Enter distance and time to calculate speed — or flip it around and solve for distance or time instead. Choose your preferred units (km, miles, meters) and time format (hours, minutes, seconds), then get your average speed, along with the equivalent values in other common units like mph, km/h, and m/s.
Result
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Speed in km/h
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Speed in mph
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Speed in m/s
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Speed in knots
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Distance
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Time
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Speed is the rate at which an object covers distance over a given period of time. It is a scalar quantity defined as distance divided by time (s = d/t). In the SI system, speed is measured in meters per second (m/s), though kilometers per hour (km/h) and miles per hour (mph) are also commonly used in everyday contexts.
The average speed formula is: Speed = Distance ÷ Time. If you know any two of the three values — speed, distance, or time — you can calculate the third. For distance: d = s × t. For time: t = d ÷ s.
To convert km/h to mph, divide the speed in km/h by 1.60934. For example, 100 km/h ÷ 1.60934 ≈ 62.14 mph. This calculator automatically shows your result in mph, km/h, m/s, and knots simultaneously.
No. Speed is a scalar quantity — it only describes how fast an object is moving. Velocity is a vector quantity that includes both magnitude (speed) and direction. For example, 60 mph north is a velocity, while 60 mph alone is a speed.
To convert mph to a per-second figure, divide the mph value by 3600 (the number of seconds in an hour). So 60 mph = 60 ÷ 3600 ≈ 0.01667 miles per second, or equivalently about 88 feet per second.
Most vehicles achieve peak fuel efficiency between 45–65 mph (72–105 km/h). Driving above this range significantly increases aerodynamic drag and fuel consumption. Studies generally suggest around 55 mph (88 km/h) as an optimal balance between speed and fuel economy.
Common types of speed include: instantaneous speed (speed at a single moment in time), average speed (total distance divided by total time), rotational speed (revolutions per unit time), and terminal velocity (maximum speed reached when drag equals gravitational force). This calculator computes average speed.
The SI unit for speed is meters per second (m/s). However, many practical applications use kilometers per hour (km/h) for road travel, miles per hour (mph) in the US and UK, knots (kn) for maritime and aviation contexts, and feet per second (ft/s) in certain engineering fields.