Frequently asked
How is distance calculated?
Great-circle distance using the Haversine formula on the WGS84 reference ellipsoid (mean radius 3440 nm). The result is the shortest distance over the surface between two points; actual passage distance is longer when you follow rhumb-line tracks for ease of navigation, route around weather or ice, or take traffic-separation schemes. The estimator returns ±2-3% of typical commercial routing distance for most port pairs.
How is passage time computed?
Passage time = distance ÷ speed. Speed is measured at sea, not in port. Add port stays (typically 12-48 hours per call) on top of the cumulative steaming time. The plan includes anchorage time at the destination if you set 'arrival anchor hours'.
Why do my ports not show?
Type at least 3 characters of the port name or UN/LOCODE. The picker matches against ports.json (17,600+ ports). UN/LOCODE is the fastest match — try SGSIN for Singapore, NLRTM for Rotterdam, USNYC for New York. The autocomplete is case-insensitive.
Does this account for canal transits or weather routing?
No — this is a straight great-circle estimator. For Suez, Panama, or other canal routings, build the voyage as a multi-leg with the canal entrance and exit as waypoints (e.g. EGSUZ then EGPSE for a Suez transit). For weather routing, use a dedicated commercial product (StormGeo, AWT, ARM) or your operator's voyage-planning system.
Voyage planner
Enter ports by UN/LOCODE or name (e.g. SGSIN, NLRTM, USNYC) to plan a multi-leg voyage. Distances are great-circle, in nautical miles. Passage time = distance ÷ speed. Add port-stay hours between legs to estimate total ETA.
Voyage legs
Method: Haversine on WGS84 (mean radius 3440 nm). For routing through canals or other waypoints, add the canal entry and exit ports as legs (e.g. EGSUZ + EGPSE for Suez). See single-leg distance calculator, passage planning reference.