Speed Converter

Convert between different speed units quickly and accurately.

Result

62.14

mph

Common Speed Conversions

100 km/h = 62.14 mph

1 m/s = 3.6 km/h

1 knot = 1.852 km/h

1 mph = 1.609 km/h

Frequently Asked Questions

How do I convert km/h to mph?

To convert kilometers per hour to miles per hour, multiply by 0.621371. For example, 100 km/h = 100 × 0.621371 = 62.14 mph.

What is the speed of sound in km/h?

The speed of sound at sea level is approximately 1235 km/h (767 mph). This varies with temperature and altitude.

How fast is a knot compared to km/h?

One knot equals 1.852 kilometers per hour. Knots are commonly used in maritime and aviation contexts.

Overview

Speed is distance over time, and switching between its many units is a constant chore for drivers, pilots, sailors, runners, and engineers. The speed-converter on this page handles the units that show up in those contexts: meters per second (m/s), kilometers per hour (km/h), miles per hour (mph), feet per second (ft/s), knots (kn), and Mach number.

The SI base unit is meters per second, used in physics and engineering. In everyday use, road speeds are quoted in km/h in most of the world and in mph in the US and UK. The conversion between the two is a fixed 1.60934: 60 mph is 96.561 km/h, and 100 km/h is 62.137 mph. Feet per second appears in US engineering, ballistics, and some sports (a 90 mph fastball is 132 ft/s), while knots are used in aviation and marine navigation, defined as one nautical mile per hour, or 1.852 km/h exactly.

Mach number is a ratio, not an absolute speed: it is the local flow speed divided by the local speed of sound in air. Because the speed of sound depends on temperature (about 340.29 m/s at 15 °C sea level), Mach 1 is not a fixed number of km/h, though it is often quoted as roughly 1,235 km/h or 767 mph at standard sea-level conditions. Commercial jets cruise around Mach 0.78 to 0.85, and the Concorde cruised at Mach 2.04. For a quick conversion at sea level, multiplying Mach by 340 m/s gives an approximate m/s, then convert to km/h or mph from there.

For practical use, type a value in any field and the other units update at the same precision. A marathon pace of 3:00:00 (three hours over 42.195 km) is 14.07 km/h or 8.74 mph, which is roughly 3.91 m/s. A Boeing 737 at cruise of Mach 0.78 is about 265.7 m/s, 956.6 km/h, or 594.4 mph. The form shows the result across road, marine, aviation, and physics units in one step.

A handy reference: 1 m/s = 3.6 km/h = 2.23694 mph = 1.94384 kn = 3.28084 ft/s. 1 mph = 1.60934 km/h = 0.868976 kn. 1 kn = 1.852 km/h = 1.15078 mph. For runners, pace and speed are reciprocals: a pace of 5:00 min/km is 12 km/h, a pace of 4:00 min/km is 15 km/h, and a pace of 6:00 min/km is 10 km/h.

How to use

  1. Type a speed in any field: m/s, km/h, mph, ft/s, knots, or Mach.
  2. Read the matching values in the other units, updated automatically to the same precision.
  3. Use km/h or mph for road speeds, knots for marine and aviation, m/s for physics, and Mach for high-speed flight.
  4. For runners, pair this with the pace calculator to switch between pace (min/km or min/mi) and speed (km/h or mph).

Formula

1 m/s = 3.6 km/h = 2.23694 mph = 1.94384 kn = 3.28084 ft/s. 1 mph = 1.60934 km/h. 1 kn = 1.852 km/h = 1.15078 mph. Mach 1 ≈ 340.29 m/s at 15 °C sea level (depends on air temperature). Pace (min/km) = 60 / speed (km/h).

Interpreting your results

Negative values are valid in physics for direction but not meaningful as 'speed.' The form treats speed as a magnitude. For Mach, the local speed of sound depends on air temperature, so values are most useful at standard sea-level conditions (15 °C / 288.15 K). For knots, remember the unit is nautical miles per hour, not statute miles: a 10-knot boat covers 10 nmi in an hour, which is 11.508 statute miles or 18.52 km.

Frequently asked questions

What is a knot?
A knot is one nautical mile per hour. A nautical mile is 1,852 meters, so 1 knot equals 1.852 km/h or about 1.151 mph. Knots are used in marine and aviation navigation because one nautical mile equals one minute of latitude, which makes chart work straightforward.
How do I convert mph to km/h?
Multiply mph by 1.60934 to get km/h. The US highway speed limit of 65 mph, for example, is 65 × 1.60934 = 104.607 km/h. To go the other way, divide km/h by 1.60934, so 100 km/h is 62.137 mph.
Is Mach 1 the same speed everywhere?
No. Mach 1 is the local speed of sound, which depends on air temperature. At standard sea-level conditions (15 °C), Mach 1 is about 340.29 m/s or 1,235 km/h, but it is slower in cold air and faster in hot air. The Mach number itself, however, is consistent: Mach 2 always means twice the local speed of sound.
How is running pace related to speed?
Pace and speed are reciprocals. A pace of 5:00 min/km means covering 1 km in 5 minutes, which is 12 km/h. A pace of 4:00 min/km is 15 km/h, and 6:00 min/km is 10 km/h. To convert pace (min/km) to speed (km/h), divide 60 by the pace in minutes; to get pace from speed, divide 60 by the speed.

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