Roll-Off Dumpster Rental isn't a smaller version of a standard rental. It is the general-purpose container that covers almost any job, sized from 10 up to 40 cubic yards, and that's what you're actually paying for. Carry this into the conversation: the yardage describes space while the truck is bound by axle weight, so the tonnage allowance runs out first.
Two limits apply at once: how much room you have, and how much weight you're allowed to put in it. Debris rarely respects both at the same time. Ask around and you'll find homeowners and contractors renting for this more than anyone else, choosing from containers as large as 10 or 20 or 30 or 40 yards. Two questions decide this fast: what's going in, and how many days it'll take to fill it.
A typical cleanout carries some of everything, so it neither maxes out the weight limit nor stacks past the rim first, and sizing comes down to a straightforward volume guess. Listed capacity is measured in cubic yards, not by how comfortably debris fits -- a container rated for the job usually still needs everything broken down flat to actually hold it. Between ordering too big and ordering too small, the safer mistake is still a mistake. Get the estimate right instead.