Estimating is a core part of project planning. Your schedule, budget, and resource plan are only as strong as the estimates behind them. While estimation is never perfect, using structured techniques makes your numbers more realistic—and your plans easier to defend.

Analogous Estimating

Based on historical data from similar projects or activities.
Example: Project A is similar in size and complexity to Project B, so it will likely take a similar amount of time (with adjustments).

Parametric Estimating

Based on calculations using historical rates and project parameters.
Example: Activity A takes X hours, we can determine the duration by multiplying the quantity of the activity required and the working hours. So, if Activity A takes 2 hours per unit and you need 50 units, the estimate is 100 hours.

Three-Point Estimating

Based on a formula, where most likely, optimistic, and pessimistic ranges for the activity suration or cost are summed and divided into three to reduce bias.
Formula: (Optimistic + Most likely + Pessimistic) / 3
Example: (4 + 6 + 10) / 3 = 6.67 days

Bottom-Up Estimating

Builds the estimate by adding up estimates for lower-level tasks (often individual tasks from the WBS).
Example: Estimate each task, then sum them to get the total project cost or duration.

Each technique has its place - early estimates often rely on analogous, detailed plans benefit from bottom-up, and three-point helps when uncertainty is high. The goal isn’t perfection -it’s a realistic plan you can manage and communicate confidently.