As a PM who has often had to take developer estimates to management meetings only to have them questioned, I've found a couple of things that work:<p>1. If there's something unintuitive to a non-technical person, call that up out front as a reason for the estimate. For example, if you're estimating how long it'll take to implement a popup, but there's some piece of information displayed in the popup that you need to get from some archaic system that is held together with tape and glue, you might come up with an estimate that seems very large to someone who thinks all you're doing is implementing a popup. When this happens, it's best to call it out up front when giving the estimate, as opposed to giving a big estimate and then giving the explanation only when questioned.<p>2. On a related note, give options. This works very well with toddlers (don't tell them they have to put on pajamas, ask them if they want to put on the red ones or the blue ones) but also often with PMs and management. In the prior example, instead of saying that it's going to take three weeks, say that it's going to take three weeks, but two weeks of that is because you have to pull this one piece of information from that archaic system. If we could go without displaying that piece of information, then the estimate is a week. If we could instead display this similar piece of information that's easier to get, then the estimate is a week and a half. When you do this, you come off as thoughtful and prepared, and you put the people you're talking to in a position where they feel like they've done something by making a choice.<p>People generally question estimates because of a lack of context, so when they do so, I really encourage you to think of it not as them not trusting you, but rather as them attempting to get the context they need to understand.<p>Some people do also question estimates because they feel like it's their job to haggle developers down (these people are annoying and do not represent most PMs). Number 2 above is a good way of dealing with this - it turns it from haggling into a negotiation over scope.