Knots to Miles per Hour Converter | knot to mph

What this converter does

Knots turn up on boat instruments, in aircraft figures, and all through marine and aviation weather, and if you do not spend your days around those, the number can feel abstract. This converter turns a speed in knots into the miles per hour you live by on the road, so you can feel how fast it really is. Enter the knots and read off the mph.

The conversion factor

One knot is one nautical mile per hour, and a nautical mile is a little longer than a land mile, so one knot works out to 1.15078 mph:

mph = knots × 1.15078

That means the mph figure always comes out a bit higher than the knots you started with, because each nautical mile covers slightly more ground than a statute mile.

A quick estimate

The factor is close to 1.15, so for a quick figure, add about 15 percent to the knots value. Take 20 knots, 15 percent of that is 3, so roughly 23 mph, and the exact answer is 23.0 mph, which is bang on. Remembering that knots run a little higher when you put them into mph is usually enough to picture the speed without reaching for anything.

A worked example

Say a boat is cruising at 22 knots and you want that in everyday terms.

• 22 × 1.15078 = 25.3 mph

So 22 knots is about 25.3 mph. Put like that, you can feel it as a brisk speed on the water, a touch quicker than a car easing through a built-up area, which is far easier to picture than the bare knot figure on the dial.

Common knots in mph

For a feel, 10 knots is around 11.5 mph, and a 40 knot gale comes in near 46 mph.

Where you meet knots

Sailors and powerboaters read their speed over water in knots, so converting helps anyone used to road speeds judge how a boat is moving. Aviation runs on knots too, for airspeed and ground speed, which is why a plane's figures often need translating for a passenger's sense of things. And weather is a big one: wind in marine and aviation forecasts is given in knots, and storm reports, including hurricane wind speeds, are frequently quoted that way, so turning them into mph makes the strength of a wind land properly. Any time a knot figure needs to mean something to someone who thinks in miles per hour, this is the conversion.

One thing to get right

A small point that trips people up: a knot already means one nautical mile per hour, so the speed is just knots, never knots per hour. Saying knots per hour would actually describe a change in speed over time, which is a different thing entirely. So a boat does 22 knots, not 22 knots per hour. It is a tiny habit, but getting it right marks the difference between sounding at home on the water and not.

Questions people ask

How do I convert knots to mph?

Multiply the speed in knots by 1.15078. For a quick estimate, add about 15 percent to the knots figure.

What is 20 knots in mph?

About 23 mph. It is a clean one to remember, since adding 15 percent to 20 lands you right on the exact figure.

Why is the mph number bigger than the knots?

A nautical mile is longer than a land mile, so each knot covers a bit more distance per hour than a mile per hour does, making the mph figure higher.

References

1. National Institute of Standards and Technology (NIST), Special Publication 811, Guide for the Use of the International System of Units (unit conversion factors). https://www.nist.gov/pml/special-publication-811
2. National Oceanic and Atmospheric Administration (NOAA), National Ocean Service, What is the difference between a nautical mile and a knot? https://oceanservice.noaa.gov/facts/nautical-mile-knot.html