Convert Knots to Miles Per Hour

A knot is a rate of speed used to determine how many nautical miles per hour something is travelling. This measurement is usually used to measure distances over the sea, and so it is helpful to convert knots to miles per hour, since this is a land rate most people better understand. The simplest way to convert knots to miles per hour is by multiplying the number of knots by 1.152.

Steps

Converting to Feet per Hour

  1. Understand the relationship between a statute mile and a nautical mile. A statute mile is what Americans commonly use to measure long distances over land. A statute mile is equal to 5,280 feet.[1] A nautical mile is usually used to measure distances that are across open water or space. A nautical mile is equal to 6,076 feet.
    • Knots are determined by how many nautical miles are being travelled per hour. 1 knot = 1 nautical mile per hour. [2]
  2. Multiply the knots by 6,076. This converts the rate in knots to feet per hour, since there are 6,076 feet in a nautical mile.
    • For example, if a boat is travelling at 17 knots, to find how many feet per hour, calculate <math>17 \times 6,076 = 103,292</math>.
  3. Divide the feet per hour rate by 5,280. Since there are 5,280 feet in a statute mile, to know how many miles per hour something is traveling, divide the number of feet per hour by 5,280.[3]
    • For example, if a boat is travelling 103,292 feet per hour, to find out how many miles per hour it is travelling, you would calculate <math>\frac{103,292}{5,280} = 19.56</math>
      So, a boat travelling at 17 knots is travelling about 19.56 miles per hour.

Multiplying by the Rate Conversion

  1. Understand the relationship between knots and miles per hour. Both are rates of speed. Something travelling at 1 knot is equal to travelling 1.152 miles per hour.[4]
  2. Set up the conversion formula. Since 1 knot = 1.152 miles per hour, the formula is <math>1.152x = y</math>, where <math>x</math> equals the rate in knots, and <math>y</math> equals the rate in miles per hour.[5]
  3. Plug the number of knots into the formula. Make sure you are substituting for the <math>x</math> value. Multiply to find the number of miles per hour.
    • For example, if the wind is blowing at 20 knots, you would calculate as follows:
      <math>1.152(20) = y</math>
      <math>23.04 = y</math>.
      So, if the wind blows at 20 knots, it is going about 23 miles per hour.

Converting Miles Per Hour to Knots

  1. Multiply the miles per hour by 5,280, then divide by 6,076. This converts the rate to feet per hour, since there are 5,280 feet in a statute mile. Dividing by 6,076, the number of feet in a nautical mile, tells you how many knots something is travelling.
    • For example, a boat might be travelling 20 mph.
    • Converting to feet per hour: <math>20 \times 5,280 = 105,600</math>.
    • Converting to knots: <math>\frac{105,600}{6,076} = 17.38</math>.
    • So, a boat travelling 20 mph is travelling at about 17 knots.
  2. Multiply the miles per hour by 0.869. This is the conversion rate, since there are about 0.869 knots per mile. The product will tell you the rate in knots.[6]
    • For example, the wind might be blowing at 25 miles per hour.
    • Simply multiply, or use the formula <math>0.869x = y</math>, where <math>x</math> equals the rate in miles per hour, and <math>y</math> equals the rate in knots.
    • <math>25(0.869) = 21.725</math>
    • So, wind blowing at 25 mph is blowing at about 22 knots.
  3. Try this sample problem. A red boat is travelling at 15 knots. A blue boat is travelling at 17 miles per hour. Which boat is travelling faster?
    • To convert how fast the blue boat is travelling in mph to knots, multiply by the number of miles per hour by 0.869:
      <math>0.869(17) = 14.77 \; \text{knots}</math>
    • The red boat is travelling at 15 knots; the blue boat is travelling a little less than 15 knots. So the red boat is travelling faster.

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Sources and Citations

  1. ↑ http://indianapublicmedia.org/amomentofscience/difference-mile-nautical-mile/
  2. ↑ https://www.grc.nasa.gov/www/k-12/WindTunnel/Activities/knots_vs_mph.html
  3. ↑ http://www.sciencemadesimple.com/feet-to-miles.html
  4. ↑ https://www.lpl.arizona.edu/~rhill/conversion/windspd.htm
  5. ↑ http://www.conversion-website.com/speed/knot-to-mile-per-hour.html
  6. ↑ http://www.conversion-website.com/speed/mile-per-hour-to-knot.html
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