Speed Converter
Convert speed between mph, km/h, m/s, knots and ft/s instantly.
What this tool does
To convert speed, multiply by the exact factor between the two units - 100 km/h is about 62.14 mph, and 1 knot is exactly 1.852 km/h. This tool converts between five units at once - metres per second, kilometres per hour, miles per hour, knots, and feet per second - and shows the exact factor used alongside the result.
Converts speed between five units - metres per second, kilometres per hour, miles per hour, knots and feet per second.
Shows the exact conversion factor used for every result.
How to use it
- Enter the speed you want to convert.
- Pick the unit you're converting from and the unit you're converting to.
- Read the result, or press Swap units to reverse it.
Why use this converter
Speed limits, wind forecasts, race results and aircraft speeds use km/h, mph, m/s and knots depending on where and what, and a quick mental conversion is approximate at best.
Why we built it
We built the speed converter to explain why speed factors combine a distance and a time. For popular pairs use the mph to km/h converter and the knots to mph converter.
For a neighbouring job there is also the Time Unit Converter and the Data Transfer Rate Converter.
If your task goes further, try the Acceleration Calculator.
Who this tool is for
- Drivers and cyclists abroad
- Sailors, pilots and weather watchers
- Students
When to use it
- Reading road signs or vehicle specs from another country.
- Interpreting wind and sailing or aviation forecasts in knots.
- Converting running, cycling or sport speeds.
- Science and engineering problems in m/s.
Speed is a length unit divided by a time unit
Which is why the conversion factors look less tidy than length alone.
Every speed unit combines a distance and a time: kilometres per hour, miles per hour, metres per second. Converting between them means handling both parts at once - km/h to m/s, for instance, divides by 3.6, because there are 3.6 kilometres in each 3,600-second hour once you work through the unit conversion. That combined factor is why speed conversions aren't as immediately obvious as pure length or weight ones, even though the underlying length and time units are the same familiar ones used elsewhere.
The knot: still standard in sea and air navigation
A knot is one nautical mile per hour, and since a nautical mile is defined as exactly 1,852 metres, a knot is exactly 1.852 km/h. Knots remain the standard speed unit in marine and aviation navigation worldwide, including in countries that otherwise use kilometres for everything else, because it's tied directly to a minute of latitude - which makes it genuinely useful for chart-based navigation in a way an arbitrary metric unit isn't.
What you give it, and what you get back
| Item | Details |
|---|---|
| Value | A speed in the "from" unit. |
| From and To | m/s, km/h, mph, knots or ft/s. |
| Output | The converted speed and the factor used. |
Issues you may run into
| What you see | Why it happens | What to do |
|---|---|---|
| Pace is confused with speed | Pace is time per distance, speed is distance per time. | Use the pace calculator for min/km. |
| Knots look unfamiliar | A knot is one nautical mile per hour. | It equals about 1.852 km/h. |
| Round numbers do not match | Display rounding. | The factors are exact. |
Assumptions and limitations
- This converts a rate of speed. It does not calculate travel time or distance from speed - for that, use a dedicated time/distance/speed calculator.
- Speed limits and legal driving figures vary by country's own posted units (mph or km/h) - this tool converts the number, but always follow the units actually posted where you're driving.
- Very small or very large results are shown with practical rounding for readability; the internal calculation is exact.
Frequently asked questions
How do I convert mph to km/h?
Multiply by 1.609344 - the same exact factor used for converting miles to kilometres, since mph and km/h both use the same underlying mile-to-kilometre relationship, just per hour instead of as a plain distance.
How many km/h is 100 mph?
About 160.93 km/h (100 × 1.609344). This tool gives the exact figure instantly for any speed, not just round numbers.
What is a knot in km/h?
Exactly 1.852 km/h. A knot is one nautical mile (1,852 metres, a defined constant) per hour, which is why the conversion is a clean, exact number rather than an approximation.
How do I convert km/h to m/s?
Divide by 3.6. This comes from converting 1 kilometre (1,000 m) per 1 hour (3,600 s): 1,000 ÷ 3,600 = 0.2778 m/s per km/h, so dividing by 3.6 does the same thing as multiplying by that figure.
Why do pilots and sailors use knots instead of mph or km/h?
Because a knot is directly tied to a nautical mile, which is defined from a minute of latitude on a navigation chart - one knot of speed for one hour covers one minute of latitude, which is genuinely useful for plotting a course, unlike an arbitrary land-based unit.
Are speed conversion factors here exact?
Yes. They're built directly from the exact length definitions (the 1,609.344 m mile, the 1,852 m nautical mile, the 0.3048 m foot) divided by the exact number of seconds in an hour, so nothing here is a rounded approximation.
Sources and accuracy
Exact internationally defined constants: the mile (1609.344 m) and nautical mile (1852 m) underlying mph and knots respectively.
Figures last checked against the source on . Standards and rates can change — if you are relying on this for something that matters, confirm against the source above. Think a figure is wrong or out of date? Send a correction.