Speed Converter
Convert between km/h, mph, m/s, knots, and more speed units instantly.
What is a Speed Converter?
A speed converter is a tool that transforms velocity measurements from one unit to another. Speed measures how fast an object travels, expressed as distance divided by time.
Different units are used in different contexts: km/h and mph for road vehicles, m/s in physics, knots in aviation and maritime, and Mach numbers for supersonic speeds.
Understanding speed conversions is essential when traveling internationally (speed limits differ), following weather reports (wind speeds), or studying physics and engineering.
Speed Conversion Formulas
Common Conversions
- km/h to mph: mph = km/h × 0.621371
- mph to km/h: km/h = mph × 1.60934
- m/s to km/h: km/h = m/s × 3.6
- km/h to m/s: m/s = km/h ÷ 3.6
- knots to km/h: km/h = knots × 1.852
- knots to mph: mph = knots × 1.15078
Quick Reference Table
| From | To | Multiply by |
|---|---|---|
| 1 km/h | mph | 0.621 |
| 1 mph | km/h | 1.609 |
| 1 m/s | km/h | 3.6 |
| 1 m/s | mph | 2.237 |
| 1 knot | km/h | 1.852 |
| 1 knot | mph | 1.151 |
| Mach 1 | km/h | 1,234.8 |
| Speed of light | km/h | 1,079,252,849 |
Common Speed Conversions
km/h to mph
- 30 km/h = 18.6 mph (city driving)
- 50 km/h = 31.1 mph (urban limit)
- 80 km/h = 49.7 mph
- 100 km/h = 62.1 mph (highway)
- 120 km/h = 74.6 mph (autobahn)
- 200 km/h = 124.3 mph (sports car)
mph to km/h
- 25 mph = 40.2 km/h (school zone)
- 45 mph = 72.4 km/h
- 55 mph = 88.5 km/h
- 65 mph = 104.6 km/h (US highway)
- 75 mph = 120.7 km/h
- 100 mph = 160.9 km/h
Notable Speeds
- Walking: 5 km/h (3.1 mph)
- Running (jogging): 10 km/h (6.2 mph)
- Cycling: 20-30 km/h (12-19 mph)
- Usain Bolt (record): 44.72 km/h (27.8 mph)
- Cheetah (top speed): 120 km/h (75 mph)
- Commercial airplane: 900 km/h (560 mph)
- Sound (sea level): 1,234.8 km/h (767 mph) = Mach 1
Frequently Asked Questions
How do I convert km/h to mph?
To convert km/h to mph, multiply by 0.621371. For a quick estimate, multiply by 0.6 or divide by 1.6. For example, 100 km/h ≈ 60 mph (exact: 62.14 mph). This is useful when driving in countries with different speed limit systems.
What is a knot in speed measurement?
A knot is one nautical mile per hour. One knot equals 1.852 km/h or 1.151 mph. Knots are the standard unit for maritime and aviation speeds because they relate directly to navigation using latitude/longitude (1 nautical mile = 1 minute of latitude).
What is Mach speed?
Mach is the ratio of an object's speed to the speed of sound. Mach 1 equals the speed of sound (about 1,234.8 km/h or 767 mph at sea level). Mach 2 is twice the speed of sound. Fighter jets and the Concorde flew at supersonic (above Mach 1) speeds.
Why do scientists use m/s instead of km/h?
Meters per second (m/s) is the SI unit for speed, making calculations in physics simpler. It connects directly to other SI units like meters (distance) and seconds (time), and formulas like kinetic energy (½mv²) work cleanly with m/s.
What's the speed of light?
The speed of light in a vacuum is approximately 299,792,458 m/s or about 1.079 billion km/h. It's the cosmic speed limit - nothing can travel faster. Light from the Sun takes about 8 minutes to reach Earth.
Speed Conversion Tips
- Quick km/h to mph: Multiply by 0.6 or divide by 1.6 for estimates
- Quick mph to km/h: Multiply by 1.6
- m/s to km/h: Multiply by 3.6 (easy to remember!)
- Knots context: Used for ships, planes, and wind speed
- Mach varies: Speed of sound changes with altitude and temperature
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