Speed Converter
Convert speeds between km/h, mph, m/s and more, with running pace where available.
Enter a nonnegative number, for example 1.5. Decimal notation and exponents are supported; see Method for input limits.
Rounded display; exact calculation retained until you edit
-
Rounded display
Batch: Auto uses the locale decimal convention with dot fallback; List splits commas/whitespace and uses dot decimals. Dot supports 1,234.5; Comma supports 1.234,5 with complete three-digit grouping only. Newline, semicolon and tab separate entries. Text cap 65536 UTF-16 units; candidate cap 300 speed / 500 volume includes invalid entries. Invalid/excess entries are omitted from exports with counts; no valid rows means no export.
- : —
Method
Convert speed through exact m/s factors: 1 mph = 1.609344 km/h, 36 km/h = 10 m/s, 1 knot = 1852/3600 m/s. Mach uses a fixed approximate 340.294 m/s for dry air near 15°C; the atmospheric reference table is illustrative, not an adjustable model. Pace is distance divided by speed, rounded once to seconds: 12 km/h gives 5:00/km and 8:03/mile. Pace is undefined at zero and only displayed for 0.1 < km/h < 500. Road and vehicle examples are illustrative, not current law or attainable-speed claims.
Scalar input: at most 256 UTF-16 units, 100 significant digits and exponent −100…100. Use complete decimal numbers; no suffixes or grouping in single mode. Dot is decimal; a decimal comma is also accepted only in comma-decimal locales. Negative quantities are rejected; zero is valid, empty is not zero.
Presentation rounds half away from zero. Storage uses at most 2/4/6/8 fractional places; other linear results use 8 significant digits, scientific below 0.0001 or at/above 1e15 for nonintegers. Exact integers stay complete. Copy/export uses ungrouped dot decimals. Computation is local except the currency rate request; surrounding site requests still exist.
Copied
Copy failed. Select the result and copy it manually.
How do you convert km/h to mph and mph to km/h?
Both directions use the same exact factor: 1.609344 kilometres per statute mile, fixed by the 1959 international yard and pound agreement. Going from km/h to mph you divide — 130 ÷ 1.609344 = 80.78 mph — and going from mph to km/h you multiply — 65 × 1.609344 = 104.61 km/h. Because the factor is exact, the only rounding is the one you choose for the answer; this converter carries eight significant figures, far more than any speedometer or radar gun resolves. Without a calculator, remember that mph is roughly 62% of the km/h figure and km/h is roughly 1.6 times mph.
What are the exact speed conversion factors?
Exact factors connect the units through m/s: 1 mph = 1.609344 km/h; 1 knot = 1852/3600 m/s. Display rounding does not change these definitions.
| Unit | km/h | mph | m/s | Accuracy |
|---|---|---|---|---|
| 1 km/h | 1 | 0.621371 | 0.277778 | Rounded display |
| 1 mph | 1.609344 | 1 | 0.44704 | Rounded display |
| 1 m/s | 3.6 | 2.236936 | 1 | Rounded display |
| 1 ft/s | 1.09728 | 0.681818 | 0.3048 | Rounded display |
| 1 knot (kn) | 1.852 | 1.150779 | 0.514444 | Rounded display |
| 1 cm/s | 0.036 | 0.022369 | 0.01 | Rounded display |
| 1 km/s | 3 600 | 2 236.94 | 1 000 | Rounded display |
| Mach 1 (sea level, 15 °C) | 1 225.06 | 761.22 | 340.29 | Rounded display |
| c (speed of light) | 1.0793 × 10⁹ | 6.7062 × 10⁸ | 299 792 458 | Rounded display |
What do common speeds look like in every unit?
These physical and vehicle speeds are illustrative comparisons, not records or promises of attainable speed.
| Speed | km/h | mph | m/s | kn |
|---|---|---|---|---|
| Brisk walk | 5 | 3.11 | 1.39 | 2.70 |
| Easy jog | 10 | 6.21 | 2.78 | 5.40 |
| Marathon world-record pace | 21.0 | 13.05 | 5.83 | 11.34 |
| Recreational cyclist | 25 | 15.53 | 6.94 | 13.50 |
| 100 m sprint, peak speed | 44.7 | 27.78 | 12.42 | 24.14 |
| Default European city limit | 50 | 31.07 | 13.89 | 27.00 |
| Motorway cruising | 120 | 74.56 | 33.33 | 64.79 |
| Airliner at cruise | 900 | 559.23 | 250.0 | 485.96 |
| Speed of sound at sea level | 1 225.1 | 761.22 | 340.29 | 661.48 |
| Low Earth orbit | 27 600 | 17 150 | 7 667 | 14 903 |
How do posted speed limits compare in km/h and mph?
