Time, Speed, and Distance
Time, speed, and distance are related by the formula:
distance = speed x time. Therefore, if any two of the three quantities
are known, the third can be found. The units must be consistent. (The
distance scales on nautical charts use nautical miles and yards, unless
otherwise stated on the chart. A nautical mile is equal to 2,000 yards.)
Thus, if speed is measured in knots and time in hours, the answer is in
nautical miles. Similarly, if distance is measured in nautical miles and
time in hours, the answer is in knots. If distance is measured in yards
and time in minutes, the answer is in yards per minute.
Table 19 of Bowditch is a speed, time, and distance table that supplies
one of the three values if the other two are known. It is intended
primarily for use in finding the distance steamed in a given time at a
The following formulas may be used if the speed is measured in knots,
the distance in nautical miles, and the time in hours and/or tenths of
hours (0.1 hour = 6 minutes).
Distance = Speed x Time
Speed = Distance ÷ Time
Time = Distance ÷ Speed
Example 1. Your ship steams for a period of 4 l/2 hours and covers a
distance of 54 nautical miles. What is your speed?
S= 12 knots
In example 1, time was given in hours and tenths. When time is given
or required in minutes, the same formulas, slightly changed, are still