At the beginning of each project, I set up a production sheet. It’s a pretty simple tool for keeping track of your client’s contact information, details about the project, and track the time and resources you spend on a project. When the project is finished, I add up the time I’ve spent, and use that to determine whether I have come in over / underbudget for time spent. By taking the time to track your hours and materials purchased for a project, you’ll make it easier for yourself in the future when quoting for similar projects.
Here is a free PDF template of a Time Sheet you can use to help track the time spent on your illustration / design projects.