If walking is your only form of movement during the day and you basically have a desk job that keeps you seated for most of the day, I would recommend at least 30 minutes a day of brisk walking to get your heart pumping and circulation flowing through your body. If you start walking more, you will notice that your body will crave more movement when you are seated for long periods of time, so try to incorporate short walks throughout your day if you can.
There are a couple of factors that determine how far you should walk every day. One is whether or not you want to lose weight or maintain your current weight. The other factors are how much you weigh and your pace. Walking burns calories so depending on whether you want to lose or maintain your weight will determine how many calories you need to burn and then the distance is determined by your weight and pace.
You don't need to measure the distance as much as the time and heart rate. Everyone walks at a different speed and the size of their steps is different. It is recommended that you walk or do some other form of cardio for at least 30 minutes a day.
IF you want to lose weight by exercise or walking you need at least 30 minutes unless your over weight then its 15-20 minutes per day then work into 30 this was recomended by a doctor !!!!!!!!!!!!!!!!!