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Why Asking Developers for Time Estimates in Software Projects Is a Terrible Idea and How to Bypass It With Scrum

I have worked in many software projects, having been lucky to be in the initial team of several software products. Besides, having acted both as a Developer and as a Product Manager has allowed me to have a wider view of what usually causes most friction between business and engineering: time estimates.

Picture of a woman pointing to her watch as if you were late. Typical management or customer reaction to delayed software projects

It usually starts with managers or stakeholders asking “when will <this idea> be ready?” and it is usually followed by developers racking their brains to give a specific date… Needless to say, that date is likely to be dreadfully wrong, as it is the norm in the industry. There is a near-total inability of developers to predict how long a project will take, so time estimates are usually worthless.

However, using Scrum properly (along with some XP practices) we can avoid the uncomfortable tension of asking developers for time estimates. Instead, we can calculate release dates automatically, getting infinitely more accurate time estimates, while saving all the arguments and keeping team morale high. How? Keep reading!

1. The problem: Time estimates in Software Projects fail dramatically

The topic of delay and over-budget in the software industry has been widely discussed, including reports such as this one by Harvard Business Review, later commented in this InfoQ post. A conclusion of this report is: “If you want to avoid the slow death caused by IT projects you must be prepared not only to spend 400% more than planned on the project, but to reap only 25% of the expected benefits. If you keep this in mind you can possibly prevent a company from being killed by an IT project”.

Moreover, since 1994 Standish Group has been releasing their CHAOS Reports every year. These reports are a relevant snapshot of the state of the software development industry. The last CHAOS Report (2015), shows that even nowadays, only 29% of Software Projects are successful (defined as on-time, on-budget and with a satisfactory result). This report highlights one of the key variables affecting success rates: the approach used to manage projects (Agile vs Waterfall). Agile Methodologies showed a 39% ratio of successful projects, while Waterfall only 11%. This seems to be closely related to the way in which we deal with estimates and changes in each case.

1.1. Let’s assume we never know how long it’s going to take

I bet some of you consider yourselves great estimators. However, the overconfidence of software developers is a well-known issue. Dan Milstein describes it in this great article, concluding that “one of the deepest challenges involved in writing software is the near-total inability of developers to predict how long a project will take”. In this article, Dan writes in detail about all the issues that make software projects so hard to estimate. Among others, factors such as the impossibility to write fully detailed specifications (as he says, to do so you have to be actually writing the software), uncertainty and unpredictability (about the product itself, the market, the technologies being used…) and the uniqueness of software projects (which makes it almost impossible to relate to similar projects for estimates since there are always major differences).

Moreover, in this Hacker News thread, many developers acknowledge lying when giving estimates, which is considered an standard practice to deal with customers or management. In the same thread, another interesting recommendation for management is to add a load factor of 2-5x to developer estimates, describing it also as an “industry standard”. As you may guess, these practices are not helping the industry to improve, but rather the opposite. Should we keep ignoring the elephant in the room?

1.2. How time estimates are seen by developers vs managers

There is an increasing tendency among developers against giving estimates in software projects (see #NoEstimates). To a certain extent this makes total sense, since time estimates have been proved to fail dramatically in the industry (especially for tasks that take more than a day to complete). Besides, developers are usually the ones paying the bill of a failed estimate, by working long hours and suffering great stress due to management pressure to meet deadlines. This usually leads to poor team morale, friction, loss of credibility and many other problems, as described in detail by Richard Clayton in his article “Software Estimation is a losing game”.

On the other hand, since I have been manager and CEO apart from developer, I know how useful would time estimates be from the business side (either to calculate costs for a customer that wants a fixed-price contract; or to ourselves, to plan marketing actions, meetings, etc…). However, we must asume that calculating accurate time estimates for software projects is simply not possible. Putting pressure on developers to give us time estimates will simply make them lie to us, giving an estimate that is going to be dreadfully wrong. As we have explained before, they just don’t know how long is it going to take.

I guess I don’t need to mention that, if developers are not able to give us an accurate time estimate for a software project to be finished in; managers (with no technical background or having spent the last few years out of development) are much worse at it.

