What is bottom-up estimation?

Bottom-up estimation is a method of estimating the time and resources required for a project, where the estimate starts with the smallest tasks or components and then sums them up to get the overall estimate.

Unlike top-down, where the estimate is made at the level of the entire project, bottom-up allows for a more accurate consideration of details and risks, as each task is estimated separately.

Example: a team breaks down a project into individual tasks (e.g., module development, testing, documentation), estimates the time for each, and then adds these estimates to obtain the total duration.