How To Convert Miles per Hour to Knots
Formula: knots = miles per hour × 0.8689762419
Example: 72 mph × 0.8689762419 = 62.5662894168 kn
To convert mph to knots by hand, multiply your mph value by 0.8689762419.
This works because a knot is based on a nautical mile per hour, and a nautical mile is longer than a standard mile.
If you want a quick estimate, you can round the factor to 0.869.
Quick Answer
1 mph = 0.8689762419 kn
- 10 mph = 8.689762419 kn
- 55 mph = 47.7936933045 kn
- 70 mph = 60.828336933 kn
Conversion Formula
kn = mph × 0.8689762419
This means you take the speed in miles per hour and multiply it by 0.8689762419 to get the same speed in knots.
The number 0.8689762419 comes from the fixed relationship between a mile and a nautical mile, where 1 nautical mile = 1.852 kilometers and 1 mile = 1.609344 kilometers.
- Write down the speed in mph.
- Multiply it by 0.8689762419.
- The result is the speed in knots (kn).
Mile per hour
A mile per hour is a unit of speed that tells how many miles are traveled in one hour. The symbol is mph.
It became common with road travel and car speed limits, especially in countries that use miles. It is still widely used for driving speeds and many weather reports.
- Car speedometers and road speed limits
- Running and cycling speeds (casual tracking)
- Wind speed in some forecasts
- Speed limits for boats on inland waterways in some regions
- General everyday speed comparisons
Knot
A knot is a unit of speed equal to one nautical mile per hour. The symbol is kn.
It has a long history in navigation, where sailors measured speed at sea using nautical methods, which is why it is tied to the nautical mile. Today it remains the standard speed unit for marine and aviation use.
- Boat and ship speeds at sea
- Aviation speed (airspeed and flight planning)
- Marine weather reports and sea forecasts
- Navigation charts and route timing on water
- Sailing and racing performance
Is this Conversion of Miles per Hour To Knots Accurate?
Yes. This conversion is based on the internationally defined mile and nautical mile. Since 1 mile is exactly 1.609344 kilometers and 1 nautical mile is exactly 1.852 kilometers, the ratio is fixed and gives 1 mph = 0.8689762419 kn.
Our converter uses this exact relationship, which is the same basis used in navigation, aviation references, and technical standards. For more details on how we choose and verify standard values, read our accuracy standards.
Real Life Examples
Here are practical mph speeds converted into knots, using the same exact factor (0.8689762419) every time.
- School zone driving: 20 mph = 17.379524838 kn, useful when a marine app shows speed in knots but you think in mph.
- City driving: 30 mph = 26.069287257 kn, helps compare a boat’s speed readout to familiar road speeds.
- Steady suburban road: 45 mph = 39.1039308855 kn, handy when planning a trip that mixes road and water travel timing.
- Highway cruising: 65 mph = 56.4834557235 kn, useful when translating speed limits into nautical terms for training or study.
- Typical small powerboat pace: 15 mph = 13.0346436285 kn, helps estimate arrival time when your GPS shows knots.
- Fast boat run: 50 mph = 43.448812095 kn, useful when comparing performance specs shown in different units.
- Strong wind report in mph: 40 mph = 34.759049676 kn, helpful for sailors who usually read wind in knots.
- Quick check for 72 mph: 72 mph = 62.5662894168 kn, useful when converting a specific speed from a chart or test question.
Quick Tips
- To go from mph to knots, multiply by 0.8689762419.
- For a fast mental estimate, use 0.869 (very close for everyday use).
- Knots will always be a bit smaller than mph for the same speed.
- To double check, 10 mph should be about 8.7 kn.
- If you need the reverse, knots to mph is about × 1.15078.