Should adults get 10,000 steps a day?
The US Surgeon General recommends that adults get 30 minutes of activity (beyond typical daily life) on most days of the week. It takes roughly 2,000 steps to walk a mile, and two miles of brisk walking can be completed in 30 minutes (so that's 4,000 steps). Therefore, the goal of taking 10,000 steps (or about five miles total) in a day is a rough equivalent to the Surgeon General's recommendation with the assumption that an individual gets 6,000 steps over the course of their other daily activities. This is the approximate amount of daily physical activity that's been shown to reduce risk for chronic disease and an early death in large epidemiological research studies.
However, if you happen to be someone who doesn't take many steps in normal daily life - for example, working at a desk or driving a taxi - then you should modify your initial goal downward. If you normally average 3,000 steps a day, then your initial goal might be to try to reach 4,000 or 5,000 steps a day. When you've mastered that, then work up to 7,000, and eventually 10,000. One way to gradually make your way up to 10,000 steps is the 20% Boost Program: Fit Walking into Your Life.
It is also important to keep in mind that 10,000 steps may not be the optimal level for certain groups. A 2004 study published in the journal Sports Medicine entitled "How Many Steps/Day Are Enough?" suggested that, with possible individual exceptions, "10 000 steps/day may not be sustainable for some groups, including older adults and those living with chronic diseases." The article cited another study that found that one sample of healthy older adults involved in weekly exercise programs reached an average of about 6,500 steps (+/- 3,000). The article also noted that 10,000 steps may be too low of a goal for children. The authors did conclude, however, that "10,000 steps/day appears to be a reasonable estimate of daily activity for apparently healthy adults."
Individuals with health conditions or who are currently not very active should talk with their healthcare provider before starting a walking routine.
See also, "What's the recommended amount of physical activity for adults?"
