Conversion formula

The conversion factor from miles per hour to knots is 0.8689762419014, which means that 1 mile per hour is equal to 0.8689762419014 knots:

1 mph = 0.8689762419014 kt

To convert 21 miles per hour into knots we have to multiply 21 by the conversion factor in order to get the velocity amount from miles per hour to knots. We can also form a simple proportion to calculate the result:

1 mph → 0.8689762419014 kt

21 mph → V_(kt)

Solve the above proportion to obtain the velocity V in knots:

V_(kt) = 21 mph × 0.8689762419014 kt

V_(kt) = 18.248501079929 kt

The final result is:

21 mph → 18.248501079929 kt

We conclude that 21 miles per hour is equivalent to 18.248501079929 knots:

21 miles per hour = 18.248501079929 knots

Alternative conversion

We can also convert by utilizing the inverse value of the conversion factor. In this case 1 knot is equal to 0.054799021334407 × 21 miles per hour.

Another way is saying that 21 miles per hour is equal to 1 ÷ 0.054799021334407 knots.

Approximate result

For practical purposes we can round our final result to an approximate numerical value. We can say that twenty-one miles per hour is approximately eighteen point two four nine knots:

21 mph ≅ 18.249 kt

An alternative is also that one knot is approximately zero point zero five five times twenty-one miles per hour.

Conversion table

miles per hour to knots chart

For quick reference purposes, below is the conversion table you can use to convert from miles per hour to knots