Speed is distance divided by time, and because both halves of that ratio come in several units, there are a lot of ways to express it. Road signs use miles per hour in the US and kilometers per hour almost everywhere else, physics problems use meters per second, pilots and sailors use knots, and runners think in minutes per mile. This converter handles all of those, and it turns any speed into a pace so you can compare a treadmill setting with a race time.
How to use the speed converter
- Enter the speed in Value.
- Choose its unit in From and the unit you want in To.
- The tape shows the result, the factor in each direction and the matching pace per mile and per kilometer.
- The table lists the speed in all 11 units, from inches per second to the speed of light.
Speed conversion formula
Every unit is stored as a number of meters per second:
Several factors are exact because the units behind them are exact. A mile is 1,609.344 m and an hour is 3,600 s, so 1 mph = 1,609.344 ÷ 3,600 = 0.44704 m/s. A km/h is 1,000 ÷ 3,600 = 1/3.6 m/s, and a knot is 1,852 ÷ 3,600 m/s. Pace is simply the reciprocal of speed:
Worked example: highway speed
A rental car’s speedometer reads only km/h, and the posted limit is 65 mph:
65 mph × 1.609344 = 104.61 km/h
In meters per second: 65 × 0.44704 = 29.06 m/s, so the car covers a mile in 1,609.344 ÷ 29.0576 ≈ 55 seconds.
For a runner, a treadmill set to 6 mph gives a pace of exactly 10:00 per mile, which is 6:13 per kilometer.
Common speed conversions
| From | To | Multiply by |
|---|---|---|
| mph | km/h | 1.609344 (exact) |
| km/h | mph | 0.6213712 |
| mph | m/s | 0.44704 (exact) |
| m/s | km/h | 3.6 (exact) |
| m/s | mph | 2.2369363 |
| knots | km/h | 1.852 (exact) |
| knots | mph | 1.1507794 |
| ft/s | mph | 0.6818182 (15/22) |
| mph | ft/s | 1.4666667 (22/15) |
A handy shortcut: 60 mph is exactly 88 feet per second, the figure driving instructors use to explain stopping distances.
Speeds for reference
| Situation | mph | km/h | m/s |
|---|---|---|---|
| Brisk walk | 3.5 | 5.6 | 1.6 |
| 10:00-per-mile run | 6 | 9.7 | 2.7 |
| US interstate limit (typical) | 65–70 | 105–113 | 29–31 |
| Commercial jet cruise | ~560 | ~900 | ~250 |
| Speed of sound, sea level | 761 | 1,225 | 340.3 |
Choosing the right unit
- m/s is the SI unit and the natural choice for physics, wind speed in science and engineering calculations.
- km/h and mph suit vehicles and everyday travel.
- Knots are standard in aviation, marine navigation and weather reports for wind at sea.
- Mach expresses speed relative to the local speed of sound. This converter uses the sea-level standard value of 340.29 m/s; at altitude, where the air is colder, Mach 1 is slower.
- Pace (time per distance) is what runners and walkers use; it gets smaller as speed increases.
To solve for speed, distance or time from the other two, try the speed, distance and time calculator. For race planning with splits, use the running pace calculator. Quick single-direction charts are available for mph to km/h and km/h to mph.
Frequently asked questions
How do I convert mph to km/h?
Multiply miles per hour by 1.609344, the exact number of kilometers in a mile. 65 mph × 1.609344 = 104.6 km/h. To go from km/h to mph, multiply by about 0.621371.
How fast is a knot?
One knot is one nautical mile per hour: exactly 1.852 km/h, or about 1.151 mph. Ships and aircraft use knots because a nautical mile corresponds to one minute of latitude.
How do I convert meters per second to km/h?
Multiply by 3.6. There are 3,600 seconds in an hour and 1,000 meters in a kilometer, so 1 m/s = 3,600 m/h = 3.6 km/h. A 10 m/s wind is 36 km/h, or about 22.4 mph.
What speed is Mach 1?
Mach 1 is the speed of sound, which depends on air temperature. In the standard atmosphere at sea level (15 °C) it is about 340.3 m/s, 1,225 km/h or 761 mph. In the cold air at airliner cruising altitude it drops to roughly 660 mph.