km/h, mph, knots and metres per second
Convert speeds between kilometres per hour, miles per hour, knots, feet per second and the SI unit every physics formula expects, metres per second. Useful for reading a foreign speed limit, a marine or aviation forecast, or a homework question that quietly changed units halfway through. Updates as you type; nothing is uploaded or saved.
- Nothing is uploaded or saved
- Works offline
Speed converter
Kilometre per hour to Mile per hour
62.1371192237mph
100 km/h = 62.1371192237 mph
1 km/h = 0.621371192237 mph
1 mph = 1.609344 km/h
The same amount in every unit
Common speed conversions
Every figure below is produced by the same conversion code as the calculator above, so the two can never disagree.
Kilometres per hour to mph
| Kilometre per hour (km/h) | Mile per hour (mph) | Metre per second (m/s) |
|---|---|---|
| 10 | 6.21371192237 | 2.77777777778 |
| 20 | 12.4274238447 | 5.55555555556 |
| 30 | 18.6411357671 | 8.33333333333 |
| 40 | 24.8548476895 | 11.1111111111 |
| 50 | 31.0685596119 | 13.8888888889 |
| 60 | 37.2822715342 | 16.6666666667 |
| 70 | 43.4959834566 | 19.4444444444 |
| 80 | 49.709695379 | 22.2222222222 |
| 90 | 55.9234073014 | 25 |
| 100 | 62.1371192237 | 27.7777777778 |
| 110 | 68.3508311461 | 30.5555555556 |
| 120 | 74.5645430685 | 33.3333333333 |
| 130 | 80.7782549909 | 36.1111111111 |
| 140 | 86.9919669132 | 38.8888888889 |
Miles per hour to km/h
| Mile per hour (mph) | Kilometre per hour (km/h) | Metre per second (m/s) |
|---|---|---|
| 5 | 8.04672 | 2.2352 |
| 10 | 16.09344 | 4.4704 |
| 20 | 32.18688 | 8.9408 |
| 25 | 40.2336 | 11.176 |
| 30 | 48.28032 | 13.4112 |
| 40 | 64.37376 | 17.8816 |
| 50 | 80.4672 | 22.352 |
| 55 | 88.51392 | 24.5872 |
| 60 | 96.56064 | 26.8224 |
| 65 | 104.60736 | 29.0576 |
| 70 | 112.65408 | 31.2928 |
| 75 | 120.7008 | 33.528 |
| 80 | 128.74752 | 35.7632 |
Knots to km/h and mph
| Knot (kn) | Kilometre per hour (km/h) | Mile per hour (mph) |
|---|---|---|
| 1 | 1.852 | 1.15077944802 |
| 5 | 9.26 | 5.75389724012 |
| 10 | 18.52 | 11.5077944802 |
| 15 | 27.78 | 17.2616917204 |
| 20 | 37.04 | 23.0155889605 |
| 25 | 46.3 | 28.7694862006 |
| 30 | 55.56 | 34.5233834407 |
| 40 | 74.08 | 46.0311779209 |
| 50 | 92.6 | 57.5389724012 |
| 60 | 111.12 | 69.0467668814 |
| 80 | 148.16 | 92.0623558419 |
| 100 | 185.2 | 115.077944802 |
A knot is one nautical mile per hour — exactly 1.852 km/h. “Knots per hour” would be an acceleration.
Metres per second to km/h
| Metre per second (m/s) | Kilometre per hour (km/h) | Mile per hour (mph) |
|---|---|---|
| 1 | 3.6 | 2.23693629205 |
| 2 | 7.2 | 4.47387258411 |
| 3 | 10.8 | 6.71080887616 |
| 4 | 14.4 | 8.94774516822 |
| 5 | 18 | 11.1846814603 |
| 6 | 21.6 | 13.4216177523 |
| 8 | 28.8 | 17.8954903364 |
| 10 | 36 | 22.3693629205 |
| 15 | 54 | 33.5540443808 |
| 20 | 72 | 44.7387258411 |
| 25 | 90 | 55.9234073014 |
| 30 | 108 | 67.1080887616 |
How it works
- 1
Type the speed
Enter the number and pick its unit. The result recalculates on every keystroke, and the panel beside it shows the same speed in all five units at once — handy when a forecast gives wind in knots and a limit sign gives km/h.
- 2
Pick what you want it in
Metric, imperial, marine and scientific units sit in the same list. Going from knots to km/h is the same two taps as km/h to mph.
- 3
Swap the direction
The swap button exchanges the units and keeps the number you typed, so reading a speed both ways takes one tap rather than retyping.
- 4
Check it against the tables
km/h to mph across the range of ordinary speed limits, mph back the other way, and knots to both. Generated from the same conversion code as the calculator, so they cannot disagree with it.
Frequently asked questions
How do I convert km/h to mph in my head?
Multiply by 0.6214, or for a road-sign estimate halve it and add a tenth of the original: 100 km/h halves to 50, plus 10 is 60, against an exact 62.14 mph. Going the other way, multiply by 1.6 — 60 mph × 1.6 is 96, against an exact 96.56 km/h. Both are close enough to know whether you are speeding and not close enough to argue with.
What is a knot, and why is it used at sea?
A knot is one nautical mile per hour, which is exactly 1.852 km/h. It is used because a nautical mile is one minute of latitude, so a navigator working on a paper chart can measure distance against the latitude scale in the margin and get speed, distance and position without converting anything. The name is literal: speed used to be measured by streaming a knotted line off the stern and counting how many knots ran out in a fixed time. Aviation kept knots because it kept the same charts.
Is “knots per hour” wrong?
Yes. A knot already means one nautical mile per hour, so “knots per hour” describes a change in speed — an acceleration — rather than a speed. The correct phrase is simply “twenty knots”.
Why is Mach not in the list?
Because Mach is not a speed. It is a ratio against the local speed of sound, and the speed of sound changes with air temperature: it is roughly 1,225 km/h at sea level on a standard day and roughly 1,062 km/h at the altitude airliners cruise at. A single fixed conversion would therefore be wrong nearly everywhere it was used, and it would look authoritative while being wrong. It is left out rather than printed with a footnote nobody reads.
Why does metres per second matter if nobody drives in it?
Because it is the SI unit, and every physics formula assumes it. Feed km/h into a kinetic energy or momentum calculation and the answer is out by a factor of 3.6 — or 12.96 once it is squared. The conversion is clean in both directions: 1 m/s is exactly 3.6 km/h, so 10 m/s is 36 km/h.
Can it convert running pace?
Not directly, because pace is upside down. Speed is distance divided by time; pace is time divided by distance, so minutes per kilometre is the reciprocal rather than another unit. Convert it first by dividing 60 by the pace in minutes: a 5-minute kilometre is 60 ÷ 5 = 12 km/h, which this page then turns into 7.46 mph. A 4-minute kilometre is 15 km/h.
Is anything I type uploaded or saved?
No. It is worked out in your browser, there is no server behind this site, and nothing is stored on your device.