Written by Muneeb Rana · Last updated 26 October 2026
Quick answer: To convert knots to mph, multiply by 1.15078. One knot is one nautical mile per hour, and a nautical mile is exactly 1,852 metres, so 1 knot also equals exactly 1.852 km/h. A boat at 20 knots is doing about 23 mph, and an airliner cruising at 480 knots is near 552 mph.
TL;DR
- mph = knots × 1.15078.
- km/h = knots × 1.852 (exact).
- Used at sea, in aviation and for wind.
- Speedometer PRO shows MPH or KM/H, not knots.
- Table below.
Knots to MPH formula
A nautical mile was originally tied to one minute of latitude and is now defined as exactly 1,852 m. Dividing 1,852 by 1,609.344 gives 1.15078, the mph factor. For km/h, multiply knots by 1.852.
Why knots
Because a nautical mile approximates one minute of arc on Earth's surface, navigators can relate distance directly to latitude on a chart. Ships, aircraft and weather services, including marine forecasts, still give speed and wind in knots.
Conversion table
| knots | mph | km/h |
|---|---|---|
| 1 | 1.2 | 1.9 |
| 5 | 5.8 | 9.3 |
| 10 | 11.5 | 18.5 |
| 15 | 17.3 | 27.8 |
| 20 | 23.0 | 37.0 |
| 25 | 28.8 | 46.3 |
| 30 | 34.5 | 55.6 |
| 40 | 46.0 | 74.1 |
| 50 | 57.5 | 92.6 |
| 100 | 115.1 | 185.2 |
| 250 | 287.7 | 463.0 |
| 480 | 552.4 | 889.0 |
Using a phone on a boat
Phone GPS works well on open water with a clear sky. Speedometer PRO shows MPH or KM/H, so divide mph by 1.15 for knots, or see the boat speedometer page. Keep the phone in a waterproof case and never rely on it as your only navigation aid.
Wind speeds in knots
Marine and aviation forecasts usually give wind in knots. A 10-knot breeze is about 11.5 mph; 20 knots about 23 mph; 34 knots, the threshold for a gale on the Beaufort scale, is about 39 mph. Converting wind to the unit you think in helps judge conditions before going out on the water.
Related converters
km/h to mph, mph to m/s, knots explained.
Related: Free speed tools · MPH guide: speed units explained · What is a knot in speed? · Boat speedometer app: GPS speed over ground · KMH to MPH converter · MPH to meters per second converter · Speedometer MPH and KM/H units · MPH to KMH converter
Get Speedometer PRO on Google Play · Download on the App Store · Set it up before you move; never handle your phone while driving.
Sources
- Knot (unit) (Wikipedia): en.wikipedia.org (accessed 26 October 2026)
- Unit conversion (NIST Office of Weights and Measures): nist.gov (accessed 26 October 2026)
FAQ
How many mph is one knot?
1.15078 mph. It comes from dividing a nautical mile of 1,852 m by a statute mile of 1,609.344 m.
How many km/h is one knot?
Exactly 1.852 km/h, because a nautical mile is defined as exactly 1,852 metres.
Is 30 knots fast for a boat?
30 knots is about 34.5 mph. That is quick for most leisure boats but routine for many powerboats and fast ferries.
Does Speedometer PRO show knots?
No. The current version shows MPH and KM/H only, so use this converter for knots.
Why do planes use knots?
Aviation shares navigation conventions with shipping, and nautical miles relate neatly to latitude on charts. Airspeed and wind are reported in knots worldwide.