Speed Calculator
Calculate speed, distance, and time using the fundamental physics formula
Speed, Distance & Time Calculator
What do you want to calculate?
Calculation Results
Speed in Different Units
Formula Used
Speed References
Quick Conversions
km/h to mph
Multiply by 0.621
mph to km/h
Multiply by 1.609
m/s to km/h
Multiply by 3.6
knots to km/h
Multiply by 1.852
Understanding Speed
What is Speed?
Speed is a measure of how quickly something moves from one place to another. It's the distance traveled divided by the time taken to travel that distance.
The Speed Formula
Speed = Distance ÷ Time
Distance = Speed × Time
Time = Distance ÷ Speed
Types of Speed
- •Average Speed: Total distance ÷ total time
- •Instantaneous Speed: Speed at a specific moment
- •Constant Speed: Unchanging speed over time
Speed vs Velocity
Speed (Scalar)
Speed is a scalar quantity - it only has magnitude (how fast). Example: "50 km/h"
Velocity (Vector)
Velocity is a vector quantity - it has both magnitude and direction. Example: "50 km/h northeast"
Real-World Example
A car driving in a circle at constant speed has changing velocity (due to changing direction) but constant speed.
Frequently Asked Questions
What's the most economical driving speed?
Most vehicles achieve optimal fuel efficiency at around 80 km/h (50 mph). Driving at constant speeds and using cruise control can improve fuel economy significantly.
How do I convert between speed units?
Common conversions: 1 m/s = 3.6 km/h = 2.237 mph. To convert mph to km/h, multiply by 1.609. To convert km/h to mph, multiply by 0.621.
What's the difference between average and instantaneous speed?
Average speed is total distance divided by total time. Instantaneous speed is your speed at any given moment (what your speedometer shows). They can be very different!