Estimating the time required to complete a task is riddled with pitfalls.Let’s start with two key concepts you must understand — after managing and designing projects for over 20 years, I’ve seen these patterns play out again and again.Hofstadter’s lawHofstadter’s law is a self-referential adage about time that goes like this:“It always takes longer than you expect, even when you take into account Hofstadter’s law.”This law highlights how difficult it is to accurately estimate the time required to complete complex tasks. Its recursive nature reflects the widespread experience that, no matter how complex a task appears, calculating the time needed is hard, even with our best efforts. (See the header image.)Why is that?Optimism biasThe main reason stems from the tendency known as optimism bias — the inclination to be overly optimistic and thus overestimate favorable outcomes. In fact, we tend to overestimate our own abilities as well.It’s worth noting that this bias is actually quite necessary for humans: without it, we wouldn’t take risks, start businesses, or grow. However, when it comes to estimation, it can seriously backfire. This phenomenon naturally leads to…Planning fallacyOverly optimistic forecasts about the outcomes of plans are almost everywhere. Daniel Kahneman and Amos Tversky introduced the term planning fallacy to describe how we consistently underestimate the necessary resources (money, time) when planning complex projects. This phenomenon pushes us toward optimistic planning. Unsurprisingly, we’re much more realistic when reviewing someone else’s plan.In short:We overestimate favorable outcomes and our abilities, and we underestimate the required resources and constraints.What can we do?As I mentioned earlier, I’ll share how I personally handle this. The phenomenon is not new, and there are countless methods available.2x + 15 ruleFor smaller tasks (~1–20 hours), I use this technique. I look at the task, estimate the number of hours, double it, and add 15 minutes. The extra 15 minutes is to get started and immerse yourself in the task. Most of the time, it works quite well and is incredibly simple.Hofstadter multiplierMy teammates track and record the actual time spent on tasks, which is useful for several reasons. First, it helps everyone gain experience with how long typical tasks take, which they can then compare to their own estimates, improving their estimation skills. Second, you can determine your own — or a particular person’s — so-called Hofstadter multiplier. We’re all different, so this is a more advanced, personalized version of the 2x + 15 rule.Complex projectsThe earlier solutions work well for simpler tasks, but complex projects require additional considerations. But first, it’s important to clarify one question:How much energy can you, or do you want to, invest in the estimate/proposal?From there, more questions arise:Is it a rough indicative proposal or a detailed, itemized one?What inputs, expertise, and professionals are needed for the estimate?Is all necessary information available?How much capacity do you have (if any) for the estimation and/or execution?Do you realistically have a chance of winning the work? :)Your answers to these questions will influence the path you choose.Going back to the planning fallacy for a moment: it can be mitigated by involving a third party or by relying on real data from similar past projects.That’s why it’s crucial to keep precise records of the time spent on every task so that the data is available later.You will log the time for every task. — Obi-Wan KenobiMoving on…In an ideal world, the best approach is for the team that will actually execute the project to estimate it together. But consider how much it costs if a 4–5 person team individually reviews and interprets the materials, discusses them together, collects missing information, breaks down the project into items, and estimates each one using some method. It’s incredibly time-consuming and expensive.Therefore, as a substitute, it’s good to have an experienced person who’s seen many projects and/or to rely on actual hours from similar past projects. In this case, you only need to account for the differences and unknowns (the risks) at the time of the proposal. Estimation becomes much simpler, faster, and cheaper.For indicative proposals, I almost always use this latter method, with one important addition: always assume a ±20% variation.Whoa, be careful!It may seem like you’ve done something similar before, but hidden behind the scenes are major differences. This can lead to nasty surprises if you rely on data from nearly similar projects. In such cases, it’s wise to consult multiple external teams to benchmark the work. This helps refine the estimate and creates a healthy competitive environment.And when a detailed, itemized proposal is necessary… There’s no shortcut: you’ll need to apply a methodology. I won’t even attempt to cover this topic here, as there are entire books written about the relevant methodologies.FinallyI’ve been in the product design profession for over 20 years, and I often play the game where, after hearing the requirements, I throw out a number almost off the top of my head. It works surprisingly often, but of course, I wouldn’t even call it indicative. Still, it’s fun.Estimating time for complex projects was originally published in UX Collective on Medium, where people are continuing the conversation by highlighting and responding to this story.