Estimation is harder than it looks. At first glance, it’s simply a response to the question of ‘how long will it take?’ And yet, it’s often a practice that demands constant coaching. While project teams at Quoin have been generally successful at estimating effort, our technical leads are constantly trying to improve our accuracy. Over the years, we have used different tactics to estimate the effort for stories and tasks, including loaded hours, story points, and T-shirt sizes. However, we have never found a single best approach for estimation with our client projects. What makes this so difficult? This question came up recently as we are working on new agile training courses, and I thought this deserves some attention. Perhaps the direct answer is ‘people’, but let’s look deeper into what drives the problem of estimation.