What is Speed Converter?
Speed Converter converts between six speed units simultaneously — km/h, mph, m/s, ft/s, knots, and Mach number. Enter a value in any unit and all others update instantly, so you can compare speeds across different measurement systems without doing multi-step conversions.
Mach values are calculated at sea level standard conditions (15°C, 1 atm). At cruising altitude, where temperatures are around −57°C, Mach 1 is approximately 1,062 km/h — lower than at sea level.
Supported Speed Units
Road Speeds
km/h and mph — the standard for vehicles, running, cycling, and weather wind speed.
Marine & Air
Knots (nautical mph) for ships and aircraft navigation. 1 knot = 1.852 km/h.
Scientific
m/s and ft/s for physics, engineering, and scientific calculations where SI units are standard.
How to Use Speed Converter
Enter speed
Type a speed value into any field — km/h, mph, m/s, ft/s, knots, or Mach.
See all units
All other unit fields update immediately. Compare the same speed across all systems at once.
Copy result
Click the copy icon next to the unit you need.
Speed Reference Points
| Speed | km/h | mph | Mach |
|---|---|---|---|
| City speed limit | 50 | 31 | 0.041 |
| Highway speed | 120 | 75 | 0.098 |
| Commercial aircraft | 900 | 560 | 0.85 |
| Speed of sound | 1,235 | 767 | 1.0 |
| SR-71 Blackbird | 3,540 | 2,200 | 3.3 |
Tips & Common Mistakes
Wind speed in weather forecasts is usually given in km/h or mph, but meteorology and aviation use knots. The converter makes switching between the two instant.
m/s is the SI standard. In physics and engineering problems, speeds in km/h must be divided by 3.6 to get m/s. The converter does this automatically.
Related Tools
- Length Converter — convert distances
- Weight Converter — convert mass units
- Time Duration Calculator — calculate elapsed time