Going 60 km at 40 km/h and back at 60 km/h averages 48 km/h, not 50. Enter each leg's distance and speed to get the correct average speed.
Enter each leg's distance.
Enter the speed on each leg.
Read the average speed.
Average speed: Total distance ÷ total time
Equal distances: 2xy ÷ (x + y)
Average speed is total distance divided by total time. The calculator takes a journey split into legs, each with its own distance and speed, works out the time for each leg, and gives the true average speed for the whole trip.
The idea sounds obvious, but many people average the speeds directly. Drive 60 km at 40 km/h and 60 km back at 60 km/h and the answer is 48 km/h, not 50. This trap appears in almost every aptitude test, and matters in real life when estimating travel time on highways with slow ghat sections or city traffic.
Enter distances and speeds in the same order and the same units. The calculator shows each leg's time and the totals.
1. List each leg's distance d and speed v.
2. Find each leg's time t = d ÷ v.
3. Add all distances to get total distance.
4. Add all times to get total time.
5. Average speed = total distance ÷ total time.
6. For two equal distances at speeds x and y, use the shortcut 2xy ÷ (x + y).
Average speed is a weighted average of the leg speeds, weighted by time spent on each. Slow legs take longer, so they carry more weight, pulling the average below the simple mean. If equal time is spent at each speed, the time weights are equal and the simple mean is correct. If equal distance is covered at each speed, the answer is the harmonic mean. For n equal distances, the average speed is n ÷ (1/v₁ + 1/v₂ + ... + 1/vₙ).
Suppose you need to average 60 km/h over a 120 km round trip and you drove the first 60 km at 30 km/h. That took 2 hours, which is already the whole time budget for 120 km at 60 km/h. No speed on the return can rescue it. This shows that time lost on slow sections cannot be fully recovered by speeding later, which is useful for trip planning and exam trick questions.
In physics, average velocity is displacement divided by time, and it has a direction. For a round trip that ends where it started, displacement is zero, so average velocity is zero even though average speed is not. Everyday travel and aptitude questions mean average speed. Stops count as time, so a halt of 30 minutes during a journey lowers the average speed even though distance does not change.
Shalini drives from Mumbai toward Lonavala: 120 km of expressway at 60 km/h, 80 km of mixed road at 40 km/h, and a final 40 km through ghat traffic at 20 km/h.
Time for each leg = distance ÷ speed: 120 ÷ 60 = 2 h 80 ÷ 40 = 2 h 40 ÷ 20 = 2 h
Total distance and time: 120 + 80 + 40 = 240 km 2 + 2 + 2 = 6 h
Average speed: 240 ÷ 6 = 40 km/h
Answer: Average speed 40 km/h; Total distance 240 km; Total time 6 hours
Averaging the speeds directly when distances, not times, are equal.
Leaving out rest stops when computing the actual average for a completed trip.
Mixing kilometres with metres, or hours with minutes, across legs.
Assuming a fast later leg can make up any amount of time lost earlier.
Planning road trip durations with sections at different speeds.
Solving average speed questions in aptitude exams.
Analysing running or cycling splits over a route.
Checking delivery or logistics timings across mixed road types.
When is the simple average correct?
When equal time, not equal distance, is spent at each speed.
Can I use metres and seconds?
Yes, as long as both lists use matching units.