Speed Distance Time Calculator
The speed-distance-time calculator solves for any one of three variables when the other two are known. Enter distance and time to find speed, distance and speed to find time, or speed and time to find distance. All three results are shown simultaneously.
Advertisement
Calculator
See your Speed Distance Time Calculator results
Enter your email to unlock results — free forever.
No spam, ever. Unsubscribe at any time.
Advertisement
Formula
v = d / t
Speed (v) equals distance (d) divided by time (t). Rearranged: distance = speed × time, and time = distance ÷ speed. This is the foundational equation of kinematics and applies to any object moving at constant speed.
How to use the Speed Distance Time Calculator
- 1
Enter your distance
Value should be in m.
- 2
Enter your time
Value should be in s.
- 3
Enter your speed (leave 0 to calculate)
Value should be in m/s.
- 4
Read your results instantly
Results update in real time as you type.
Advertisement
Understanding speed, distance, and time
Speed, distance, and time are the three fundamental quantities of motion. Speed is how fast an object moves — the distance covered per unit of time. Distance is the total path length traveled. Time is how long the journey takes. Knowing any two allows you to calculate the third.
In everyday life, these calculations are everywhere: a car traveling at 60 mph for 2 hours covers 120 miles. A runner completing a 10 km race in 50 minutes averaged 12 km/h. A signal traveling at the speed of light (300,000 km/s) takes about 1.3 seconds to reach the Moon. The formula v = d/t is one of the first equations in physics and remains one of the most used.
Note that this calculator assumes constant speed. Real-world motion involves acceleration and deceleration — for those cases, use the Acceleration Calculator.
Unit conversions to watch out for
The formula v = d/t only works when distance and time use consistent units. If distance is in meters and time is in seconds, speed comes out in m/s. If distance is in kilometers and time is in hours, speed is in km/h. Mixing units — like kilometers and seconds — produces a numerically correct but unitfully wrong answer.
Common conversions: 1 km/h = 0.2778 m/s. 1 mph = 1.609 km/h = 0.4470 m/s. The speed of sound in air at sea level is about 343 m/s (1,235 km/h). The speed of light is 299,792,458 m/s. When solving problems, always state your units and convert everything to a consistent system before plugging in numbers.
Advertisement
Average speed vs. instantaneous speed
This calculator computes average speed — the total distance divided by total time. Instantaneous speed is the speed at any single moment, like what a speedometer reads. For trips with varying speed (city driving, hiking with rest breaks), average speed smooths over all the variation.
A common mistake: averaging two speeds without accounting for time. If you drive 60 mph for one hour, then 30 mph for one hour, your average speed is (60+30)/2 = 45 mph. But if you drive 60 mph for one hour and 30 mph for two hours, the average is 120 miles / 3 hours = 40 mph. Always use total distance divided by total time for accurate averages.
Tips & Insights
Use consistent units
Before calculating, convert all values to the same unit system (SI: meters and seconds, or imperial: miles and hours). Mixing km with seconds or miles with minutes leads to wrong answers.
Speed of light check
Light travels 300,000 km/s. If your calculated speed approaches or exceeds this, you've likely made a unit error — no physical object with mass can reach the speed of light.
For trips with stops, use net travel time
If you want average driving speed, use only the time the vehicle was moving. Including stopped time (traffic, rest stops) gives average journey speed, which is always lower than average driving speed.
Worked Examples
100m sprint
Speed = 100 ÷ 9.8 ≈ 10.2 m/s (about 36.7 km/h). World-class sprinters average over 10 m/s across the full 100m.
Highway driving
150 km in 1.5 hours: speed = 150,000 m ÷ 5,400 s ≈ 27.8 m/s = 100 km/h.
Advertisement
Frequently Asked Questions
What is the speed distance time formula?
Speed = Distance ÷ Time. Rearranged: Distance = Speed × Time, and Time = Distance ÷ Speed.
How do I convert m/s to km/h?
Multiply m/s by 3.6. For example, 10 m/s × 3.6 = 36 km/h.
What is the difference between speed and velocity?
Speed is a scalar — just how fast. Velocity is a vector — how fast and in what direction. This calculator computes speed (magnitude only).
Can speed be negative?
In everyday use, no. Speed is the magnitude of velocity. Velocity can be negative (indicating direction), but speed is always zero or positive.
What units should I use?
Use any consistent units. SI units (meters, seconds) give m/s. For km/h, use kilometers and hours. For mph, use miles and hours.
Advertisement