Speed Distance Time Guide: Formulas & Examples
Speed, distance, and time are three of the most practical mathematical quantities in everyday life — from road trips to physics problems. Here's everything you need.
The Three Formulas
Speed Unit Conversions
| From | To m/s | To km/h | To mph |
|---|---|---|---|
| 1 m/s | = 1 | = 3.6 | = 2.237 |
| 1 km/h | = 0.278 | = 1 | = 0.621 |
| 1 mph | = 0.447 | = 1.609 | = 1 |
Frequently Asked Questions
What is the speed, distance, time triangle?
The SDT triangle is a memory aid: put D (distance) on top, S (speed) and T (time) on the bottom. Cover the value you want to find: D = S × T; S = D ÷ T; T = D ÷ S. It applies to any consistent set of units.
How do I convert speed units?
1 km/h = 1000 ÷ 3600 = 5/18 m/s ≈ 0.278 m/s. 1 m/s = 3.6 km/h. 1 mile/h (mph) = 1.609 km/h. For the speed formula, ensure distance and time use matching units (km with hours, m with seconds, etc.).
What is average speed?
Average speed = Total Distance ÷ Total Time. Not the average of two speeds. If you drive 60 km/h for 1 hour and 100 km/h for 1 hour: total distance = 160 km, total time = 2 hours, average speed = 80 km/h (which happens to equal the arithmetic mean here only because times are equal).
What is relative speed?
When two objects move in the same direction, their relative speed = difference of speeds. When moving toward each other (opposite directions), relative speed = sum of speeds. Used to calculate time to meet or overtake.
How do I calculate travel time for a journey?
T = Distance ÷ Speed. A 450 km journey at 90 km/h takes 450 ÷ 90 = 5 hours. Factor in breaks, traffic, and speed limits for real-world estimates. Converting to hours and minutes: 0.5 hours = 30 minutes.
Related Calculators
Solve Speed, Distance, Time Problems
Enter any two values to instantly find the third — speed, distance, or time.
Open Speed Calculator