How long do you have to walk to burn 500 calories without dieting?

It depends, from what I've read, on whether it's a slow, leisurely walk or a faster, brisk walk. My doctor told me to aim for 1 Kilometer per 500 calories I wanted to burn off, even though that means that eventually I'm going to burn off more than the 500 calories, since as I go, I'll get better and faster at walking that distance...But in my mind I'll still be thinking 500 calories.

Another suggestion was that I walk for basically no less than twenty minutes, and that would count for my 1 kilometer, and that whether it was a slow walk or a fast walk, the 20 minute mark was good to aim for.

So I guess, about 20 minutes, or 1 kilometer ought to do it, I think.