To convert knots to mph, multiply by approximately 1.150779. To convert knots to km/h, multiply by exactly 1.852. For example, 20 knots is about 23.02 mph or exactly 37.04 km/h. The speed stays the same; only the unit changes.
A knot means one nautical mile per hour. That makes it different from a nautical mile, which measures distance alone. This reference brings the forward and reverse conversions together, including meters per second, so you can read a number in another unit without confusing speed with distance.
What is a knot?
The international nautical mile is exactly 1,852 meters. Traveling one nautical mile in one hour corresponds to a speed of one knot. NOAA explains the distinction between nautical miles and knots and their use in nautical measurement.
Write a speed as “15 knots,” not “15 knots per hour.” The hour is already included in the definition. In contrast, “15 nautical miles” describes a distance without saying how quickly it was covered. You may see knots abbreviated as kn, kt or kts in different displays; check the unit label rather than treating a bare number as mph.
The mile in mph is the ordinary statute mile, equal to exactly 1,609.344 meters in the international-foot system. It is shorter than a nautical mile. NIST’s unit conversion table gives that exact mile length. A speed therefore has a larger numerical value in mph than in knots.
Convert knots to mph and km/h
mph = knots × (1,852 ÷ 1,609.344)
km/h = knots × 1.852
The first factor is approximately 1.150779448. Using 1.150779 is convenient for ordinary calculator work; using the fraction keeps the definition exact until you round the answer. The second factor, 1.852, is exact because a kilometer contains 1,000 meters.
For an illustrative value of 12 knots, the calculations are 12 × (1,852 ÷ 1,609.344) = approximately 13.81 mph, and 12 × 1.852 = 22.224 km/h. Rounded to two decimal places, that is 13.81 mph and 22.22 km/h. These are two descriptions of the same given speed, not different measurements.
Knots conversion chart
This chart uses the exact length definitions, then rounds the results to two decimal places. The selected numbers are arithmetic examples, not recommended speeds or weather categories.
| Knots | MPH | KM/H | M/S |
|---|---|---|---|
| 1 | 1.15 | 1.85 | 0.51 |
| 5 | 5.75 | 9.26 | 2.57 |
| 10 | 11.51 | 18.52 | 5.14 |
| 15 | 17.26 | 27.78 | 7.72 |
| 20 | 23.02 | 37.04 | 10.29 |
| 25 | 28.77 | 46.30 | 12.86 |
| 30 | 34.52 | 55.56 | 15.43 |
| 40 | 46.03 | 74.08 | 20.58 |
| 50 | 57.54 | 92.60 | 25.72 |
| 60 | 69.05 | 111.12 | 30.87 |
Read across a row to compare units. For instance, the 30-knot row gives 34.52 mph and 55.56 km/h. If your value falls between the listed rows, calculate it with the formula rather than selecting the nearest row and treating it as exact.
Convert mph or km/h back to knots
knots = mph × (1,609.344 ÷ 1,852)
knots = km/h ÷ 1.852
For mph, the multiplier is approximately 0.868976242. For km/h, dividing by 1.852 is usually easier than remembering its reciprocal, approximately 0.539956803. Multiplying by the forward factor again will not reverse the conversion.
As a worked example, a given 25 mph becomes approximately 21.72 knots. A separate example of 40 km/h becomes approximately 21.60 knots. Those starting values are different speeds, even though their converted results are fairly close. Label every intermediate result to avoid swapping the two examples.
For an exact round-trip check, start with 10 knots. It becomes 18.52 km/h, and 18.52 ÷ 1.852 returns 10 knots. A rounded mph value may not return the starting number perfectly because some digits were discarded along the way.
Convert knots to meters per second
m/s = knots × (1,852 ÷ 3,600)
knots = m/s × (3,600 ÷ 1,852)
There are 3,600 seconds in an hour, so one knot is approximately 0.514444444 m/s. NIST lists the knot using the exact fraction 1,852/3,600 m/s. Conversely, one m/s is approximately 1.943844492 knots.
An illustrative 8 knots converts to approximately 4.12 m/s. Starting instead with 5 m/s gives approximately 9.72 knots. Keep the time unit in view: switching from hours to seconds is why this conversion cannot use the same multiplier as knots to km/h.
Rounding and common mistakes
Use the full factor during the calculation and round only the final answer. Two decimal places make the examples easy to compare, but do not make an original reading more precise. If a source reports a whole-number speed, displaying many decimal places afterward can suggest accuracy the source never supplied.
Multiplying knots by 1.15 gives a quick mph estimate. For example, 20 × 1.15 = 23 mph, compared with approximately 23.02 mph from the exact definitions. Use the exact fraction when preparing a table or checking another calculation. Never replace the knot-to-km/h factor with the familiar mph-to-km/h factor: they start with different units.
Converting a wind-speed value uses the same arithmetic, but does not establish what the conditions mean or whether an activity is safe. This is a unit reference, not navigation, route-planning, boat-operation or weather-safety guidance.
Keep related measurements separate
If your starting number is ordinary mph rather than knots, see the mph-to-km/h reference. For distances with no time component, use the miles-to-kilometers guide. Neither a mile nor a kilometer by itself is a speed.
A basic calculator is enough for these formulas. If you prefer a separate desktop tool, you can browse basic desktop calculators on Amazon. Enter the starting value, apply the factor for its actual unit, and add the destination unit to the answer.
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