Speed converter

Convert mph to km/h, km/h to mph, m/s, knots and ft/s with exact factors. Includes exact vacuum light speed and an approximate Mach model at sea level.

By Admin Drafted with AI writing toolsUpdated 2 November 2026Checked examples: 5

Converted value

km/h

Significant figures: 12; Nearest, ties away from zero

Conversion: 60 mph = 96.56064 km/h
Conversion factor: 1.609344
Exactness: Exact

60 mph is exactly 96.56064 km/h. One mile per hour is exactly 1.609344 km/h.

The same amount counted in each unit

60 mph in every Speed unit Rows: 8

Unit	Value	Definition
metre per second (m/s)	26.8224	Base unit
kilometre per hour (km/h)	96.56064	1 km/h = 1,000/3,600 m/s, exact
mile per hour (mph)	60	1 mph = 0.44704 m/s, exact
knot (kn)	52.13857	1 kn = 1,852/3,600 m/s, exact
foot per second (ft/s)	88	1 ft/s = 0.3048 m/s, exact
kilometre per second (km/s)	0.0268224	1 km/s = 1,000 m/s, exact
Mach (sea level) (Ma)	0.07882125	1 Ma = 340.294 m/s, approximate (Speed of sound in ISA air at sea level, 15 °C)
speed of light (c)	8.94699 × 10⁻⁸	1 c = 299,792,458 m/s, exact

How it's calculated S

Convert mile per hour to metre per second
$60\ \text{mph} \times 0.44704\ \tfrac{\text{m/s}}{\text{mph}} = 26.8224\ \text{m/s}$
1 mph = 0.44704 m/s, exact
Convert metre per second to kilometre per hour
$26.8224\ \text{m/s} \div \tfrac{1{,}000}{3{,}600}\ \tfrac{\text{m/s}}{\text{km/h}} = 96.56064\ \text{km/h}$
1 km/h = 1,000/3,600 m/s, exact
Combined factor
$1\ \text{mph} = \frac{0.44704}{\tfrac{1{,}000}{3{,}600}}\ \text{km/h} = 1.609344\ \text{km/h}$
Both units are defined exactly and the converted mathematical value has a terminating decimal. A displayed result may still be rounded.

About the speed converter

Each speed unit is a fixed number of metres per second. The road and sea units are exact: a mile per hour is 0.44704 m/s because the mile is 1,609.344 m, a kilometre per hour is 1/3.6 m/s, and a knot, one nautical mile per hour, is 1,852/3,600 m/s.

The default converts 60 mph to 96.56064 km/h, the figure a UK or US driver needs on metric roads. Sailors and pilots work in knots, and 1 knot is exactly 1.852 km/h.

Mach is fixed here at 340.294 m/s, the speed of sound in the International Standard Atmosphere at sea level and 15 °C, and results that use it are marked approximate because the real speed of sound falls with temperature. The speed of light is exactly 299,792,458 m/s by definition.

How to convert mph to km/h

Multiply miles per hour by 1.609344, the exact number of kilometers in a mile: 60 mph × 1.609344 = 96.56064 km/h. The factor works for any speed in statute miles per hour, from road signs to wind reports. To go from km/h to mph, divide by 1.609344.

The factor is exact because the 1959 international yard and pound agreement fixed the yard at 0.9144 m, which makes the mile 1,609.344 m (NIST SP 811, Appendix B.8). Multiplying by 1.6 is a fair mental shortcut that comes out approximately 0.6% low.

How to convert km/h to mph

Multiply km/h by the rounded factor 0.621371, or divide by the exact factor 1.609344. Typical speed limits have these rounded equivalents:

30 km/h ≈ 18.64 mph
50 km/h ≈ 31.07 mph
80 km/h ≈ 49.71 mph
100 km/h ≈ 62.14 mph
120 km/h ≈ 74.56 mph

In the other direction, 30 mph is 48.28 km/h, 50 mph is 80.47 km/h and 70 mph is 112.65 km/h.

Unless explicitly identified as exact, decimal conversions in the prose are rounded approximations.

km/h to m/s: divide by 3.6

A kilometer is 1,000 m and an hour is 3,600 s, so 1 km/h = 1/3.6 m/s. Divide km/h by 3.6 to get m/s: 36 km/h is exactly 10 m/s, and 100 km/h is 27.78 m/s. Multiply m/s by 3.6 to go back.

For US units, 1 m/s is 2.236936 mph or 3.28084 ft/s. A mile per hour is exactly 22/15 ft/s, which makes 60 mph exactly 88 ft/s.

Knots: nautical miles per hour

A knot is one nautical mile, exactly 1,852 m, per hour. So 1 kn = 1.852 km/h, about 1.150779 mph or 0.514444 m/s. Ships, aircraft and marine forecasts use knots: a 30-knot wind is 55.56 km/h or 34.52 mph.

