There are many different ways to identify the cost for a budget and gradually build up that budget. One of these is to start with your outputs. My example here is going to be to come up with a training budget.

I know what my desired output's going to be. It's going to be a figure a cost for that training budget. I now need to work out what calculations I need to do in order to come up with that training budget. I think four major headings here are going to be to calculate the teaching cost, to calculate the training materials cost, such as books to calculate the travel and accommodation cost for students who need to travel and need to stay overnight, maybe for a number of days or weeks, and then the venue cost, renting the space, the cost of meals, maybe renting laptops in the venue, IT support, internet access, et cetera. Lots of these mentioned are assumptions, and I want to try and detail out my assumptions for just one of these being the teaching cost. My teaching cost will be made up of a number of items. My first assumption will be the instructor cost per day, but we now need more assumptions to go with that. If I've only got the instructor cost per day, I now need to make an assumption for the number of days of training that are going to be delivered. On top of that, I need to know how many classrooms are required. That will then require us to know how many participants are going to be on the course and how many participants can fit in each room. We've also got the teaching assistant cost per day, and that will be impacted by the same things, the number of days and the number of classrooms. If we can lay out all of our assumptions individually, then we can bring them all together into calculations and then bring all of our calculations together into our budget.