991 miles per hour in knots

Conversion

991 miles per hour is equivalent to 861.155455723542 knots.^[1]

Conversion in the opposite direction

The inverse of the conversion factor is that 1 knot is equal to 0.0011612305227281 times 991 miles per hour.

It can also be expressed as: 991 miles per hour is equal to $\frac{1}{0.0011612305227281}$ knots.

Approximation

An approximate numerical result would be: nine hundred and ninety-one miles per hour is about eight hundred and sixty-one point one five knots, or alternatively, a knot is about zero times nine hundred and ninety-one miles per hour.

Units involved

This is how the units in this conversion are defined:

Miles Per Hour

"Miles per hour (abbreviated mph, MPH or mi/h) is an imperial and United States customary unit of speed expressing the number of statute miles covered in one hour. Although kilometres per hour is now the most widely used measure of speed, miles per hour remains the standard unit for speed limits in the United States, the United Kingdom, Antigua & Barbuda and Puerto Rico, although the latter two use kilometres for long distances."

Wikipedia page of miles per hour

Knots

"The knot (/nɒt/) is a unit of speed equal to one nautical mile (1.852 km) per hour, approximately 1.151 mph. The ISO Standard symbol for the knot is kn. The same symbol is preferred by the IEEE; kt is also common. The knot is a non-SI unit that is accepted for use with the SI. Worldwide, the knot is used in meteorology, and in maritime and air navigation—for example, a vessel travelling at 1 knot along a meridian travels approximately one minute of geographic latitude in one hour. Etymologically, the term derives from counting the number of knots in the line that unspooled from the reel of a chip log in a specific time."

Wikipedia page of knots

Footnotes

[1] The precision is 15 significant digits (fourteen digits to the right of the decimal point).

Results may contain small errors due to the use of floating point arithmetic.