A speed converter instantly converts between miles per hour, kilometers per hour, knots, meters per second, feet per second, and Mach. Type any value and see all units update simultaneously.
Speed Converter
Speed Reference
| Reference | mph | km/h | knots | m/s |
|---|---|---|---|---|
| Walking pace | 3.1 | 5.0 | 2.7 | 1.4 |
| Cycling (casual) | 15 | 24.1 | 13.0 | 6.7 |
| US highway speed | 65 | 104.6 | 56.5 | 29.1 |
| 100 km/h (EU highway) | 62.1 | 100 | 54.0 | 27.8 |
| Commercial aircraft (cruise) | 500 | 804.7 | 434.5 | 223.5 |
| Speed of sound (Mach 1, sea level) | 767 | 1,235 | 666 | 340.3 |
How to Convert Speed Units
Speed unit conversion is common in travel, aviation, meteorology, and sports. The most common conversion is between mph (used in the US and UK) and km/h (used almost everywhere else). Understanding the relationship between speed units makes it easy to interpret speed limits, wind speeds, and vehicle specifications worldwide.
Step 1: Key Conversion Factors to Remember
1 mph = 1.60934 km/h. For quick mental math, multiply mph by 1.6. Going the other way: 1 km/h = 0.62137 mph, so multiply km/h by 0.6 for a rough estimate. 1 knot = 1.852 km/h = 1.15078 mph. The speed of sound at sea level (standard conditions) is approximately 340 m/s = 767 mph = 1,235 km/h = 1 Mach.
Step 2: Understanding Knots
Knots are used by sailors, aviators, and meteorologists. One knot equals one nautical mile per hour. A nautical mile (1.852 km) is based on the circumference of the Earth — 1 nautical mile equals 1 arc-minute of latitude. This makes navigation calculations simpler at sea. When you see wind speeds in weather forecasts, they are often in knots.
Step 3: Using Mach Numbers
Mach numbers are ratios of an object's speed to the local speed of sound. Mach 0.85 means 85% of the speed of sound — typical cruise speed for commercial jets. Supersonic is above Mach 1, hypersonic above Mach 5. The speed of sound changes with altitude and temperature, so Mach values are context-specific. At 35,000 ft, Mach 1 ≈ 295 m/s, not 340 m/s at sea level.
Frequently Asked Questions
How do I convert mph to km/h?
Multiply miles per hour by 1.60934 to get km/h. Example: 60 mph × 1.60934 = 96.56 km/h. For a quick mental estimate, multiply mph by 1.6. The exact conversion factor is 1 mile = 1.609344 kilometers.
What is a knot in speed?
A knot (kt or kn) is one nautical mile per hour. One nautical mile equals 1.852 kilometers or about 1.151 statute miles. Knots are used in maritime and aviation navigation. 1 knot = 1.852 km/h = 1.15078 mph.
What is Mach 1 in mph?
Mach 1 (the speed of sound at sea level, 0°C/32°F) is approximately 340.3 m/s, 767 mph, or 1,235 km/h. The speed of sound varies with altitude and temperature — higher altitude and colder air results in a slower speed of sound. At cruising altitude (35,000 ft), Mach 1 ≈ 295 m/s or 661 mph.
How fast is a knot compared to mph?
1 knot is approximately 1.15 mph or 1.852 km/h. So 100 knots ≈ 115 mph ≈ 185 km/h. A commercial aircraft cruises at roughly 450-500 knots (518-575 mph). A cargo ship might cruise at 14-20 knots (16-23 mph).
Is this speed converter free?
Yes, completely free with no signup required. All conversions run instantly in your browser.