 2026, what each returns, and what the numbers cost.
Disclosure up front: Marine OS sells one of the APIs below. The comparison stays factual, and the underlying method, routing over a maritime network graph, is the same across the industry.
- Sea distances are computed as shortest paths over a maritime network of shipping lanes, not straight lines.
- Enterprise providers such as Searoutes list from roughly 400 EUR per month; several were built for freight and emissions teams.
- The Marine OS Route API returns distance, voyage time, passages, and GeoJSON geometry at $799 per month billed annually.
- For occasional lookups, free web pages cover known routes without an API at all.
#How every sea distance API works
Under the hood, all of these products do the same thing: maintain a graph of maritime routes (nodes at sea, edges along shipping lanes, special edges for canals and straits), snap your origin and destination onto the graph, and run a shortest-path search with your constraints, such as avoiding Suez or Panama. The differences are the network quality, the constraints exposed, the extras (voyage time, emissions, geometry), and the price.
#Searoutes
Searoutes is the reference enterprise provider, aimed at freight forwarders and shippers who need routing plus CO2 emissions methodology. Its routing API is mature and the emissions angle is the differentiator. Published entry pricing has been in the region of 400 EUR per month, with plans scaling from there.
#SEAMETRIX
SEAMETRIX sells a sea distances API popular with chartering and operations teams, with unlimited-style plans typically quoted per year. It focuses on distance and time between the world port pairs rather than a broader logistics suite.
#Datalastic and AIS-centric providers
Datalastic and similar vendors approach the problem from vessel-tracking data: their strength is AIS positions and vessel movements, with sea-route endpoints alongside. If you need live ship tracking plus distances in one subscription, this category fits, priced per month by request volume.
#Marine OS Route API
The Marine OS Route API computes port-to-port routes over the open Eurostat global shipping-lane network. One GET request returns distance in nautical miles, kilometers and statute miles, voyage time at your speed, the canals and straits the route uses, and optional GeoJSON geometry. Sixteen passages can be excluded per request, from Suez and Panama to the Northwest Passage. Pricing is $1,199 per month, or $799 per month billed annually, with 10,000 calls included, and a free 100-call trial key by email. The honest scope: planning-grade distances of the kind freight tools publish, not weather-routed voyage plans.
Before subscribing anywhere, test known routes: Rotterdam to Singapore should land near 8,400 nm via Suez, Shanghai to Los Angeles near 5,700 nm, and New York to Los Angeles near 4,900 nm via Panama. A provider that cannot reproduce known distances within a few percent is not worth any price.
#When you do not need an API at all
If you need a handful of distances rather than programmatic access, published route pages cover the common pairs at no cost, including our own sea distance pages computed by the same engine as the API. Spreadsheets with occasional lookups rarely justify a subscription.
Marine OS is marina management software, and the same routing engine that powers our boater route planner is available to developers as the Route API. One founder-run stack, priced far below the enterprise incumbents.
Port-to-port distances in one GET request
Distance, voyage time, passages, and route geometry over the global shipping-lane network. $799/mo billed annually, or $1,199 monthly, with a free trial key by email.
#Frequently asked questions
Frequently asked questions
Pick by what you need beyond the number: emissions methodology, AIS tracking, or plain fast distances at sane pricing. For the last one, see the Route API docs, and for human-readable numbers, the sea distance pages.
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