Bottom-Up Estimating is a project management technique used to estimate the total cost or duration of a project by breaking it down into smaller, manageable components. Each component is assessed individually, allowing for a more accurate and detailed estimate. This method is particularly useful for complex projects where various tasks and resources need to be considered. Once all individual estimates are calculated, they are aggregated to form the overall project estimate. This approach helps identify potential risks and resource requirements early in the planning process, leading to better decision-making and project execution.