Definition
A unit of speed equal to one nautical mile travelled in one hour. One nautical mile per hour is identical to one knot. A nautical mile is 6,076 feet, slightly longer than a statute mile (5,280 feet), so a speed expressed in NMPH is a higher actual distance per hour than the same number expressed in MPH.
Plain English
How many nautical miles you cover in an hour. One NMPH is the same thing as one knot.
Context Anchor
Seen when comparing aircraft speeds in knots with regular miles per hour during performance, navigation, or handbook calculations.
Derivation
‘Nautical’ comes from the Latin nauticus, meaning ‘of ships.’ The nautical mile was originally defined as one minute of latitude on the Earth’s surface, which made it natural for sea and air navigation. ‘Per hour’ simply means ‘in each hour.’ So NMPH literally means ‘sea-miles travelled in each hour’ — a sailing-era unit that aviation kept because charts and navigation are based on the same Earth geometry.
Why Pilots Care
Allows direct comparison of indicated airspeed in knots with ground references measured in statute miles.
Intuition Check
Do not read NMPH as regular miles per hour. NMPH means nautical miles per hour, and 100 NMPH is about 115 regular miles per hour.
Example Sentence 1
The handbook lists cruise speed as 110 knots, which is 110 NMPH, or about 127 MPH.
Example Sentence 2
Converting the wind speed from NMPH gave the correct groundspeed adjustment.