Why a burnup shows what a burndown hides

A burndown chart plots remaining work shrinking toward zero - which means if scope grows mid-sprint, the line just looks stalled, with no visible explanation why. A burnup chart tracks two lines instead of one: total scope and work completed. When scope grows, the scope line visibly steps up, and the gap between it and the completed line is what's actually left - the cause of a stalled-looking burndown becomes obvious instead of hidden.

Reading the two lines together

The completed line should trend toward the scope line, not toward zero. A widening gap between them - completed flattening while scope keeps climbing - is the clearest early signal that a sprint's scope has outgrown what the team can realistically finish, well before the last day makes it undeniable.

When to use burnup over burndown

Teams whose scope is genuinely fixed for the sprint get little extra value from a burnup - a burndown communicates the same information more simply. Burnup earns its slightly higher complexity specifically when scope changes mid-sprint aren't rare exceptions but a normal part of how the team works, and hiding that reality would make the chart actively misleading.