Estimating in Scrum is grounded in the principle of relative sizing, where items are compared to one another rather than estimated in absolute units of time. The most common unit of measure is the Story Point, which expresses an estimate of the overall effort required to fully implement a Product Backlog item. Because Developers will do the work, they are the ones who decide how many story points to assign. Teams often use the Fibonacci sequence, with values such as 1, 2, 3, 5, 8, 13, 21, and so on, because the widening gaps reflect growing uncertainty for larger items and force meaningful conversation when estimates diverge. Planning Poker is a popular consensus-based technique that uses these numbered cards, with team members discussing and re-voting until the group converges on a shared estimate.
When uncertainty is high, teams use a spike, a time-boxed investigation or experiment designed to reduce uncertainty about a technical or functional question before committing to a larger estimate. To track progress, Scrum teams use several complementary visualizations. Velocity is an empirical measure of how much Product Backlog work a team turns into a done Increment during a Sprint, and while it measures the amount of work, it is not a direct measure of productivity or value. A burndown chart shows the work remaining over time and is often used during a Sprint for the Sprint Backlog, while a burnup chart shows work completed over time and frequently includes a target line for scope. At a higher level, a Release Burndown tracks remaining work toward a release, and a Cumulative Flow Diagram (CFD) shows cumulative work across statuses over time, making bottlenecks visible.