Free online tools for marine engineers, vessel operators, and maritime developers.
This page brings together our free online marine tools — a hand-built collection for vessel operators, marine engineers, navigators, and maritime developers. Decode AIS and NMEA sentences, validate IMO and MMSI numbers, convert GPS coordinates between formats, compute great-circle distance and bearings, estimate tide heights with the Rule of Twelfths, and inspect NMEA 2000 PGN data — all directly in your browser, with no registration and nothing sent to a server.
Whether you're parsing NMEA 0183 logs from a chartplotter, reverse-engineering a raw N2K CAN bus capture, validating a ship's MMSI for AIS broadcast, or working out the bearing and distance between two waypoints, the 17 tools below cover the everyday calculations that marine software, surveyors, and bridge crews need.
$GPGGA, $GPRMC, and $IIMWV report position, heading, depth, wind, and more.!AIVDM NMEA sentences with a 6-bit ASCII-armored payload.