1.3 The role of evil contracts

If there is something to blame above anything else, that would be the magic fixed-everything contract (where price, time and scope are set at the beginning of the project). Those contracts are the root of all evil. The recipe for disaster starts by “setting the cost” of development beforehand (when we know the least about the software being built) and presenting it to the customer in the form of a contract. This contract will describe how a “fixed software” (that in most cases is just a vague idea) will be developed for a fixed price and, of course, ready for a fixed date.

That is how all this madness usually starts.

Most managers and salespeople love this approach. For them it is so simple… To “calculate the cost” they just have to ask developers for time estimates, add some contingency time and then do the math (calculating salaries, other expenses, benefits…) and that’s it! Ready to convince the customer! What can go wrong?

Well, now that you know that having accurate time estimates for software projects is simply not possible, as a manager you can choose more realistic contract approaches, or you can assume the risks of doing fixed-everything contracts, based on those more-than-likely-wrong time estimates. But if you choose the latter, don’t blame developers when deadlines are not met.

If you have a team of professional and commited developers, they will be doing their best all the time, trying to do things as quickly as they can (as @dhh says, ASAP is implied). Sadly, too many times managers end up using the whip to make developers achieve the impossible. At the end, the imposible is not achieved, software quality goes down because of the rush (causing more delays due to constant bugfixing and poor code-maintainability), team morale is almost cero, everyone suffers burnout and the customer gets angry. Nobody wins.

That being said, even if you use fixed-price contracts (or “fixed-everything” contracts), the approach I will describe below will help you minimize problems, by following an iterative and incremental development process. With this approach, your team will always work in the most important features, releasing an incremental version of the product every few weeks. By doing this, you will always have working software to ship to your customer. If the deadline arrives and the project is not finished, at least the X more important features will be developed. And working software will be available. Moreover, if you manage to involve your customer in the process, you will benefit from showing her the incremental releases. Among other things, you will get valuable feedback, anticipate changes and build trust. Therefore, customer relationships will improve and contract changes will become easier to deal with. Nonetheless, the best part of this approach is that you will also be able to calculate more-realistic release dates, without asking developers for time estimates.

2. The solution: Calculating release dates based on (project-dependant) Team Velocity with Scrum

So, as a manager, how can Scrum help you?

Unfortunately, Scrum has become kind of a buzzword in the last few years and many people in the software industry say they use Scrum when in reality they are not following many of the key principles… If you are new to Scrum, I encourage you to read The Scrum Guide which is a fantastic 16-pages document written by the creators of the framework describing its principles. Also, if you are new to User Stories, here you can find a great article comparing User Stories, use cases and requirements. Too tired to read? Then a good alternative are these great videos about the scrum framework.

Once familiar to the Scrum Framework, all we need to do to get much more accurate time estimates for our software project, is to follow 4 simple steps that I will describe below. If you follow these steps properly, you will get infinitely more accurate time estimates than the ones you may get by asking developers. And what is even better, you will be able to rearrange the pending features (adding, removing or moving them) and get approximate release dates automatically.

2.1. Create a Product Backlog with User Stories as a first step

Not asking anything to developers yet; no coding. Sit down with some stakeholders, business partners or customers and try to describe what you think the product should be, according to what you know for now. Creating some simple wireframes, discussing them lightly and iterating a bit over them is usually the best way. But keep it simple. As an advocate of Lean Startup myself, I know that it is impossible to know all the features or details of a product at the beginning. This exercise will simply help you do some customer discovery, clarify your initial hypotheses and come up with a few User Stories that define an MVP (Minimum Viable Product) that you will be able to release quickly to keep learning about the business, following an iterative and incremental development process.

So, once you have enough information about the product and the market that you are able to design an MVP, try to describe the most important features the product should have (as User Stories) and prioritize them when creating the Product Backlog. Since User Stories are about functionality, wireframes are usually very good help. They can be added as part of the Acceptance Criteria of the User Stories.

My favourite tool for managing Scrum is Jira, which includes a great backlog-management tool. However, there are many other tools available, including Trello, which I also use as a kanban board for smaller projects. For wireframing, there are also many good tools available. One of my favourites is WireframeSketcher, due to its IDE and CVS integration. Balsamiq and Moqups are great alternatives too.

