Home / Toolbox / Units on the water
Converting nautical miles, cable lengths, fathoms and chart measurements
Converting measurements starts here: a nautical mile is 1,852 metres,
one minute of arc on a great circle.
A cable is a tenth of that, a fathom 1.829 metres.
Calculator
The nautical mile is not an arbitrary unit but one minute of arc on the globe. That is why you can measure distances directly on any chart, using the latitude scale. Cable lengths turn up in harbour information and fathoms for depths on older charts, and you still come across them on British and American charts today.
For insurance contracts, nautical miles are the language of cruising ranges. Limits are described in nautical miles from the coast, twelve-mile zones define coastal waters, and extensions of cover state radii in nautical miles around a given point. If you cannot convert the unit, you cannot check your cruising range.
That is more than theory: a passage that crosses the agreed limit is not covered. Some policies allow a worldwide cruising range with no time limit and no geographical restriction, and anyone who chooses one need never do the sums. Where the range is limited, it is worth reading the exact wording before you cast off.
Frequently asked questions
How many kilometres is a nautical mile?
1.852 kilometres.
It corresponds to one minute of arc on a great circle.
What happens if I go beyond the cruising range?
Outside the agreed range there is no cover.
Some insurers offer a worldwide cruising range with no restrictions;
check the cruising area stated in your policy.
Worked out for your type of boat
Related
5,034 customer reviews, aggregated on Trustami
99.28 % positive, each with a name and date: Ausgezeichnet.org, Kundennote and Google
More from “Navigation and planning”
