Speed Converter
Convert between mph, km/h, m/s, knots and more instantly. Type any value to update all fields simultaneously.
How fast is 660 knots in mph and km/h?
660 knots is 759.5 mph or 1,222.3 km/h — just under the speed of sound, which at sea level in standard conditions is about 661 knots (761 mph). That's why 660 knots shows up so often in aviation trivia: it's roughly the line an aircraft crosses when it goes supersonic at low altitude.
To convert any speed in knots yourself: multiply by 1.15078 for mph, or by 1.852 for km/h (a knot is exactly one nautical mile — 1.852 km — per hour).
| Knots | mph | km/h |
|---|---|---|
| 140 knots | 161.1 mph | 259.3 km/h |
| 295 knots | 339.5 mph | 546.3 km/h |
| 660 knots | 759.5 mph | 1,222.3 km/h |
Going the other way: 295 km/h is 183.3 mph (a common top-speed figure for performance cars), and 660 mph is 1,062.2 km/h.
Ships and aircraft use knots because navigation charts are based on nautical miles, which map neatly onto degrees of latitude — one minute of latitude is one nautical mile.
Common speed conversions
| Speed | mph | km/h |
|---|---|---|
| 660 knots | 759.5 mph | 1,222.3 km/h |
| 295 km/h | 183.3 mph | 295 km/h |
| 140 knots | 161.1 mph | 259.3 km/h |
| 60 knots | 69.0 mph | 111.1 km/h |
Common Speed Conversions
How fast is 660 knots?
660 knots equals about 759.5 mph or 1,222.3 km/h. Knots measure nautical miles per hour; 1 knot = 1.15078 mph = 1.852 km/h, so 660 knots × 1.15078 ≈ 759.5 mph.
How many km/h in 1 mph?
1 mile per hour = 1.60934 kilometres per hour. To convert mph to km/h, multiply by 1.609. For a rough mental estimate, multiply by 1.6. So 60 mph ≈ 96.6 km/h, and 70 mph (UK motorway limit) ≈ 112.7 km/h.
What is a knot and how does it compare to mph?
A knot is 1 nautical mile per hour. 1 nautical mile = 1,852 metres (the length of 1 arc-minute of latitude). 1 knot ≈ 1.15078 mph or 1.852 km/h. Knots are used in aviation and maritime navigation because nautical miles directly relate to latitude, simplifying navigation calculations.
What is Mach 1 in mph?
Mach 1 (the speed of sound at sea level, 15°C) ≈ 340.29 m/s ≈ 761.2 mph ≈ 1,225 km/h. The speed of sound varies with altitude and temperature — at cruising altitude (~35,000 ft) it drops to about 295 m/s (660 mph), which is why aircraft Mach numbers matter more than absolute speeds at altitude.
Why does the UK still use mph for road speeds?
Despite the UK's official adoption of the metric system, road speed limits and speedometers remain in miles per hour under the Traffic Signs Regulations. This is retained largely due to cultural familiarity and the cost of changing road signage across the entire network. There is no current government plan to switch to km/h.