Completion time on a company where the supervisors don't know programming [duplicate]

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• Is there a way to combat Sales perpetually overcommitting? [closed] 21 answers

We are in a small company with around 10 developers. I am the team leader and responsible for the development process.

Supervisors and salesmen are close to us since we are a small team, but have no clue on how software is developed.

When they ask me how much time I want for a change (bugfixes/features) in a product, my response is 'let me calculate it'. After giving them the schedule, they start by saying OK you can do it in XX time which differs a lot from my plan. We are using a model close to Agile basic principles and have circles per week or per three days.

Of course I argue and say that this cannot be done. They seem to have no idea on the effort we are doing. They do not want to see WHY my schedule is for that amount of time.

I know this behavior is stupid, but how can I make them see the problem?