Speed, Distance, and Time Formula Explained
Speed, distance, and time are linked by one of the simplest and most useful formulas in all of maths: Distance = Speed × Time. Rearrange it and you can solve for any of the three variables. This relationship shows up everywhere — road trips, running pace, physics homework, and project planning.
This guide covers all three rearrangements, works through real examples, and highlights the unit-conversion traps that trip people up most often.
✨Key takeaways
- Distance = Speed × Time. Speed = Distance ÷ Time. Time = Distance ÷ Speed.
- Units must match: if speed is in km/h, distance must be in km and time in hours.
- For minutes-per-mile pace: time (min) = 60 ÷ speed (mph).
- The [Speed-Distance-Time Calculator](/calculators/speed-distance-time-calculator) solves for any unknown automatically.
The three rearrangements
1. Distance = Speed × Time. "How far will I get?"
2. Speed = Distance ÷ Time. "How fast was I going?"
3. Time = Distance ÷ Speed. "How long will it take?"
These three are the same equation, just rearranged. The "triangle trick" works: cover the variable you want to find, and the remaining two show you the operation.
Example 1: A road trip
You are driving 280 miles at an average speed of 65 mph. How long will it take?
Time = Distance ÷ Speed = 280 ÷ 65 = 4.31 hours = 4 hours 18 minutes.
Add 15 minutes for a fuel stop and you should plan for about 4.5 hours door to door.
Example 2: A running pace
You ran 5 km in 27 minutes. What was your pace and speed?
Speed = 5 ÷ (27/60) = 5 ÷ 0.45 = 11.11 km/h.
Pace = 27 ÷ 5 = 5.4 min/km = 5 minutes 24 seconds per kilometre. In miles: 5.4 × 1.609 ≈ 8:41 min/mile.
Example 3: A physics problem
A car accelerates uniformly from rest to 20 m/s over 200 metres. What is the average speed and time taken?
Average speed = (0 + 20) / 2 = 10 m/s (for uniform acceleration, average speed = (initial + final) / 2).
Time = Distance ÷ Average Speed = 200 ÷ 10 = 20 seconds.
The unit trap
The most common mistake: mixing units. If speed is in km/h, distance must be in km and time in hours — not minutes.
A 45-minute drive at 80 km/h: Distance = 80 × (45/60) = 80 × 0.75 = 60 km. NOT 80 × 45 = 3,600.
When in doubt, convert everything to the base units first (km and hours, or miles and hours), compute, then convert the answer back.
The Unit Converter handles km/mph/m/s conversions if you need to switch systems mid-problem.
Try the calculators referenced in this guide
Put the maths into practice — every calculator is free and runs entirely in your browser.
Frequently Asked Questions
How do I convert between km/h and m/s?
Divide km/h by 3.6 to get m/s. Multiply m/s by 3.6 to get km/h. So 100 km/h = 27.78 m/s.
What if the speed changes during the trip?
Use average speed = total distance ÷ total time. If you drove 100 km at 80 km/h and then 100 km at 120 km/h, total time = 1.25 + 0.833 = 2.083 hours. Average speed = 200 ÷ 2.083 = 96 km/h — not 100.
Why is the average of two speeds not the average speed?
Because you spend more time at the slower speed. At 60 km/h for 100 km = 1.667 hours. At 120 km/h for 100 km = 0.833 hours. Average speed = 200 / 2.5 = 80 km/h, not 90.
The Precision Calculator Editorial Team
The editorial team at Get Precision Calculator writes practical, formula-driven guides that explain the maths behind every calculator on this site. All content is reviewed for accuracy before publishing.
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