40 mph to kn — 40 miles per hour in knots
Exact 40 ÷ 1.150779 = 34.75905
40 miles per hour in other units
| Metres per second | 17.8816 | m/s |
|---|---|---|
| Kilometres per hour | 64.37376 | km/h |
| Feet per second | 58.666667 | ft/s |
| Knots | 34.75905 | kn |
mph to kn at a glance
| Miles per hour | Knots |
|---|---|
| 1 mph | 0.86897624 kn |
| 2 mph | 1.737952 kn |
| 3 mph | 2.606929 kn |
| 5 mph | 4.344881 kn |
| 10 mph | 8.689762 kn |
| 20 mph | 17.379525 kn |
| 25 mph | 21.724406 kn |
| 50 mph | 43.448812 kn |
| 100 mph | 86.897624 kn |
| 250 mph | 217.24406 kn |
| 500 mph | 434.488121 kn |
| 1,000 mph | 868.976242 kn |
How to convert miles per hour to knots
Multiply by 0.86897624 — one mile per hour is 0.86897624 knots. That factor is exact: it comes from the definition of the units rather than from a measurement, so it will not change and does not need rounding.
Working 40 ÷ 1.150779 = 34.75905
In words: about thirty-five knots.
Questions
How many knots are in a mile per hour?
One mile per hour is 0.86897624 knots. This figure is exact — it comes from the definition of the unit, not a measurement.
What is 40 miles per hour in knots?
40 miles per hour is 34.75905 knots. The working is 40 ÷ 1.150779 = 34.75905.
What is a knot?
One nautical mile per hour — and a nautical mile is one minute of latitude, fixed at exactly 1,852 metres. That is the whole point of it: a ship making 10 knots for six hours has covered one degree of latitude, which you can read straight off a chart without converting anything.
Why do sailors and pilots say "knots" and not "knots per hour"?
Because the "per hour" is already inside the word. A knot is a speed, not a distance, so "knots per hour" would be an acceleration. The name comes from the knotted rope once paid out behind a ship and counted against a sand glass.
What's the quick way to convert mph to km/h in my head?
Multiply by 1.6, or add 60%. For the other direction, take away a third and then a little more. Fifty mph is 80 km/h, 60 is 97, 70 is 113 — worth remembering if you drive across a border where the signs change.
Why isn't Mach on this page?
Because it is not a fixed unit. Mach 1 is the local speed of sound, which falls as air gets colder — around 1,235 km/h at sea level but closer to 1,062 km/h in the stratosphere where airliners cruise. A single conversion factor would be wrong nearly everywhere.