Speed Converter
Convert speed between km/h, mph, m/s, knots, and ft/s. Enter ordinary decimals, grouped values, or scientific notation, reverse the conversion with Swap, and copy results displayed with up to four decimal places.
Enter a non-negative value.
Enter a speed value.
Choose the source and target units to see the conversion.
How to Use the Speed Converter
Enter a non-negative speed, select the source unit, and choose the unit you want to convert to.
Use Swap to reverse the direction. When a valid result exists, the converted value becomes the new source value without relying on the visibly rounded result.
The input supports ordinary decimals, grouped values such as 1,000, and scientific notation such as 2.5e3.
How Speed Unit Conversion Works
Each supported unit has a factor representing the number of metres per second in one unit.
The source value is multiplied by its metres-per-second factor and divided by the target factor.
Using metres per second as the common reference avoids chaining rounded conversions between mph, km/h, knots, and ft/s.
Supported speed units
Swipe horizontally to view the full table.
Metres per Second
The metre per second, symbol m/s, is the coherent SI derived unit of speed and velocity.
A speed of one metre per second means covering one metre during one second.
Metres per second are widely used in physics, engineering, meteorology, fluid mechanics, and scientific calculations.
Kilometres per Hour
A kilometre per hour, symbol km/h, means travelling one kilometre during one hour.
Because one kilometre is 1,000 metres and one hour is 3,600 seconds, one km/h equals exactly 5/18 m/s.
The reverse relationship is also exact: one metre per second equals 3.6 km/h.
Miles per Hour
Miles per hour, symbol mph, expresses international miles travelled during one hour.
The international mile equals exactly 1,609.344 metres, so one mph equals exactly 0.44704 m/s.
Miles per hour remain common for road speeds and vehicle displays in the United States and United Kingdom.
Knots
One knot is one international nautical mile per hour.
The international nautical mile equals exactly 1,852 metres, making one knot exactly 1.852 km/h or 463/900 m/s.
Knots are standard in marine navigation and widely used in aviation and weather reporting.
The correct symbol is kn. Writing knots per hour would be incorrect because a knot already means a nautical mile per hour.
Feet per Second
Feet per second, symbol ft/s, expresses international feet travelled during one second.
The international foot equals exactly 0.3048 metres, so one ft/s equals exactly 0.3048 m/s.
Feet per second appear in engineering, flow measurements, ballistics, sports measurements, and technical specifications.
Speed Versus Velocity
Speed describes how quickly distance is covered and has magnitude only.
Velocity includes direction. Two objects can have the same speed while having different velocities because they move in different directions.
This converter changes a non-negative speed magnitude. It does not convert directional vectors or calculate resultant velocity.
Where Different Speed Units Are Used
The most useful speed unit depends on the field, location, instrument, and reporting convention.
Unit conversion changes only the numerical representation. It does not change whether an aviation value is indicated airspeed, true airspeed, or ground speed.
Typical speed units by context
Swipe horizontally to view the full table.
Common Speed Conversions
The table uses the same exact factors as the live converter.
Results that do not terminate are rounded to no more than four decimal places.
Common speed conversion table
Swipe horizontally to view the full table.
Why Mach Is Not a Fixed Conversion Unit
Mach number is the ratio between an object's speed and the local speed of sound.
The local speed of sound depends on the medium and conditions including temperature.
A fixed Mach-to-mph or Mach-to-km/h factor would therefore require an assumed atmosphere and temperature. This converter includes only units with fixed relationships.
Precision and Rounding
The underlying length and time relationships used here are exact.
Ordinary results display up to four decimal places with unnecessary trailing zeros removed. Scientific notation is used when fixed decimals would be impractical.
An exact conversion factor does not make a measured speed exact. Instrument resolution, calibration, source rounding, averaging, and measurement conditions still determine practical accuracy.
Speed Conversion Is Not a Travel-Time Calculation
Travel time can be estimated by dividing distance by average speed when both remain compatible.
Real trips can include changing speed, stops, traffic, wind, currents, routes, and acceleration.
This tool converts a speed value only and does not estimate journey duration or arrival time.
Privacy and Local Processing
Speed conversion runs entirely in the browser.
The entered value and selected units are not uploaded, added to a public URL, or permanently stored.
Clipboard access is requested only when the result copy control is used.
Speed Conversion Formulas
Every supported unit is represented by its exact metres-per-second factor.
Formula variables
- Speed in the selected source unit
- Speed in the selected target unit
- Metres per second represented by one source unit
- Metres per second represented by one target unit
Examples
Convert road speed from km/h to mph
1Input
100 km/h
Show result
Result
62.1371 mph
Convert road speed from mph to km/h
2Input
60 mph
Show result
Result
96.5606 km/h
Convert metres per second to km/h
3Input
20 m/s
Show result
Result
72 km/h
Convert marine speed
4Input
10 kn
Show result
Result
18.52 km/h
Convert knots to mph
5Input
25 kn
Show result
Result
28.7695 mph
Convert feet per second
6Input
30 ft/s
Show result
Result
20.4545 mph
Frequently Asked Questions
How fast is 100 km/h in mph?
100 kilometres per hour is approximately 62.1371 miles per hour.
How fast is 60 mph in km/h?
60 miles per hour is approximately 96.5606 kilometres per hour.
How do I convert km/h to mph?
Multiply km/h by approximately 0.621371, or convert through metres per second using the exact factors.
How do I convert mph to km/h?
Multiply mph by exactly 1.609344.
How do I convert m/s to km/h?
Multiply metres per second by exactly 3.6.
How do I convert km/h to m/s?
Multiply kilometres per hour by 5/18, or divide by 3.6.
What is one knot in km/h?
One knot equals exactly 1.852 km/h.
What is one knot in mph?
One knot is approximately 1.1508 mph.
Why are knots used at sea?
A knot is one nautical mile per hour. Nautical miles are established navigation units used for marine and aviation distances.
Is speed the same as velocity?
No. Speed has magnitude only, while velocity also includes direction.
Why is Mach not included?
Mach is a ratio to the local speed of sound. Since the speed of sound changes with the medium and temperature, Mach does not have one fixed conversion factor.
Can speed be negative?
Speed is normally expressed as a non-negative magnitude. A negative value may represent a chosen direction in a velocity calculation, which this converter does not perform.
Does this calculate journey time?
No. It converts speed units only and does not account for distance, stops, changing speed, traffic, wind, or route conditions.
Can I enter scientific notation?
Yes. Values such as 2.5e3 and 1e-4 are supported.
Are my speed values uploaded?
No. Conversion happens locally in the browser.
References
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