Unit Conversion
Speed Converter
Easily convert speed units like kilometers per hour (km/h), meters per second (m/s), miles per hour (mph), and knots with our free online Speed Converter. Perfect for physics, travel, and vehicle speed comparisons.
How Does Speed Conversion Work?
Speed is distance traveled per unit of time. The SI unit is meters per second (m/s), but everyday life uses km/h (most countries), mph (US, UK), and knots (aviation, maritime). Converting between them requires a single multiplication factor since speed is a linear measurement — unlike area or volume conversions.
This converter supports 9 speed units across metric (m/s, km/h, km/s), imperial (mph, ft/s, in/s), nautical (knots), and physics scales (Mach, speed of light). All conversions use m/s as the base unit. A quick rule of thumb: km/h ÷ 1.609 = mph, or mph × 1.609 = km/h.
How to Use This Converter
- Enter a speed value and select the source unit
- Select the target unit you want to convert to
- Click Convert to see the result
- Use Swap to reverse the conversion direction
Common Use Cases
- Travel & road speed limits
- Aviation & flight planning
- Maritime navigation
- Physics & engineering
- Sports & athletics
- Weather & wind speed
Quick Reference — Common Speed Conversions
| From | To | Multiply By | Example |
|---|---|---|---|
| 1 km/h | mph | 0.6214 | 100 km/h = 62.14 mph |
| 1 mph | km/h | 1.6093 | 60 mph = 96.56 km/h |
| 1 m/s | km/h | 3.6 | 10 m/s = 36 km/h |
| 1 km/h | m/s | 0.2778 | 90 km/h = 25 m/s |
| 1 knot | km/h | 1.852 | 20 kn = 37.04 km/h |
| 1 knot | mph | 1.1508 | 100 kn = 115.08 mph |
| 1 m/s | ft/s | 3.2808 | 5 m/s = 16.4 ft/s |
| 1 mph | ft/s | 1.4667 | 60 mph = 88 ft/s |
| Mach 1 | km/h | 1,235 | Mach 2 = 2,470 km/h |
| Speed of light | km/s | 299,792 | 1c = 299,792 km/s |
Understanding Speed Units
Everyday & Metric Units
| m/s | SI standard — physics, science, engineering |
| km/h | Road speed in most countries worldwide |
| km/s | Orbital mechanics, spacecraft, astronomy |
| mph | Road speed in US, UK, and a few other countries |
| ft/s | Ballistics, US engineering, fluid dynamics |
Specialized Units
| Knots | Aviation & maritime — 1 kn = 1 nautical mile/hr |
| Mach | Speed relative to sound (~343 m/s at sea level, 20°C) |
| c | Speed of light in vacuum — 299,792,458 m/s exactly |
| in/s | Manufacturing, conveyor belts, precision machinery |
Real-World Speed Comparisons
| Object / Scenario | Speed | Equivalent |
|---|---|---|
| Walking (average) | 5 km/h | 3.1 mph / 1.4 m/s |
| Cycling (casual) | 15 km/h | 9.3 mph / 4.2 m/s |
| Usain Bolt (peak sprint) | 44.7 km/h | 27.8 mph / 12.4 m/s |
| City speed limit | 50 km/h | 31 mph / 13.9 m/s |
| Highway driving | 120 km/h | 74.6 mph / 33.3 m/s |
| Commercial aircraft (cruise) | 900 km/h | 560 mph / 486 kn / Mach 0.85 |
| Speed of sound (sea level) | 1,235 km/h | 767 mph / Mach 1 |
| SR-71 Blackbird (fastest jet) | 3,540 km/h | 2,200 mph / Mach 3.3 |
| ISS orbital speed | 27,600 km/h | 17,150 mph / 7.66 km/s |
| Speed of light | 1,079,252,849 km/h | 670,616,629 mph / 1c |
FAQ – Speed Converter
What is a speed converter?
A speed converter is a tool that converts measurements between different units of speed, such as km/h to mph, m/s to knots, or Mach to km/h. It's essential for travel, physics, aviation, maritime navigation, and any field that deals with velocity measurements across different unit systems.
How do I convert km/h to mph?
Divide km/h by 1.609 (or multiply by 0.6214). For example, 100 km/h = 62.14 mph. To convert mph to km/h, multiply by 1.609. A quick mental shortcut: km/h × 0.6 gives a rough mph estimate (100 km/h ≈ 60 mph). The exact factor is 1.60934.
What is a knot and why is it used in aviation?
A knot equals 1 nautical mile per hour (1.852 km/h or 1.151 mph). It's used in aviation and maritime because nautical miles are based on Earth's geometry — 1 nautical mile = 1 minute of latitude. This makes navigation calculations simpler when working with charts and coordinates. All international air traffic control uses knots.
What is Mach number?
Mach number is speed relative to the speed of sound. Mach 1 = the speed of sound, which is approximately 343 m/s (1,235 km/h / 767 mph) at sea level and 20°C. The speed of sound varies with temperature and altitude — at cruising altitude (35,000 ft), it's about 295 m/s. Subsonic is below Mach 1, supersonic is Mach 1–5, and hypersonic is above Mach 5.
Why do different countries use different speed units?
Most countries adopted the metric system (km/h) in the 19th–20th centuries. The US, UK (partially), and a few other countries retained miles per hour from the Imperial system. The UK uses mph on roads but km/h in some scientific contexts. Liberia and Myanmar are the only other countries that officially use mph. International aviation and shipping use knots worldwide regardless of country.
How fast is the speed of light?
The speed of light in a vacuum is exactly 299,792,458 m/s (about 1.08 billion km/h or 670 million mph). It's the universal speed limit — nothing with mass can reach it. Light travels from the Sun to Earth in about 8 minutes and 20 seconds, and from the Moon to Earth in about 1.3 seconds.
What is the difference between speed and velocity?
Speed is a scalar quantity — it only has magnitude (e.g., 60 km/h). Velocity is a vector — it has both magnitude and direction (e.g., 60 km/h north). A car driving in a circle at constant speed has changing velocity because its direction changes. This converter works with speed (magnitude only), which is what most practical applications need.
How do I convert m/s to km/h?
Multiply m/s by 3.6 to get km/h. For example, 10 m/s = 36 km/h. To convert km/h to m/s, divide by 3.6. The factor 3.6 comes from: 1 km = 1,000 m and 1 hour = 3,600 seconds, so 1 m/s = 3,600/1,000 = 3.6 km/h. This is one of the most common conversions in physics.
What speed unit is used for wind speed?
It depends on the context. Meteorologists use km/h or m/s in most countries, mph in the US, and knots in aviation weather reports (METARs/TAFs) worldwide. The Beaufort scale describes wind force from 0 (calm, <1 km/h) to 12 (hurricane, >118 km/h). Tornado intensity uses the Enhanced Fujita (EF) scale based on estimated wind speeds in mph.
Does the speed of sound change with conditions?
Yes. The speed of sound depends primarily on temperature and the medium. In air at 20°C, it's about 343 m/s (Mach 1). At 0°C, it drops to 331 m/s. At cruising altitude (−57°C), it's about 295 m/s. Sound travels faster in water (~1,480 m/s) and even faster in steel (~5,960 m/s). The Mach number in this converter uses the standard sea-level value of 343 m/s.