Ocean Miles Calculator
Knots, miles and hours at sea, worked out in your browser.
Get a Free Cruise QuoteOcean Miles Calculator: Knots, Miles and Time at Sea
Use this ocean miles calculator to turn a ship’s speed into miles per hour, to work out how long a passage takes, and to see how far a ship can sail in a day. Everything runs in your browser; change any box and the answers update.
Speed converter
= 23.0 mph = 37.0 km/h
Passage time
at
Time at sea: 13 h 20 min (240 nautical miles)
Distance in a day
At for : 480 nautical miles = 552 statute miles = 889 km
How the Calculator Works
- Speed: knots × 1.1508 gives mph; knots × 1.852 gives km/h.
- Passage time: distance in nautical miles ÷ speed in knots gives hours. Statute miles and kilometers are converted to nautical miles first.
- Distance in a day: speed in knots × hours under way gives nautical miles.
The conversion factors come from the definitions published by NOAA Ocean Service. Results are rounded.
What the Calculator Cannot Tell You
Real passages are rarely a straight line at a steady speed. Ships slow down leaving and entering port, follow traffic lanes and pilotage rules, steer around weather, and sometimes wait offshore for a berth or a pilot. The captain also plans a margin, so the ship can arrive on time even if conditions change. Use the calculator for a feel for the numbers, not as a timetable.
Try These Examples
- A typical overnight Caribbean hop: put in a distance of 150 to 250 nautical miles at 14 to 18 knots and see why many ships arrive at breakfast time.
- A transatlantic crossing: about 3,150 nautical miles from Southampton to New York, which The Man in Seat 61 gives for the seven-night Queen Mary 2 crossing. Over roughly 160 hours, that works out at close to 20 knots on average, even though the ship can sail much faster.
- A sea day: 20 knots for 24 hours is 480 nautical miles, a little over 550 statute miles.
See miles per sea day for more on daily distances.
Using the Numbers When You Choose a Cruise
The calculator is more than a curiosity. When two itineraries visit similar ports, the one with longer legs between them will usually mean more sea days, earlier all-aboard times or a faster overnight passage. Plug in a rough distance between two ports and the ship’s likely speed, and you can see whether a port day is likely to be long and relaxed or short and rushed. If you are prone to seasickness, longer open-sea legs are worth knowing about in advance, and a mid-ship cabin on a lower deck may suit you better.
Distances between ports are not always printed in cruise brochures, but our cruise advisors at Mister Cruise can check them for any itinerary you are considering, along with arrival and departure times.
Plan a Voyage With the Right Number of Sea Days
Tell us whether you want long lazy sea days or a port every morning. Our cruise advisors at Mister Cruise will find the itinerary. Free.
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