The short answer is: no. You don't have to walk 10,000 steps every single day, either if you're doing it for weight loss or health benefits.
However, there's evidence suggesting that setting your goal at 7,500-8,000 steps is a good idea. This level reduces your cardiovascular disease risk, and your overall mortality.
If you are trying to lose those extra pounds by walking, 10k steps or more might be a good idea. Keep an eye on your step counter if you sit a lot on a daily basis. Also, it is better to move few times a day for a shorter time than do the one long 15k steps walk in the morning and spend the rest of the day laying in bed! Read more