MPH to Knots Converter

One mile per hour is 0.868976 knot, or about 0.87 knot. To convert mph to knots, multiply by 0.868976, or divide by 1.150779. For example, 10 mph is 8.69 knots, 25 mph is 21.724 knots and 55 mph is 47.794 knots.

Why 1 MPH Is 0.869 Knot

A mile per hour is one statute mile per hour, and a statute mile is 5,280 feet, exactly 1,609.344 meters. A knot is one nautical mile per hour, and the international nautical mile is exactly 1,852 meters. Divide one by the other: 1,609.344 ÷ 1,852 = 0.868976 knot per mph. The reverse factor, 1,852 ÷ 1,609.344, is 1.150779 mph per knot.

Both miles are fixed in meters, so the conversion is exact; the factors above are rounded to six decimal places. The converter above works both ways: type a speed in mph or in knots and the other box updates. The same speed in km/h and in meters per second is shown under the result.

MPH to Knots Conversion Chart

Every whole mph from 1 to 20:

MPH	Knots	km/h
1	0.869	1.609
2	1.738	3.219
3	2.607	4.828
4	3.476	6.437
5	4.345	8.047
6	5.214	9.656
7	6.083	11.265
8	6.952	12.875
9	7.821	14.484
10	8.69	16.093
11	9.559	17.703
12	10.428	19.312
13	11.297	20.921
14	12.166	22.531
15	13.035	24.14
16	13.904	25.75
17	14.773	27.359
18	15.642	28.968
19	16.511	30.578
20	17.38	32.187

From 25 to 500 mph:

MPH	Knots	km/h
25	21.724	40.234
30	26.069	48.28
35	30.414	56.327
40	34.759	64.374
45	39.104	72.42
50	43.449	80.467
55	47.794	88.514
60	52.139	96.561
65	56.483	104.607
70	60.828	112.654
75	65.173	120.701
80	69.518	128.748
85	73.863	136.794
90	78.208	144.841
95	82.553	152.888
100	86.898	160.934
150	130.346	241.402
200	173.795	321.869
300	260.693	482.803
450	391.039	724.205
500	434.488	804.672

Quick Ways to Convert MPH to Knots in Your Head

• Subtract 13 percent: 50 mph minus 6.5 is 43.5 knots; the exact answer is 43.449 knots.
• Multiply by 7, then divide by 8: 40 mph × 7 ÷ 8 = 35 knots; the exact answer is 34.759 knots.
• Knots back to mph: add 15 percent. 20 knots plus 3 is 23 mph; the exact answer is 23.016 mph.

Wind Warnings in MPH and Knots

The National Weather Service uses both units. It describes its tropical storm and hurricane warnings by sustained winds in mph, and its gale, storm and hurricane force wind warnings, for winds not directly associated with a tropical cyclone, by sustained winds or frequent gusts in knots. Each one in both units:

Warning	MPH	Knots
Tropical storm warning	39 to 73	33.9 to 63.4
Hurricane warning	74 or more	64.3 or more
Gale warning	39.1 to 54.1	34 to 47
Storm warning	55.2 to 72.5	48 to 63
Hurricane force wind warning	73.6 or more	64 or more

Small craft advisory thresholds depend on the area. In the NWS Eastern Region, which includes the coast from Maine to South Carolina, a small craft advisory covers sustained winds or frequent gusts of 25 to 33 knots, about 28.8 to 38 mph, with a lower starting point in some harbors and bays.

MPH or Knots on the Water

Nautical charts measure distance in nautical miles, so boat speeds, currents and marine winds are usually given in knots; NOAA’s Coast Pilot, for example, gives current and wind speeds in knots. Statute miles still appear on U.S. waters: the Coast Pilot gives distances along the Intracoastal Waterway in statute miles, and its Great Lakes volume uses statute miles too. Use the same kind of mile for speed and distance before you work out a passage time: mph with statute miles, or knots with nautical miles.

More Speed and Distance Converters

For the other direction, the Knots to MPH Converter turns knots into miles per hour. To convert distances, use the Miles to Nautical Miles Converter. The Speed, Distance and Time Calculator works out passage times in mph or knots, and the Boat Speed Calculator estimates a planing boat’s top speed from its horsepower and weight.

Frequently Asked Questions