The posted-sign values below illustrate unit conversion only. They are not current legal limits; check the actual signs and local rules.
| Posted sign | km/h | mph | Where you typically see it |
|---|---|---|---|
| 30 km/h | 30 | 18.6 | City centres, school zones and residential streets across the EU |
| 25 mph | 40.2 | 25 | Typical US residential street limit |
| 50 km/h | 50 | 31.1 | Default built-up-area limit in most of Europe |
| 55 mph | 88.5 | 55 | Common US rural highway limit |
| 90 km/h | 90 | 55.9 | Rural single-carriageway roads in many EU countries |
| 65 mph | 104.6 | 65 | Common US interstate limit |
| 70 mph | 112.7 | 70 | UK motorway limit; many US interstates |
| 120 km/h | 120 | 74.6 | Motorway limit in Spain, Portugal and Belgium |
| 130 km/h | 130 | 80.8 | Motorway limit in France, Italy and Austria |
| 140 km/h | 140 | 87.0 | Motorway limit in Poland and Bulgaria |
How do you convert speed to running or cycling pace?
Pace is time per distance: 12 km/h gives 5:00/km and 8:03/mile after rounding to seconds. It is undefined at zero; this tool displays it only for 0.1 < km/h < 500.
| km/h | mph | min/km | min/mile |
|---|---|---|---|
| 8 | 4.97 | 7:30 | 12:04 |
| 10 | 6.21 | 6:00 | 9:39 |
| 12 | 7.46 | 5:00 | 8:03 |
| 14 | 8.70 | 4:17 | 6:54 |
| 16 | 9.94 | 3:45 | 6:02 |
| 18 | 11.18 | 3:20 | 5:22 |
| 20 | 12.43 | 3:00 | 4:50 |
| 25 | 15.53 | 2:24 | 3:52 |
| 30 | 18.64 | 2:00 | 3:13 |
What is a knot, and why do ships and aircraft use it?
A knot is one nautical mile per hour. The nautical mile is defined as exactly 1,852 metres, which is close to one minute of arc of latitude, so a navigator can measure distance straight off the latitude scale at the side of a chart and divide by speed in knots to get hours. That is why aviation and marine practice keeps knots and nautical miles together: airspeed, ground speed and reported wind in a METAR are all in knots, while European marine forecasts often give wind in m/s instead. One knot is 1.852 km/h, 1.15078 mph or 0.514444 m/s, and 20 m/s of wind is 38.88 knots.
How fast is Mach 1 at different altitudes?
Mach here uses a fixed approximate 340.294 m/s near 15°C. The altitude table illustrates atmospheric variation; changing altitude does not adjust the converter.
| Altitude | ISA temperature | Mach 1 (km/h) | (mph) |
|---|---|---|---|
| 0 m | 15.0 °C | 1 225.1 | 761.2 |
| 3 000 m | −4.5 °C | 1 182.9 | 735.0 |
| 6 000 m | −24.0 °C | 1 139.1 | 707.8 |
| 9 000 m | −43.5 °C | 1 093.7 | 679.6 |
| 11 000 m | −56.5 °C | 1 062.3 | 660.1 |
What is the formula for speed?
Speed is distance divided by time: v = d / t. Keep the two inputs in matching units and the answer carries them — 400 metres in 50 seconds is 8 m/s, 240 kilometres in 3 hours is 80 km/h, 26.2 miles in 3 hours is 8.73 mph. Convert only after the division, using a single factor, so rounding happens once: 8 m/s × 3.6 = 28.8 km/h. Two traps are worth remembering. Average speed is total distance over total time, not the mean of the leg speeds — driving 60 km at 60 km/h and 60 km at 120 km/h averages 80 km/h, not 90. And speed is a magnitude while velocity carries a direction, so a lap of a track has a high average speed and zero average velocity.
