Speed Converter | mph, km/h, m/s
Convert between mph, km/h, m/s, knots, and feet per second.
Quick presets:
RELATIVE SPEED (log scale)
What Is the Speed Converter | mph, km/h, m/s?
The Speed Converter instantly converts between 10 speed units: m/s (SI), km/h, km/s, cm/s, mph (US/UK road), ft/s, knots (nautical/aviation), Mach (sea level and high altitude), and percentage of light speed. A logarithmic speed bar gives instant visual context, from walking pace to the speed of light.
- ›Meters per second (m/s) is the SI base unit for speed
- ›Knots = nautical miles per hour; 1 nm = 1852 m (1 arcminute of latitude)
- ›Mach number depends on temperature and altitude, Mach 1 ≈ 340 m/s at sea level (20°C)
- ›Speed of light c = 299,792,458 m/s (exact, by SI definition)
- ›Click any result to copy it to the clipboard
Formula
Speed Conversion Factors (relative to 1 m/s)
1 m/s
3.6 km/h = 2.237 mph = 1.944 kn
1 km/h
0.2778 m/s = 0.6214 mph = 0.5400 kn
1 mph
1.6093 km/h = 0.4470 m/s = 0.8690 kn
1 knot
1.852 km/h = 0.5144 m/s = 1.1508 mph
Mach 1
≈ 340 m/s = 1224 km/h = 661 kn (sea level)
Speed of light
299,792,458 m/s = 1.079×10⁹ km/h
How to Use
- 1Enter a numeric speed value in the input field
- 2Select the source unit from the dropdown (m/s, km/h, mph, knots, etc.)
- 3Click Convert, all 10 equivalent speeds appear instantly
- 4Click any result row to copy that value to your clipboard
- 5Use the Quick Presets to load famous reference speeds (walking, sound, light)
- 6The logarithmic Speed Bar shows where your speed sits on a universal scale
Example Calculation
Highway speed: 60 mph
60 mph × 0.44704 = 26.82 m/s
60 mph × 0.86898 = 52.14 knots
60 mph × 1.46667 = 88.00 ft/s
60 mph / 767.3 = Mach 0.0782
Speed of sound at sea level: 340 m/s
340 m/s × 2.2369 = 760.5 mph
340 m/s × 1.9438 = 661.1 knots
340 m/s / 299,792,458 = 0.000001133c
Why do pilots use knots?
Nautical miles map directly onto degrees of latitude (1 nm = 1 arcminute), making navigation charts and position calculations straightforward. Knots have been the international standard for aviation and maritime navigation since the 1970s ICAO convention, unifying global air traffic control.
Understanding Speed Converter | mph, km/h, m/s
Speed Unit Reference Table
| Speed | m/s | km/h | mph | knots |
|---|---|---|---|---|
| Walking pace | 1.4 | 5.0 | 3.1 | 2.7 |
| Cycling (leisure) | 4.2 | 15 | 9.3 | 8.1 |
| City car (50 km/h) | 13.9 | 50 | 31.1 | 27.0 |
| Motorway (100 km/h) | 27.8 | 100 | 62.1 | 54.0 |
| High-speed train | 83.3 | 300 | 186.4 | 162.0 |
| Concorde | 604 | 2,180 | 1,354 | 1,176 |
| Speed of sound | 340 | 1,224 | 760.9 | 661.5 |
| LEO orbit | 7,800 | 28,080 | 17,450 | 15,160 |
| Speed of light | 299,792,458 | 1.08×10⁹ | 6.71×10⁸ | 5.83×10⁸ |
Frequently Asked Questions
What is a knot and why is it used in aviation?
Navigation at sea and in the air uses charts based on latitude and longitude. Since 1 nautical mile = 1 arcminute of latitude, distances on charts map directly to nautical miles without any conversion.
- ›1 knot = 1 nautical mile/hour = 1.852 km/h = 1.1508 mph
- ›1 nautical mile = 1852 m ≈ 6076 feet
- ›ICAO requires altitude in feet and speed in knots for international aviation
- ›Cruise speed of a commercial jet: about 450–490 knots (840–910 km/h)
What is Mach number and why does it change with altitude?
Sound speed in air depends on temperature: c = 331 × √(T/273) m/s. At −56°C (typical cruising altitude), c ≈ 295 m/s. The same aircraft speed represents a higher Mach number at altitude.
- ›Subsonic: Mach < 0.8 | Transonic: Mach 0.8–1.2 | Supersonic: Mach 1.2–5
- ›Hypersonic: Mach > 5, shock heating becomes severe
- ›Commercial jets cruise at Mach 0.78–0.85 (just below transonic)
- ›Concorde: Mach 2.0 | SR-71 Blackbird: Mach 3.3
How do I convert mph to km/h mentally?
The exact factor is 1.60934 km per mile. For quick mental maths, 1.6 is close enough for everyday use.
- ›30 mph = 48.3 km/h (urban limit in UK → 50 km/h zones in Europe)
- ›60 mph = 96.6 km/h (typical rural limit)
- ›70 mph = 112.7 km/h (UK motorway limit)
- ›100 km/h = 62.1 mph | 130 km/h = 80.8 mph (Autobahn limit)
What are the fastest speeds ever recorded?
- ›Parker Solar Probe (2024): ~192 km/s = 0.000064c, fastest human-made object
- ›SR-71 Blackbird (1976): 3,529 km/h = Mach 3.3, fastest manned aircraft
- ›ThrustSSC (1997): 1,228 km/h = Mach 1.02, first supersonic land vehicle
- ›Usain Bolt (2009): 44.72 km/h = 12.42 m/s, fastest human sprint
- ›Peregrine falcon dive: ~390 km/h, fastest animal
What is cm/s used for?
- ›Deep ocean thermohaline circulation: 1–10 cm/s
- ›Blood flow in capillaries: ~0.05 cm/s
- ›Typical glacier movement: 25–200 cm/day ≈ 0.0003–0.002 cm/s
- ›CGS unit system uses cm/s as the base speed unit
How fast is light and what can approach it?
The speed of light in vacuum is a universal constant, exact by SI definition since 1983. Special relativity forbids massive objects from reaching c, kinetic energy diverges to infinity as v → c.
- ›c = 299,792,458 m/s exactly (defines the metre)
- ›Light travels Earth circumference (40,075 km) in 0.134 seconds
- ›Light-minute = 17,987,547 km; light-year ≈ 9.461 × 10¹² km
- ›LHC protons: 99.9999991% c, Lorentz factor γ ≈ 7,500
Is this speed converter free to use?
Yes, completely free with no registration or account required. All conversions are performed locally in your browser, no data is sent to any server.