Blog: Art of Agile Estimation | Inflectra

Blog: Art of Agile Estimation

May 22nd, 2019 by inflectra

Frequently, people wonder whether agile estimation approaches differ completely from the plan-driven approaches in project management. While each framework has its own uniqueness in their approach to gathering estimates, the nature of estimates gathered should be considered in relation to the project or product lifecycle.

How much does estimation approaches differ?

When viewed from the vantage point of project or product lifecycle, there is not a vast difference in the estimation gathering process between agile and plan-driven approaches. However, if we fail to recognize the nature of estimate and the lifecycle stage where estimate is gathered, then we often gravitate towards the nomenclature used thinking that the top-down, bottom-up, and 3-point estimate apply only in plan-driven framework and affinity estimation, planning-poker, and relative sizing apply only in agile framework.


Accuracy of Estimates

When estimates are gathered, the level of accuracy plays a critical role in the amount of effort spent in gathering the estimates. When organizations decide on a strategic objective and evaluate a program or project to address the strategic need, this estimate is called a screening estimate focusing on whether this work can be done. This screening estimate uses an order of magnitude using heuristics or analogous reasoning and hence has a high margin of error. Subsequently, when decision is made to evaluate this initiative further, we move towards the technical, operational, and environmental feasibility analysis to come up with a decision estimate. This may take additional time such as market research and hence increases the precision somewhat compared to the screening estimate. The feasibility analysis then leads to the preliminary evaluation of the budget involved in implementing the work. This preliminary estimate is called the budget estimate. All these estimates are still at a higher level, but the goal would be reducing the amount of error in the estimate.

Subsequently, if the organization decides to move forward, additional estimates are gathered. The complexity, sensitivity, and visibility of the initiative will mandate the level of estimate gathered. This is called the plan estimate used to build the project schedule as part of the integrated project management plan development. Nevertheless, this estimate is a tentative estimate giving the organization the decision to move forward with the project. Only when the actual work is done as part of the project execution, detailed estimates are gathered to gain increasing confidence on when the project will be delivered.

Art of Agile Estimation

If you map these ideas to the art of estimation in agile approaches, one can clearly see when estimation should not be done and what level of estimation is required in agile framework. When a major new idea is conceived, it is often a high-level “dream”. This idea needs to be broken down into epics, which are still at a very high level. For instance, the big dream of a huge house may become an epic castle. Neither of these ideas and epics should be estimated.

As time progresses with increasing level of granularity, themes develop around the castles on the types of big houses followed specific features. As we iterate the epics into themes and features, we are start working through the screening, decision and budget estimates iteratively. So, the big house theme is broken down into duplex home. Since these are relatively better than the ideas and epics, the themes and features are estimated in T-Shirt sizes (Small, Medium, Large, X-Large) or Coffee-Cup sizes (Tall, Grande, Vente, Trenta).

But, what we build are not features. These then get broken down further into user stories. The user story indicates the deliverable that needs to be built. Like the project schedules in the project management framework, the deliverables are decomposed into the tasks or activities even in agile framework. But, the user stories are estimated in story point, but the tasks are estimated in hours.

Estimation is therefore not only science but also an art. One must understand all the techniques so that the right estimation approach can be used as well as adapt the techniques to the situation. Learn more by listening to the webinar on these additional thoughts on estimation.


Dr. Sriram Rajagopalan is a project management guru with extensive software development and project management experience in many industries. Dr. Rajagopalan lead Inflectra's agile project management webinar series called: Deeper Dive Into Agile: Practical Tips On Managing Agile Projects


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