Calculate sea travel time between ports based on distance in nautical miles and vessel speed in knots. Plan ferry, cruise, and sailing trips accurately.
Whether you're planning a ferry crossing, a cruise leg, a sailing charter, or a long ocean voyage, knowing the travel time by sea is essential. Sea travel is measured in nautical miles (1 NM = 1.852 km) and speed in knots (1 knot = 1 NM/hour).
This calculator converts nautical distance and vessel speed into total travel time. Different vessel types travel at very different speeds: a modern car ferry cruises at 18–25 knots, a large cruise ship at 20–24 knots, a sailboat at 5–8 knots, and a powerboat at 15–30+ knots.
Sea travel times also depend on weather and sea conditions. Headwinds and rough seas can reduce effective speed by 10–30%. Planning with realistic speeds prevents missing port reservations, accommodation check-ins, or connecting transport. Whether you are a beginner or experienced professional, this free online tool provides instant, reliable results without manual computation. By automating the calculation, you save time and reduce the risk of costly errors in your planning and decision-making process.
Sea travel speed varies enormously by vessel type and conditions. This calculator converts distance and speed into hours and days, helping you plan port departures, ferry bookings, and cruise shore excursions. Having a precise figure at your fingertips empowers better planning and more confident decisions. Manual calculations are error-prone and time-consuming; this tool delivers verified results in seconds so you can focus on strategy.
Travel Time (hours) = Distance (NM) / Speed (knots) Speed Adjustment = Base Speed × (1 − Weather Penalty) Weather penalties: Calm = 0%, Moderate = 10%, Rough = 25%
Result: 25 hours (1 day 1 hour)
A 450 nautical mile ferry route at 20 knots takes 22.5 hours in calm seas. With a 10% speed reduction for moderate seas, the effective speed is 18 knots, giving 25 hours travel time — just over 1 day.
Dover to Calais: 21 NM (1–1.5 hours by ferry). Athens to Santorini: 120 NM (5–8 hours). Southampton to New York: 3,100 NM (5–7 days by ship). Sydney to Auckland: 1,150 NM (2–3 days). These distances help benchmark your own route.
Ferries are the fastest scheduled option (18–45 knots). Cruise ships prioritize comfort over speed (20–24 knots). Sailing is the slowest but most adventurous (5–8 knots average). Choose based on your budget, time, and experience goals.
Overnight ferries are excellent time-savers on routes of 8–14 hours. You travel while sleeping, arriving fresh at your destination. Book a cabin with a bed rather than sleeping in a reclining chair for actual rest.
A nautical mile is 1.852 km (1.151 statute miles). It's based on one minute of latitude arc, making it naturally useful for sea and air navigation. Charts and maritime distances are always given in nautical miles.
A knot is one nautical mile per hour. The term comes from the old practice of measuring ship speed by counting knots on a rope paid out behind the vessel over a fixed time. 20 knots = 37 km/h or 23 mph.
Kayak: 3–5 knots. Sailboat: 5–8 knots. Fishing boat: 8–12 knots. Car ferry: 18–25 knots. High-speed ferry: 35–45 knots. Cruise ship: 20–24 knots. Container ship: 14–18 knots. Naval vessel: 25–35+ knots.
Calm seas (Beaufort 0–2) have minimal effect. Moderate seas (Beaufort 3–5) can reduce speed 10–15%. Rough seas (Beaufort 6–7) reduce speed 20–30%. Severe conditions may require route changes or delays for safety.
Use online nautical charts or port-to-port distance calculators. Popular resources include MarineTraffic, Sea-Distances.org, and navigation apps like Navionics. These account for shipping lanes and coastal geography.
Yes, significantly on some routes. The Gulf Stream flows at 2–5 knots across the Atlantic. Traveling with the current adds those knots to your effective speed; against it, they subtract. This matters most for slower vessels on long voyages.