Sources
The conversion factors on this page come from the primary definitions rather than from other converters. These are the documents they are taken from:
- NIST Special Publication 811 — Guide for the Use of the International System of Units (SI), Appendix B conversion factors
- BIPM — The International System of Units (SI Brochure), 9th edition, including non-SI units accepted for use with the SI
- NOAA Ocean Service — What is the difference between a nautical mile and a knot?
- NIST — Definition of the metre from the fixed speed of light, 299,792,458 m/s
About Speed Converter
Speed is the one everyday quantity that changes units at every border. A rental car in France shows 130 on the motorway sign, an American driver thinks in 80 mph, a physics problem wants 36.1 m/s, an air traffic controller reads 70 knots of ground speed and a runner wants to know what all of that means in minutes per kilometre. This speed converter holds all of those views of the same number in one place: type a value once, pick the unit it is in, and km/h, mph, m/s, ft/s, knots, cm/s, km/s, Mach and fractions of the speed of light appear together, with the running and cycling pace underneath.
Everything is scaled through metres per second as an internal base, using the defined factors rather than rounded shortcuts: the statute mile has been exactly 1,609.344 m since the 1959 international yard and pound agreement, the nautical mile is exactly 1,852 m, and the foot is exactly 0.3048 m, so the factors are exact while displayed quotients may be rounded. Only one row is physical rather than definitional: Mach is a ratio against the local speed of sound, quoted here for the ISA standard atmosphere at sea level (15 °C, 340.29 m/s). The speed of light row uses the defined constant 299,792,458 m/s. Where this page stops being a lookup and starts being a tool is batch mode.
Paste a column of speeds — GPS traces, lap times from a stopwatch app, wind readings from a weather station, telemetry exported from a bike computer — and every value is converted into five units plus both pace columns in a single table you can copy as tab-separated text or download as a CSV. The reference tables below cover the exact factors, common speeds from a brisk walk to low Earth orbit, illustrative posted-speed examples in both systems, a pace chart and the speed of sound at cruising altitude, so you can check the arithmetic without trusting a black box.
36 km/h = 10 m/s; 12 km/h → 5:00/km; 8:03/mile
Model · Rounded display
Use Cases
How to use
Type the speed into the Value field. Decimals such as 27.8 and scientific notation are both accepted.
Choose the unit that number is already in: km/h, mph, m/s, ft/s, knots, cm/s, km/s, Mach or c.
Read every other unit in the results list; the row matching your input unit is highlighted, and the pace in min/km and min/mile is shown underneath.
Copy a single value with the copy icon, use Copy as table to take the whole conversion, or press the arrows on a row to convert onward from that result.
Switch to Batch mode to convert a whole column of speeds at once and export the grid as CSV.
Pro Tips
- Mental shortcut for km/h to mph: multiply by 5 and divide by 8. For 100 km/h that gives 62.5 mph against the rounded 62.14 mph, about 0.6% high. Reverse it — times 8, divided by 5 — to read an mph sign in km/h.
- Divide km/h by 3.6 to get m/s. 36, 72 and 108 km/h are exactly 10, 20 and 30 m/s — handy checkpoints.
- A knot already contains the hour (1 nautical mile per hour = 1.852 km/h), so “knots per hour” is never correct.
- Mach depends on air temperature, not on altitude directly. The Mach row here uses the 15 °C sea-level value, 1,225.06 km/h.
- Click the ⇄ arrows on any result row to make that value the new input — the fastest way to chain km/h → knots → m/s.
Frequently Asked Questions
A speed converter expresses the same motion in a different unit. It multiplies your value by a fixed factor, so nothing physical changes — only the label. This tool converts km/h, mph, m/s, ft/s, knots, cm/s, km/s, Mach and the speed of light at the same time, so 100 km/h appears as 62.137 mph, 27.778 m/s and 53.996 knots in one view.
Divide by 1.609344, the exact number of kilometres in a statute mile. 100 km/h ÷ 1.609344 = 62.137 mph, 50 km/h = 31.07 mph and 130 km/h = 80.78 mph. In your head, multiply by 5 and divide by 8: 100 → 500 ÷ 8 = 62.5 mph, roughly 0.6% high and close enough to read a speed limit sign.
