From nautical miles to mph? That’s how fast your boat really goes


Give or treat yourself to a subscription to Boats in Motion print + digital and for only 39 euros a year you get the magazine at home plus read it on your PC, smartphone and tablet. With a sea of advantages.

SPX 24 – Archive photo – From knots to km/h

Knots to km/h. Many of our readers will surely already know the differences in the case. For the many newcomers to boating now, units of measurement can be confusing.

So here is an easy-to-understand vademecum for clarity between nodes, nautical miles, mph and km/h.

For velocity, the formula is always the same:



t. Velocity = space/time.

First consideration. On the road we are used to kilometers per hour. When we are at sea the reference is knots, almost all over the world(we explain why at the end of the article!). In the US we often use miles: land or nautical?

Let’s look at all the relevant differences and what knots (kn), kilometers per hour (km/h) miles per hour (mph) and nautical miles (nm) correspond to.

You might be interested in:
the 3 superstitions of boaters, here’s their history

From knots to km/h

For boat speed, the unit of measurement is the same all over the world or nearly so. Traveling at a speed of 1 kn – 1 knot – is equal to traveling 1 nm, 1 nautical mile, an international symbol of Anglo-Saxon origin (nautical miles= nm). At 1 knot we complete 1 nautical mile in the time of 1 hour.

1 nautical mile (1 node) is equivalent to 1.852 km

Doing a quick calculation and translating it into an automotive measurement, a boat sailing at 30 kn is going 55.5 km/h. How did we do it? 30 x 1.852 = 55.5.

At 30 knots it will then travel 30 nautical miles in one hour.

Americans sometimes “get smart” and we may be faced with instrumentation in land miles(1 mph – 1.60934 km). So a U.S. boat traveling at 40 mph (miles per hour) is sailing at 34.8 knots or 34.8 nm, nautical miles.

How to go from land miles to nautical miles?

For us, the conversion is quickly done; simply multiply by 0.87. The result is equivalent in nautical miles or knots. The difference lies in what you have to calculate: a distance or a speed.

Read all the articles on boating license 2024 here

Knots to km/h. How many is 12 nautical miles in kilometers?

When you are about to get your boating license you are faced with an initial, it must be said, fundamental watershed. In addition to figuring out whether you want to do sailing, motor, or both, another option concerns the type of license. Boat license within or beyond 12 miles? If you are not yet familiar with nautical miles here is what it corresponds to: 12 miles is about 22.22 km. A rather considerable distance, therefore, from the coast.

Sea miles and knots

What is a node? Cruising at the speed of one knot means in practice completing one nautical mile (which is equivalent to 1.852 kilometers) within one hour.

Suzuki’s powerful license-free outboard! Watch the video

Why is boat speed measured in knots? History

In ancient times, electronics were not there. To understand speed back then, the tool for measuring the knots that passed through the hands of the sailor was called a solcometer. In fact, they unrolled a long line with knots to which a piece of wood was tied. Inodes were at a distance of 15.433 meters from each other. That is, the path a boat would take in 30 seconds if it traveled one nautical mile every hour:

15.433 m/30” x 3600 =1852 = 1 node
So each node passing in the thirty seconds corresponded to a speed node.



Leave a Comment

Your email address will not be published. Required fields are marked *

Are you already a subscriber?

Sign up for our Newsletter

Join the Sailing Newspaper Club

Powerboats, its stories, from small open to motoryachts. Sign up now for our free newsletter and receive the best news selected by the editorial staff each week. Enter your email below, agree to the Privacy Policy and click the “sign me up” button.

Once you click on the button below check your mailbox



You may also be interested in.