Speed Converter

Convert speed between metres per second, kilometres per hour, miles per hour, feet per second, knots, and Mach, with all six units shown at once.

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Speed

Convert speed between mph, km/h, m/s, knots, and Mach

Enter a speed and choose a unit — all six speed units are shown at once: metres per second, kilometres per hour, miles per hour, feet per second, knots, and Mach.

Metres per second

27.7778m/s

Kilometres per hour

100km/h

Miles per hour

62.1371mph

Feet per second

91.1344ft/s

Knots

53.9957kn

Mach (at sea level)

0.0816Ma

Quick reference

  • 1 mph = 1.60934 km/h = 0.44704 m/s
  • 1 km/h = 0.62137 mph = 0.27778 m/s
  • 1 knot = 1.852 km/h = 1.15078 mph
  • Speed of sound ≈ 340 m/s (Mach 1)
  • 100 km/h ≈ 62.1 mph
  • 60 mph ≈ 96.6 km/h

Speed

Speed conversion: mph, km/h, m/s, knots, and Mach explained

A speed converter translates any speed value into all common units at once. This tool covers metres per second, kilometres per hour, miles per hour, feet per second, knots, and Mach — the units used across road travel, aviation, maritime navigation, and science.

The main speed units and where each is used

Kilometres per hour (km/h) is the standard unit for road speed in most countries. Miles per hour (mph) is used on roads in the US, UK, and a small number of other countries. Metres per second (m/s) is the SI unit and is used in physics, engineering, and meteorology. Knots (nautical miles per hour) are used in aviation and maritime navigation. Feet per second (ft/s) appears in some US engineering and ballistics contexts. Mach number expresses speed as a multiple of the speed of sound and is used in aviation and aerospace.

The speed of sound at sea level in dry air at 15°C is approximately 340.29 m/s (1,225 km/h, 761 mph) — this is the reference value used for Mach 1 in this converter. Note that the actual speed of sound varies with altitude, temperature, and humidity; the Mach conversion here uses the ISA sea-level standard.

Key conversion factors

1 mph = 1.60934 km/h = 0.44704 m/s exactly. 1 km/h = 0.27778 m/s = 0.62137 mph. 1 knot = 1.852 km/h exactly = 1.15078 mph. 1 ft/s = 0.3048 m/s exactly (same definition as feet to metres). The mph-to-km/h factor (1.60934) is derived from the exact mile definition: 1 mile = 1,609.344 m.

For everyday mental arithmetic: to convert mph to km/h, multiply by 1.6 (rough) or 1.609 (more accurate). To convert km/h to mph, multiply by 0.6 (rough) or 0.621 (more accurate). 100 km/h ≈ 62 mph; 60 mph ≈ 97 km/h; 130 km/h ≈ 81 mph (common European motorway speed limit).

Knots and maritime/aviation speed

A knot is defined as one nautical mile per hour. One nautical mile equals 1,852 metres exactly (one arc-minute of latitude). Knots are used because the nautical mile connects directly to chart navigation: a speed of 10 knots means 10 nautical miles covered per hour, which maps directly to degrees and minutes of latitude.

Aircraft speeds are reported in knots (true airspeed, indicated airspeed) and in Mach numbers at high altitude. Ground speeds appear in knots on navigation displays. Converting between knots and km/h or mph is needed when cross-referencing aviation data with road or weather contexts.

Using this converter for travel, weather, and science

Travel: use the mph ↔ km/h conversion when driving or reading speed limits in a foreign country. Weather: wind speeds are reported in km/h, mph, or knots depending on the country and service — this converter covers all three. Science and engineering: m/s is the standard for calculations; use this converter to contextualise real-world measurements.

When comparing vehicle specifications across markets, note that speedometers in km/h countries show a different number for the same speed as mph-market cars. This converter shows both simultaneously so you can cross-reference without mental arithmetic.

Frequently asked questions

How do I convert mph to km/h?

Multiply mph by 1.60934 to get km/h. For example, 60 mph × 1.60934 = 96.56 km/h. The reverse is km/h × 0.62137 = mph. Both factors derive from 1 mile = 1,609.344 metres exactly.

 What is a knot in km/h or mph?

1 knot = 1.852 km/h exactly, or approximately 1.151 mph. A vessel or aircraft travelling at 20 knots is doing 37.04 km/h or 23.02 mph.

 What is Mach 1 in km/h and mph?

At sea level in standard atmospheric conditions (15°C, 1 atm), Mach 1 ≈ 340.29 m/s ≈ 1,225 km/h ≈ 761 mph. At higher altitudes where air is colder and thinner, the speed of sound is lower — Mach 1 at cruise altitude (around 10–12 km) is approximately 295 m/s or 1,062 km/h.

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