Mach and the speed of light

Mach number compares a speed with the local speed of sound, which falls as air gets colder. For Mach 1, this converter fixes its approximate reference at 340.294 m/s (approximately 1,225.06 km/h or 761.22 mph), the sea-level model value of the standard atmosphere at 15 °C.

That makes every Mach result approximate. At 11 km, where the standard atmosphere is −56.5 °C, sound travels at about 295 m/s, so the same airspeed is a higher Mach number at cruising height.

The speed of light in vacuum, c, is exactly 299,792,458 m/s because the SI defines the meter from it. That is 299,792.458 km/s or 1,079,252,848.8 km/h.

Speed conversion chart

Long decimals are rounded to six places, and the Mach row uses the sea-level value above.

Value	From	To	Converted speed
60	mph	km/h	96.56064
36	km/h	m/s	10
30	kn	km/h	55.56
10	m/s	ft/s	32.808399
1	Ma	km/h	1225.0584
1	c	km/s	299792.458

Common mistakes

Reading knots as mph. A 30 kn wind is 34.52 mph; calling it 30 mph understates it by about 13%.
Using 1.6 where precision matters. 70 mph × 1.6 gives 112 km/h; the exact figure is 112.65408 km/h.
Applying 3.6 the wrong way. 10 m/s is 36 km/h, not 2.78 km/h. For a positive speed, its numerical value in m/s is smaller than its value in km/h. A negative velocity reverses that numerical ordering.

For one direction at a time, use mph to km/h, km/h to mph, knots to mph or m/s to km/h. To find a speed from distance and time, use the kinematics calculator; runners can work in pace per kilometer or mile with the running pace calculator.

Worked examples

60 mph in km/h

Value: 60 mph
From: mile per hour (mph)
To: kilometre per hour (km/h)

Converted value: 96.56064 km/h
Exactness: Exact

Checked against: 60 × 1609.344 m / 1000 = 96.56064 km/h (1 mi = 1609.344 m, NIST HB 44)

1 knot in km/h

Value: 1 kn
From: knot (kn)
To: kilometre per hour (km/h)

Converted value: 1.852 km/h

Checked against: 1 knot = 1 nautical mile per hour = 1852 m/h (NIST SP 811 App. B)

100 km/h in m/s

Value: 100 km/h
From: kilometre per hour (km/h)
To: metre per second (m/s)

Converted value: 27.7777777778 m/s
Exactness: Exact definitions, repeating decimal

Checked against: 100000 m / 3600 s = 250/9

Speed of light in km/s

Value: 1 c
From: speed of light (c)
To: kilometre per second (km/s)

Converted value: 299,792.458 km/s

Checked against: c = 299,792,458 m/s exactly (SI definition of the metre)

Questions

How do I convert mph to km/h?

Multiply by 1.609344: 60 mph × 1.609344 = 96.56064 km/h, and 70 mph is approximately 112.65 km/h. The factor is exact because a mile is exactly 1,609.344 m. Multiplying by 1.6 is a mental shortcut that comes out approximately 0.6% low; to go from km/h to mph, multiply by the rounded factor 0.621371.

How do I convert km/h to m/s?

Divide by 3.6, because an hour has 3,600 seconds and a kilometre 1,000 metres. 100 km/h is approximately 27.78 m/s and 36 km/h is exactly 10 m/s. Multiply by 3.6 to go back: a sprinter at 10 m/s is running 36 km/h, or approximately 22.37 mph.

What is a knot in mph and km/h?

One knot is exactly 1.852 km/h, about 1.15078 mph or 0.514444 m/s. It is one nautical mile (1,852 m) per hour, the speed unit of shipping and aviation, so a 30-knot wind is exactly 55.56 km/h or approximately 34.52 mph.

How fast is Mach 1?

In the International Standard Atmosphere at sea level (15 °C), this converter uses a fixed reference of 340.294 m/s, corresponding to approximately 1,225.06 km/h or 761.22 mph. The speed of sound depends on air temperature. In the separate standard-atmosphere example at 11 km altitude and −56.5 °C, Mach 1 is about 295 m/s or 1,062 km/h.

Why is the speed of light an exact number?

Because the metre is defined from it. Since 1983 the metre has been the distance light travels in vacuum in 1/299,792,458 of a second, which fixes c at exactly 299,792,458 m/s, or 1,079,252,848.8 km/h. Conversions from c into units defined by exact factors retain that exactness. A result in Mach remains approximate because this app uses a fixed atmospheric reference.

About this calculator

\begin{gathered} x_{\text{to}} = x_{\text{from}} \times \dfrac{f_{\text{from}}}{f_{\text{to}}} \\ f = \text{one unit expressed in } \text{m/s} \end{gathered}

Sources

Checked against references

This calculator includes 5 worked examples with independently sourced answers. They run in the test suite, and you can run them here too.

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