I heard this commercial on the radio the other morning about the three-day walk to raise money for breast cancer research.  The guy in the commercial said something to the effect that he’d walk a million miles to make breast cancer go away.  It’s certainly a worthy project, and I don’t mean to demean their effort.  However, the math geek in the back of my brain started grumbling about it, to the point where I couldn’t help but grab the calculator and do the calculations.  My initial impression was that it would be impossible to do this as it would take longer than the human lifespan to walk one million miles.

In order to determine that, though, we have to establish a few assumptions to feed into the calculations.  First, what is the average walking speed for an adult?  I seem to recall reading somewhere that it ranged from two to four miles per hour.  I know that from my morning dog walks that I have to keep up a fairly decent pace to maintain an average of three miles per hour (although this average includes doggie sniff/pee/poop activities, which means the actual speed is likely higher).  But for the sake of this calculation I will use three miles per hour. 

Using just the average speed would not give us a very accurate idea of how long it would take to walk one million miles, though, since humans are not capable of walking that far without stopping for food, water, and sleep.  Let’s assume that the person treats this like a day job and spends eight hours per day walking.  At this point we face the choice of whether this person also stops for weekends or goes every day.  To simplify this a bit, we will assume that this person walks every day without any days off.  Further, we will assume that a year is 365 days (i.e. we won’t worry about leap years/days).

So, at three miles per hour, one million miles would take approximately 333333.33 hours (damn repeating decimal…  should have chosen 4 mph I guess).  If we divide that by 8hr/day we get approximately 41666.67 days.  At 365 days/year that would come to approximately 114.16 years. 

Just for kicks, here are the results for some other speeds (assuming 8 hours per day and 365 days per year):

After analyzing this one to death, I think I can say that my original suspicion was correct.  You can’t walk one million miles, at least not at a sustainable pace during a normal human lifespan.