Speed Converter
Road speeds are often written in km/h, U.S. and UK vehicle references use mph, science and wind data use m/s, and marine or aviation contexts use knots. Enter a value, choose the source unit and target unit, and the tool shows the main result, all unit equivalents, and estimated times for 100 m, 1 km, and 1 mile.
Speed
Result
ready to use.
- Visible firstKeep the input and result positions clear.
- Results firstPut the main number up front and keep the process secondary.
- Less to askNo sign-up or extra information before using the tool.
Read speed units and travel-time cues in one place
The speed converter rewrites the same pace in another unit. It helps when you need to compare 100 km/h with mph, check what 20 knots means on a road-speed scale, or turn 10 m/s into a value used in training, weather, or engineering notes.
This page first normalizes the input to km/h, then converts it to the selected display unit. Because miles, nautical miles, feet, and SI meters have fixed relationships, the calculation path stays consistent even when the unit names come from different fields.
Use it in screen order
- Enter the speed value first. If you type 100, the tool reads it as 100 in the source unit currently selected.
- Choose the source unit: km/h for most road signs, mph for U.S. and some UK references, m/s for wind or sensor data, and knots for marine or aviation speeds.
- Choose the unit you want to display. The large result updates first, and the comparison grid below keeps the other units visible.
- Decimal places only change the displayed rounding. They do not change the conversion constants used in the calculation.
Examples and distance feel
Speed units are easier to read when the converted number is shown with a distance cue. The same value can feel different when you compare it with 100 m, 1 km, or 1 mile.
Where each unit appears
- km/h is the everyday road and vehicle-speed unit in most metric countries.
- mph appears in U.S. road signs, many UK road contexts, vehicle specifications, and international articles. One statute mile is exactly 1.609344 km.
- m/s means meters per second. It is common in physics, engineering, wind speed, sensor readings, and performance data.
- knot means one nautical mile per hour. Marine and aviation navigation use nautical miles, so knots remain a separate speed unit.
- ft/s means feet per second. It appears in ballistics, falling-object examples, some fluid or engineering data, and U.S. customary-unit references.
Rounding and cautions
- For speed limits, operations, and safety decisions, follow the local rule or the measuring device rather than a rounded calculator display.
- The distance times assume the speed stays constant. They do not include acceleration, braking, stops, traffic lights, wind, or slope.
- Fewer decimal places make the result easier to read, but always keep the source and target units next to the number.
- Knots and mph can both look like “miles,” but knots use nautical miles while mph uses statute miles.
FAQ
What factor converts mph and km/h?
Use 1 mph = 1.609344 km/h. A statute mile is 5,280 ft, and the international foot is exactly 0.3048 m, so 1 mile is exactly 1.609344 km.
Why are knots separate from mph?
A knot is a marine and aviation speed unit. 1 knot means moving 1 nautical mile in one hour, and 1 nautical mile is exactly 1,852 m.
How do I convert m/s to km/h?
1 m/s means moving 1 meter every second. Since an hour has 3,600 seconds, 1 m/s = 3,600 m/h = 3.6 km/h.
When is ft/s used?
ft/s means feet per second. It is less common on road signs, but appears in falling-object examples, ballistics, fluid flow, and some U.S. customary engineering references.
Are the travel times actual arrival times?
No. The 100 m, 1 km, and 1 mile times are reference values that assume a constant speed. Real trips include stops, acceleration, traffic, slope, wind, and route conditions.
Reference used
The constants follow NIST Handbook 44 Appendix C for SI meters, international feet, statute miles, and nautical miles, then derive mph, knots, and ft/s from those relationships.