Ten thousand steps was a marketing figure from a Japanese pedometer in the 1960s. It was never a research finding. The real numbers are more encouraging than that.
What the evidence shows
Large studies tracking step counts against death rates find a clear dose-response relationship that flattens out well before ten thousand. Meaningful reductions in mortality appear from around four thousand steps a day, with most of the available benefit captured somewhere between seven and eight thousand. Beyond that the curve keeps improving slightly but the returns get small.
The pattern holds across age groups, though the point at which the curve flattens tends to be lower in older adults.
How much difference it makes
The largest gains belong to the people currently moving least. Going from two thousand steps a day to five thousand is a bigger change in your risk than going from eight thousand to twelve. If you are sedentary, you have the most to gain and the least distance to travel.
Intensity adds something on top. A brisk walk where you are slightly breathless does more than the same number of steps taken slowly.
What to do
Find your current average over a week before setting a target. Most people guess badly. Then add roughly a thousand steps a day and hold it for a fortnight before adding more.
Attach walking to something that already happens rather than treating it as a separate task. Getting off a stop early, a walk after dinner, or taking calls on your feet all work better than an appointment with yourself that you can cancel.
Cautions
If you have foot problems, particularly with diabetes, check your feet regularly when you increase walking. Neuropathy means an injury can go unnoticed until it is serious.
When to see a doctor
Calf pain that comes on reliably after a certain distance and settles with rest is worth mentioning to your doctor rather than pushing through.