We're afraid this has an 'it depends' answer.
It depends on how old you are, when you want to retire and what you consider to be a decent pension.
It depends on whether you have any pension already, and whether you have been automatically enrolled or have the option of joining a scheme that your employer will also pay into.
Another way of answering this question is to say that many experts agree that to retire with a pension of half your salary you need to start saving in your twenties and need to make contributions of about 15% of your income during the whole of your working life.
If you start later, you need to save more.
Few can probably afford all of this, unless they can call on a substantial part of this from their employer. It's one reason why many people are talking of a pensions crisis and why a system of automatic enrolment into workplace pensions has now been set up.