Capacity Planning
Capacity planning is working out, ahead of time, how much work you can realistically take on given the people, hours, and tools you have, so you commit to what you can actually deliver rather than discovering the ceiling by overshooting it. It means knowing roughly how much effort each unit of work consumes, how much total capacity exists, and how much is already spoken for, then saying yes or no to new work against that honest picture.
For a lean founder this is the antidote to the boom-bust trap of solo and small-team work: overselling, drowning, delivering late, then under-selling while you recover. Even a rough capacity model, this many client hours a week, each project eats roughly this many, lets you spot when you're about to overcommit before you've promised it. It also tells you exactly when hiring a contractor or automating a step pays for itself, namely when demand reliably exceeds capacity. Plan capacity deliberately and you protect both your delivery quality and your own sanity.