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Speed converter
How fast, in every unit people actually use. 6 units, converted from one table of exact factors.
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Worth knowing. Mach is not a fixed speed. The speed of sound drops as air gets colder, so mach 1 at altitude is slower than mach 1 at sea level.
1 mile/hour in every other speed unit
Computed by the same engine that runs the converter above, so these can never drift apart from it.
| From | Equals | Unit |
|---|---|---|
| 1 mile/hour | 0.44704 | meter/second (m/s) |
| 1 mile/hour | 1.609344 | kilometer/hour (km/h) |
| 1 mile/hour | 1.4666667 | foot/second (ft/s) |
| 1 mile/hour | 0.86897624 | knot (kn) |
| 1 mile/hour | 0.001313703 | mach (Mach) |
What each unit actually is
Most converters give you a number and stop. Where a figure is exact by definition we say so, and where it is an average or shifts with conditions we say that too — that is usually the thing you needed to know.
| Unit | Symbol | What it actually is |
|---|---|---|
| meter/second | m/s | The SI derived unit. |
| kilometer/hour | km/h | Exactly 1/3.6 m/s. |
| mile/hour | mph | Exact, since both the mile and the hour are defined. |
| foot/second | ft/s | Exact. |
| knot | kn | One nautical mile per hour. Exact. |
| mach | Mach | NOT a fixed unit. The speed of sound changes with temperature and altitude; 340.29 m/s is the value at sea level at 15 °C, and it is roughly 295 m/s at cruising altitude. |