Speed Converter
Convert between miles per hour, kilometers per hour, meters per second, knots, feet per second, and Mach. Used for driving speeds, aviation, maritime navigation, and physics.
| Unit | Value |
|---|---|
| Meters per second (m/s) | 26.8224 |
| Kilometers per hour (km/h) | 96.559868 |
| Miles per hour (mph) | 60 |
| Knots (kn) | 52.139025 |
| Feet per second (ft/s) | 88 |
| Mach (sea level) | 0.078822 |
Speed Unit Conversion Formulas
Speed is distance divided by time. Like other physical quantities, speed conversions work by normalizing to a common base unit — in this case, meters per second (m/s), the SI standard. Every speed unit has a fixed ratio to m/s, enabling conversion between any pair of units.
Result = Input × (From factor in m/s / To factor in m/s)
Speed Unit Reference Table
| Unit | Value in m/s | Common use |
|---|---|---|
| 1 m/s | 1 | SI base unit, physics |
| 1 km/h | 0.27778 m/s | Road speeds in most countries |
| 1 mph | 0.44704 m/s | Road speeds in US, UK |
| 1 knot | 0.51444 m/s | Aviation, maritime navigation |
| 1 ft/s | 0.3048 m/s | US engineering, ballistics |
| Mach 1 (sea level) | 340.29 m/s | Supersonic flight reference |
Common Speed Conversions
The mph-to-km/h conversion is the most commonly needed, used when switching between US road speeds (mph) and metric road speeds (km/h). The relationship is:
1 mph = 1.60934 km/h
1 km/h = 0.62137 mph
| mph | km/h | m/s | Context |
|---|---|---|---|
| 25 | 40.2 | 11.2 | Urban speed limit (US) |
| 30 | 48.3 | 13.4 | Urban speed limit (UK) |
| 55 | 88.5 | 24.6 | US highway |
| 60 | 96.6 | 26.8 | Common highway comparison |
| 65 | 104.6 | 29.1 | US Interstate common limit |
| 70 | 112.7 | 31.3 | UK motorway limit |
| 100 | 160.9 | 44.7 | Highway reference speed |
| 767 | 1,234 | 343 | Speed of sound (approx.) |
mph vs. km/h: Country Guide
Road speed limits are displayed in mph in three countries: the United States, the United Kingdom, and Myanmar. The rest of the world uses km/h. When driving internationally or importing a vehicle, knowing how to convert between these two is essential for road safety.
A useful rough approximation: km/h × 0.6 ≈ mph. So 100 km/h ≈ 60 mph. The exact factor is 0.62137, so 100 km/h = 62.1 mph, but 60 mph is close enough for quick estimates.
Knots in Aviation and Maritime
Aircraft airspeed and maritime vessel speed are universally measured in knots (nautical miles per hour). This convention persists because nautical miles and knots align naturally with Earth's coordinate system: 1 nautical mile = 1 arc-minute of latitude. Flight plans, weather forecasts at sea, and ATC communications all use knots worldwide, regardless of whether the country uses metric or imperial on land.
Commercial aircraft cruise at approximately 470–560 knots (860–1,040 km/h or 540–650 mph). Wind speeds in aviation weather reports (METARs) are also given in knots.
Frequently Asked Questions
How do I convert mph to km/h?
Multiply miles per hour by 1.60934 to get km/h. Example: 60 mph = 60 × 1.60934 = 96.56 km/h. To go the other way, multiply km/h by 0.62137.
What is a knot and how does it compare to mph?
A knot is one nautical mile per hour. 1 knot = 1.15078 mph = 1.852 km/h = 0.51444 m/s. Knots are used in aviation and maritime navigation because nautical miles align with Earth's latitude grid, making navigation calculations cleaner.
What is Mach 1 in km/h and mph?
Mach 1 (the speed of sound at sea level, 15°C) is approximately 340.29 m/s = 1,234.8 km/h = 767.3 mph. The speed of sound varies with air temperature and altitude, decreasing at higher altitudes.
How do I convert km/h to m/s?
Divide km/h by 3.6 (or multiply by 1/3.6 = 0.27778). Example: 90 km/h = 90 / 3.6 = 25 m/s. To go the other way: multiply m/s by 3.6. The factor 3.6 comes from 1 km = 1000 m and 1 hour = 3600 s: 1 km/h = 1000/3600 m/s = 1/3.6 m/s.
What is the speed of light and how fast is it?
The speed of light in a vacuum is exactly 299,792,458 m/s ≈ 299,792 km/s ≈ 186,282 miles per second ≈ 670,616,629 mph. This is approximately Mach 880,991 at sea level. Light can circle Earth about 7.5 times per second.
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