Convert speed through exact m/s factors: 1 mph = 1.609344 km/h, 36 km/h = 10 m/s, 1 knot = 1852/3600 m/s. Mach uses a fixed approximate 340.294 m/s for dry air near 15°C; the atmospheric reference table is illustrative, not an adjustable model. Pace is distance divided by speed, rounded once to seconds: 12 km/h gives 5:00/km and 8:03/mile. Pace is undefined at zero and only displayed for 0.1 < km/h < 500. Road and vehicle examples are illustrative, not current law or attainable-speed claims.
Divide by 3.6. One hour is 3,600 seconds and one kilometre is 1,000 metres, so 1 km/h = 1000/3600 = 0.277778 m/s. That makes 36 km/h exactly 10 m/s, 90 km/h exactly 25 m/s and 100 km/h 27.778 m/s. Going the other way, multiply m/s by 3.6: a 10.44 m/s sprint average is 37.58 km/h.
A knot is one nautical mile per hour, and the nautical mile is defined as exactly 1,852 metres — about one minute of latitude. That keeps chart work simple: 10 knots for six hours covers 60 nautical miles, which is one degree of latitude. One knot equals 1.852 km/h, 1.15078 mph or 0.514444 m/s.
Convert speed through exact m/s factors: 1 mph = 1.609344 km/h, 36 km/h = 10 m/s, 1 knot = 1852/3600 m/s. Mach uses a fixed approximate 340.294 m/s for dry air near 15°C; the atmospheric reference table is illustrative, not an adjustable model. Pace is distance divided by speed, rounded once to seconds: 12 km/h gives 5:00/km and 8:03/mile. Pace is undefined at zero and only displayed for 0.1 < km/h < 500. Road and vehicle examples are illustrative, not current law or attainable-speed claims.
Speed = distance ÷ time, and the units come along for the ride: 400 m in 50 s is 8 m/s, 240 km in 3 h is 80 km/h. Convert afterwards with a single factor — 8 m/s × 3.6 = 28.8 km/h. Average speed is total distance over total time, never the average of the individual speeds.
Convert speed through exact m/s factors: 1 mph = 1.609344 km/h, 36 km/h = 10 m/s, 1 knot = 1852/3600 m/s. Mach uses a fixed approximate 340.294 m/s for dry air near 15°C; the atmospheric reference table is illustrative, not an adjustable model. Pace is distance divided by speed, rounded once to seconds: 12 km/h gives 5:00/km and 8:03/mile. Pace is undefined at zero and only displayed for 0.1 < km/h < 500. Road and vehicle examples are illustrative, not current law or attainable-speed claims.
Convert speed through exact m/s factors: 1 mph = 1.609344 km/h, 36 km/h = 10 m/s, 1 knot = 1852/3600 m/s. Mach uses a fixed approximate 340.294 m/s for dry air near 15°C; the atmospheric reference table is illustrative, not an adjustable model. Pace is distance divided by speed, rounded once to seconds: 12 km/h gives 5:00/km and 8:03/mile. Pace is undefined at zero and only displayed for 0.1 < km/h < 500. Road and vehicle examples are illustrative, not current law or attainable-speed claims.
Batch: Auto uses the locale decimal convention with dot fallback; List splits commas/whitespace and uses dot decimals. Dot supports 1,234.5; Comma supports 1.234,5 with complete three-digit grouping only. Newline, semicolon and tab separate entries. Text cap 65536 UTF-16 units; candidate cap 300 speed / 500 volume includes invalid entries. Invalid/excess entries are omitted from exports with counts; no valid rows means no export.
Convert speed through exact m/s factors: 1 mph = 1.609344 km/h, 36 km/h = 10 m/s, 1 knot = 1852/3600 m/s. Mach uses a fixed approximate 340.294 m/s for dry air near 15°C; the atmospheric reference table is illustrative, not an adjustable model.
Batch: Auto uses the locale decimal convention with dot fallback; List splits commas/whitespace and uses dot decimals. Dot supports 1,234.5; Comma supports 1.234,5 with complete three-digit grouping only. Newline, semicolon and tab separate entries. Text cap 65536 UTF-16 units; candidate cap 300 speed / 500 volume includes invalid entries. Invalid/excess entries are omitted from exports with counts; no valid rows means no export.