# Tutorial: calculating the average speed – this is how it’s done!

"It’s 106 miles to Chicago, we have a full tank of gas. ". If the Blues Brothers in the movie of the same name need 50 minutes for these 106 miles, then they drive too fast. But how to calculate the average speed?

## Calculate average speed: The formula

The term average speed already assumes that you have different speeds during your drive. Maybe you drive 50 km/h in the city in the beginning or even partly only 30 km/h. Later – on the highway – you can sometimes accelerate up to 180 km/h. If you want to make it complicated, then subtract all legs at the respective pace – but that’s unnecessary!

alt="Some on-board computers can even calculate and display the average speed" width="570" height="" /> Some on-board computers can even calculate and display average speed

The average speed is the result of a division. It is the quotient of distance and time. Or simply expressed:

If you divide the distance traveled by the time taken, you get the average speed.

So if it takes one hour to travel 100 kilometers, then the average speed is 100 km/h. And it doesn’t matter if you drove only 50 in the beginning and later on 150. In the end, it’s the ratio between distance and time that counts. If you need for 100 kilometers only 30 minutes, then the calculation is

100 km / 0.5 h. = 200 km/h

In general, we can calculate the average speed by applying the following formula:

alt="diameter-calculate-formula" width="174" height="" /> Diameter Calculating Formula

This means: Average speed is equal to distance divided by time.

## Calculate average speed: When it has to be very precise

When calculating the average speed, you often take the simplest formula. One divides driven distance by driving time. But if you took a half hour break during a 5 hour drive, actually the calculated average speed is not correct. The actual travel time was not 5 hours, but only 4.5 hours. The 5 hours is only the travel duration – not the travel time.

So if you want to know exactly, in such a situation you have to stop the breaks already during the trip and subtract them from the travel duration afterwards. This results in the correct driving time, by which the distance is finally divided.

### Another small explanation for the introduction

If the Blues Brothers drove the 106 miles in 50 minutes, then they were definitely too fast. The most allowed speed limit in the USA is between 70 and 80 miles per hour.

If they rode the distance in 50 minutes, the calculation is

V = 106 miles / 0.8333 hours (since 50 minutes is about 0.83-infinite hours).)

So we can then calculate an average speed for the distance, which is about 127.7 m/h. That’s over 205 km/h – and even the Blues-Mobile can’t do that!

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