Miles per Hour to Knots
Convert miles per hour (mph) to knots (kn). Both measure velocity, and the conversion comes up in driving, aviation, sports work.
The Formula
``
knots = miles per hour × 0.868976241901
miles per hour = knots × 1.15077944802
`
One miles per hour is 0.868976 knots, and one knot is 1.1508 miles per hour.
Conversion Table
| Miles per Hour | Knots |
|---|---|
| 1 mph | 0.868976 kn |
| 2 mph | 1.738 kn |
| 5 mph | 4.3449 kn |
| 10 mph | 8.6898 kn |
| 25 mph | 21.7244 kn |
| 50 mph | 43.4488 kn |
| 100 mph | 86.8976 kn |
| 500 mph | 434.4881 kn |
| 1,000 mph | 868.9762 kn |
The Other Direction
| Knots | Miles per Hour |
|---|---|
| 1 kn | 1.1508 mph |
| 2 kn | 2.3016 mph |
| 5 kn | 5.7539 mph |
| 10 kn | 11.5078 mph |
| 25 kn | 28.7695 mph |
| 50 kn | 57.539 mph |
| 100 kn | 115.0779 mph |
| 500 kn | 575.3897 mph |
| 1,000 kn | 1,150.78 mph |
What Each Unit Is
Miles per Hour (mph) — miles travelled per hour, equal to 1.609344 km/h exactly. The road-speed unit of the US and UK.
Knots (kn) — one nautical mile per hour, or exactly 1.852 km/h. From the knots in a line paid out behind a ship: sailors counted knots passing in a fixed time to read speed.
A Sense of Scale
Residential limits are 25–30 mph- US freeways are 65–75 mph
- A jog is 6 mph
- An airliner cruises at 450–500 knots
- A hurricane starts at 64 knots
Doing It in Your Head
Multiply by 6, then divide by 7. That is off by 1.36% — close enough to judge a
distance, a weight or a price, and not close enough to sign off on a drawing.
Exact Mental shortcut 8.6898 kn 8.5714 kn 86.8976 kn 85.7143 kn
Precision
The factor 0.868976241901 is rounded. For engineering work carry more digits than the table above, and round only at the end — rounding at each step compounds.
Watch Out For
- Never say "knots per hour" — the "per hour" is already in the unit.
In Code
`javascript
const milePerHourToKnot = (value) => value * 0.868976241901;
``
Where This Conversion Comes Up
- Driving
- Aviation
- Sports
- Shipping
- Weather
How Many Decimals Do You Need?
Rounding the factor costs accuracy, and how much depends on the factor. Converting 137 mph with the factor truncated at each decimal place:
| Decimals kept | Factor | 137 mph becomes | Error |
|---|---|---|---|
| 0 | 1 | 137 | 15.0779% |
| 1 | 0.9 | 123.3 | 3.5702% |
| 2 | 0.87 | 119.19 | 0.1178% |
| 3 | 0.869 | 119.053 | 0.0027% |
| 4 | 0.869 | 119.053 | 0.0027% |
The right number of significant figures is set by your input, not by the converter. If you measured miles per hour to three significant figures, the answer in knots is only good to three — writing more digits claims precision the measurement never had.