Speed Converter

What is a speed converter?

A speed converter changes a speed from one unit into every other unit at once — kilometres per hour (km/h), miles per hour (mph), metres per second (m/s), feet per second (ft/s) and knots (kn). Instead of remembering a dozen separate conversion factors, you enter one value, pick its unit, and read all five equivalents side by side.

Speed (or more precisely, speed magnitude) is distance divided by time. Because the same physical motion can be described with different distance and time units, the underlying value never changes — only the label on it does. This tool handles that relabelling with exact, internationally agreed factors so the numbers stay accurate to seven significant figures.

How does this speed converter work?

It converts your value to a single base unit — metres per second (m/s) — and then divides by each target unit’s value in m/s. This base-unit method means every conversion uses the same two simple steps, which keeps results consistent and removes rounding drift from chaining conversions.

The exact factor for each unit (its value in metres per second) is:

Unit	Symbol	Value in m/s (factor)
Metres per second	m/s	1
Kilometres per hour	km/h	1 / 3.6 = 0.2777778
Miles per hour	mph	0.44704
Feet per second	ft/s	0.3048
Knots	kn	0.514444

The two-step formula is:

metres_per_second = value × factor_of_from_unit result = metres_per_second ÷ factor_of_target_unit

So to go directly from one unit to another, you multiply by the ratio of the two factors. For km/h to mph that ratio is 0.2777778 ÷ 0.44704 = 0.621371, the familiar km/h-to-mph multiplier.

How do you convert km/h to mph (worked example)?

Multiply km/h by 0.621371, or follow the base-unit steps for full precision. 100 km/h equals about 62.14 mph.

Step by step for 100 km/h:

1. To m/s: 100 × 0.2777778 = 27.77778 m/s
2. To mph: 27.77778 ÷ 0.44704 = 62.13712 mph
3. To ft/s: 27.77778 ÷ 0.3048 = 91.13444 ft/s
4. To knots: 27.77778 ÷ 0.514444 = 53.99573 kn

These match the converter’s output exactly. So a car cruising at 100 km/h is travelling roughly 62 mph, just under 28 m/s, and about 54 knots.

How do you convert mph to km/h (worked example)?

Multiply mph by 1.609344, or use the base unit. 60 mph equals about 96.56 km/h.

Step by step for 60 mph:

1. To m/s: 60 × 0.44704 = 26.8224 m/s
2. To km/h: 26.8224 ÷ 0.2777778 = 96.56064 km/h
3. To knots: 26.8224 ÷ 0.514444 = 52.13862 kn
4. To ft/s: 26.8224 ÷ 0.3048 = 88 ft/s

That last line is a tidy classic: exactly 60 mph is 88 feet per second, which is why physics problems often use 88 ft/s.

What is a knot, and why is it different?

A knot is one nautical mile per hour, equal to exactly 1.852 km/h, about 1.151 mph, or 0.514444 m/s. A nautical mile is based on the geometry of the Earth — one minute of latitude — which makes knots the natural unit for navigation by sea and air, where charts are marked in degrees and minutes.

The name comes from old sailing practice: sailors trailed a rope (a “log line”) knotted at regular intervals and counted how many knots passed through their hands in a fixed time to estimate speed. Today, knots remain standard in aviation, maritime shipping, and meteorology (wind speed in forecasts is usually reported in knots).

What is the quick km/h to mph reference table?

For everyday driving and travel, these rounded equivalents cover the most common limits. Use them as a sanity check against the converter:

km/h	mph	m/s	knots
30	18.64	8.33	16.20
50	31.07	13.89	26.998
80	49.71	22.22	43.20
100	62.14	27.78	53.996
120	74.56	33.33	64.79
130	80.78	36.11	70.19

A handy rule of thumb: to estimate mph from km/h, take about 60 percent of the km/h figure. For the reverse, multiply mph by roughly 1.6.

What are common use cases for a speed converter?

• Driving abroad: read a km/h speed limit when your car shows mph (or vice versa).
• Running and cycling: convert pace and speed between m/s, km/h and mph for training apps.
• Physics and engineering: convert measured speeds to m/s, the SI base unit, before plugging into formulas.
• Sailing and aviation: translate knots into km/h or mph for friends who do not use nautical units.
• Weather: turn forecast wind speeds (often in knots or km/h) into a unit you find intuitive.

If you work with distance and time separately, the length converter handles the distance side, and you can browse more tools on the converters category page. For ratio-style comparisons of two values, the ratio calculator is a useful companion.

What mistakes and limitations should you watch for?

The most common error is mixing up the direction of the factor — multiplying when you should divide. Because km/h to mph (×0.621371) and mph to km/h (×1.609344) look similar, it is easy to apply the wrong one; the base-unit method above avoids this entirely. Another frequent slip is confusing knots with km/h: they are close in feel but not equal, and a knot is the larger unit.

Keep these limits in mind:

• This converter handles constant speed magnitude only — it does not account for velocity as a vector (direction), acceleration, or wind and current effects on a vehicle.
• It assumes the international definitions (statute mile, international foot, nautical mile of 1852 m). Historical or country-specific miles differ slightly.
• Results are shown to seven significant figures, so very small or very large inputs may round in the final displayed digit.
• For legal, navigational, or safety-critical work, always confirm against the official figure for your jurisdiction or instrument; this tool is for general reference and estimation.