Break it down with clients as much as possible, tell them how long everything will take (don't worry overestimate just to be safe), then I explain software is n

Break it down with clients as much as possible, tell them how long everything will take (don't worry overestimate just to be safe), then I explain software is not only about writing code so we have to add 20-40% for QA/itterations on top of estimated value. But the thing is, it's only to estimate, I will never bill based on these estimations, just help to plan the client.