Speed Converter
Convert between speed units including km/h, mph, m/s, ft/s, and knots. Free online speed conversion calculator.
What is Speed Converter?
A speed converter translates between different velocity units — km/h, mph, m/s, knots, and feet per second. Different fields use different speed units: road speed in km/h (most countries) or mph (US/UK), aviation and maritime in knots, science in m/s, and engineering sometimes in ft/s. This tool handles all common conversions for anyone working across these domains — drivers comparing speed limits internationally, pilots converting between knots and km/h, or engineers working with wind speed data.
How It Works
Enter a speed value with its source unit and select the target unit. The tool converts through meters per second (m/s) as the base unit using precise factors: 1 km/h = 0.27778 m/s, 1 mph = 0.44704 m/s, 1 knot = 0.51444 m/s. All conversions update simultaneously so you can see the speed expressed in every supported unit at once. Results use appropriate precision — whole numbers for road speeds, decimals for scientific applications.
Quick Reference
| km/h | mph | m/s | Knots |
|---|---|---|---|
| 1 | 0.621 | 0.278 | 0.540 |
| 50 | 31.07 | 13.89 | 26.99 |
| 100 | 62.14 | 27.78 | 53.99 |
| 120 | 74.56 | 33.33 | 64.79 |
| 200 | 124.27 | 55.56 | 107.99 |
Common Use Cases
- •Converting speed limits between km/h and mph when driving internationally or renting abroad
- •Translating wind speed measurements between knots, km/h, and mph for weather data
- •Converting running pace between min/km and min/mile for international fitness comparisons
- •Translating aviation speeds between knots, km/h, and mach number for flight planning
- •Converting scientific velocity measurements between m/s and other practical units
- •Translating manufacturing line speeds between m/min and ft/min for equipment specifications
Frequently Asked Questions
What is a knot?▼
A knot is one nautical mile per hour, equal to approximately 1.852 km/h or 1.151 mph.
How do I convert between km/h and m/s quickly?▼
Divide by 3.6 to go from km/h to m/s, and multiply by 3.6 for the reverse. The factor is 3,600 seconds per hour divided by 1,000 metres per kilometre. So 100 km/h is about 27.8 m/s.
What is a knot and why is it used?▼
A knot is one nautical mile per hour, or exactly 1.852 km/h. It persists in aviation and at sea because a nautical mile is one minute of latitude, which makes chart navigation arithmetic straightforward.
What is Mach number and is it a fixed speed?▼
Mach is the ratio of an object's speed to the local speed of sound, so it is not a fixed figure. Sound travels at roughly 1,225 km/h at sea level but only about 1,062 km/h in the thin, cold air at 11,000 metres. Mach 1 therefore corresponds to different ground speeds at different altitudes.
How do pace and speed relate for runners?▼
They are reciprocals. Pace is time per unit distance (minutes per kilometre or mile) while speed is distance per unit time. A 5:00 min/km pace is 12 km/h. A four-hour marathon is close to 5:41 min/km, or about 10.55 km/h.
What is the speed of light in these units?▼
Exactly 299,792,458 metres per second by definition — the metre is defined from it — which is about 1,079,252,849 km/h or roughly 671 million mph.
Further Reading
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