Knots to MPH Converter
Convert between knots (nautical miles per hour, kt) and statute miles per hour (mph) in both directions. Includes km/h for reference in the FAQ.
Last updated: September 2026
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About this calculator
A knot is one nautical mile per hour. The nautical mile is defined as exactly 1 852 metres, based historically on 1 minute of arc along a meridian of the Earth. 1 knot = 1.852 km/h = 1.15078 mph exactly (well, 1.150779 to more decimals). Knots are used in aviation and marine navigation because 1 knot equals 1 minute of latitude per hour — a huge convenience for chart work when your position is given in latitude/longitude.
Mph (statute miles per hour) is the US ground-transport speed unit. The statute mile (5 280 ft = 1 609.344 m) has no navigational significance — it is a Roman-mile-derived land measure. Km/h is the international road speed unit; 1 kt ≈ 1.852 km/h.
Aviation and marine speeds are always quoted in knots even in US airspace ("cleared to 250 knots below 10 000 ft" for Class B airspace). Cars, trains, and everyday US life quote mph. Wind speeds in weather reports vary — the Beaufort scale is originally in knots but consumer forecasts translate to mph.
How to use
Example — 100 knots to mph. 100 × 1.15078 = 115.08 mph. A Cessna 172 cruising at 100 KTAS (knots true airspeed) is going 115 mph over the ground in still air. Example — 65 mph to knots. 65 / 1.15078 = 56.5 kt. Highway speed in nautical units. Notice knots are always a smaller number than mph for the same speed (knots are the "bigger" unit because they cover more ground per hour by a 15% factor).
Frequently asked questions
Why do pilots use knots instead of mph?
The nautical mile equals one minute of latitude on any meridian, so a knot equals one minute of latitude per hour. Navigation charts are ruled in minutes of latitude, and speed-time-distance mental math becomes trivial. Also, all international aviation standards (ICAO) use knots — mph would be a US-only outlier and would break international interoperability.
Is a "knot per hour" a real unit?
No — a knot is already a unit of speed (nautical miles per hour). "Knots per hour" would be an acceleration (nm/hr²), which is essentially never useful. If you hear "knots per hour" it's usually a linguistic mistake for "knots" or an actual acceleration measurement in a niche engineering context.
What is 100 knots in km/h?
100 knots × 1.852 = 185.2 km/h. The conversion to km/h is exactly 1.852 by definition of the nautical mile. Kts to km/h is the cleanest conversion because both are metric-rooted; kts to mph is the messy one because the statute mile has no metric origin.
What is Mach in knots?
Mach is a ratio, not a fixed speed — it depends on temperature and thus altitude. Mach 1 at sea level (15°C) is about 661 kt (761 mph). At FL350 (~35 000 ft, −55°C) Mach 1 drops to about 573 kt (660 mph). Airliners typically cruise at Mach 0.78–0.85, roughly 450–490 kt true airspeed at that altitude.