Speed, time & distance. In the form the exam asks.

60 × D = S × T, where D is distance in nautical miles, S is speed in knots, and T is time in minutes. It is the same relationship as distance = speed × time, rearranged so you can work in minutes instead of decimal hours — which is how Coast Guard problems are posed and how you would time a leg in the wheelhouse. Cover the quantity you want and the remaining two show whether to multiply or divide: D = S × T ÷ 60, S = 60 × D ÷ T, T = 60 × D ÷ S.

Because that is the form the exam asks in. A question gives you '2 hours 45 minutes', not '2.75 hours', and expects an answer in the same shape. Converting to decimals and back is two extra chances to slip. The commonest error on this material is mixing the forms — putting minutes into the plain D = S × T, which wants hours, and landing 60 times out. This calculator takes hours and minutes and shows the decimal equivalent alongside so you can cross-check either way.

Find the run time for the leg, then add it to your departure time on the 24-hour clock. Enter a departure time above and the calculator does it, and — importantly — tells you when the arrival crosses midnight into the next day. An ETA of 0300 means very different things depending on whether it is tonight or tomorrow, and a tool that prints the clock time alone invites exactly that mistake.

A nautical mile is 1,852 metres — one minute of latitude, which is what makes it useful: you measure distance off a chart against the latitude scale on the side, not against a separate distance scale. A knot is one nautical mile per hour. Statute miles (5,280 feet) are for road signs; charts, speeds and the exam all use nautical. If you have a distance in statute miles, convert before you start.

No. This is speed through the water against distance run — the dead-reckoning relationship. Set and drift from current, and leeway from wind, are applied separately to get your speed over ground and course made good. Solve the leg here first, then apply the current triangle; do not try to fold them into one step.