After creating the initial Product Backlog, you will have a much clearer picture of the MVP you are going to build and therefore, you will be in a better position to present it to developers.

2.2. Estimating all User Stories in the backlog based on effort points

Once you have created your initial Product Backlog and prioritized the User Stories, it is time to have the first Product Backlog Refinement meeting with the Scrum Team (which includes the Development Team). Our goal would be to estimate all User Stories in the Backlog, but instead of time we will be using effort points. Each User Story will have X points. A common approach is to use the Fibonacci scale for those points.

Since it is very important to be consistent when estimating User Stories I usually encourage the team to find the easiest User Story in the backlog and give it a 1 and then find the hardest one and give it either a 13 or a 21. That way you have created the team’s effort scale, making it easier to estimate the remaining User Stories based on a scale that is totally dependent on the project.

“Wait! But this numbers are not useful for me!”, a manager said. Hold on, they definitely are. For now they tell you which are the easiest User Stories and which ones are the hardest. But even better, in a few sprints they will help you calculate when will the project be finished or when will a specific User Story be done, according to its place in the backlog. And this estimate will be a much more precise that any you could have ever got from asking developers for time estimates.

If in the future new User Stories appear (they will), all you will have to do is to add them to the backlog, placing them according to their relative priority compared to the rest of the stories; and save a day during the sprint to conduct the Backlog Refinement Meeting, when the new stories will be estimated. The most important task of the Product Owner (that would be your role in Scrum) is to keep the backlog updated, estimated and prioritized, in order to make it useful to predict release dates.

2.3. Keep effort-based estimates time-independent

Even though in Agile Methodologies time estimates are usually replaced by effort points (using scales such as Fibonacci or t-shirt sizes), some managers simply establish a link from those points or sizes to “their equivalent” in time, and they usually do that publicly, which means that everybody goes back to time estimates; thus ruining the whole thing again and making developers hate agile too (even though what they hate is a bad implementation of agile methodologies). The key of using an effort-based system for story points is precisely to keep estimates separated from time. The relative “effort” of a task is a much easier concept to analyze for developers, especially when comparing the different User Stories of a project.

2.4. In the first few sprints Team Velocity and Capacity are yet unknown

When planning a sprint, the team will pick User Stories from the top of the backlog until they consider it is enough work for the sprint. Then, during the sprint review you will discover whether all user stories were completed as expected or if there were some changes (e.g. the team was not able to complete all the user stories, or by constrast, all stories were completed early and some more were added to the sprint).

As you will see, in the first few sprints there is usually some error when comparing what the team planned to achieve and what it did actually achieve. However, this error will become smaller and smaller over time, achieving a constant speed or Team Velocity (measured in story-points per sprint).

At this stage it is important to mention that having a fair Definition of Done is key to success, although it is beyond the scope of this article.

2.5 After a few sprints you will be able to accurately estimate release dates, based on Team Velocity

Once a few sprints have passed you will realize that, if story-points estimates are kept consistent, the team usually achieves a similar number of story points per sprint.

Since you are doing your job of keeping the backlog updated, prioritized and estimated in story points by the development team, you will able to forecast when a particular story will be finished.

An example will make it clearer:

Let’s say the Development Team completes 50 points per sprint and each sprint takes 15 days. If you want to know when will a particular User Story be finished, all you need to do is to count the number of story points that are above it, plus its story points. Let’s say User Story X has 160 points above and it has 8 points itself. This means that it will be finished in 168 story points. Since in each sprint the team is completing approximately 50 points and since team estimates are consistent, the story you are looking for will be finished in 4 sprints time, which means 2 months.

The same process can be applied to know when will the whole project be finished, just taking the last User Story you have in the backlog for the calculations explained before.


With this management approach you will get really accurate time estimates without asking for them; you will keep team morale high, avoid burnout and improve productivity. Besides, you will be able to automatically forecast the impact of changes in the timing of the project.

This solution contributes to improve business-engineering relationship and trust; improve software quality and reduce costs in the long-run. Besides, if you involve customers in the process, customer relationships and trust may improve considerably; making it easier for both parties to deal with change, preventing many deadline-related conflicts.

Now, join the conversation: How do you deal with time estimates in your company?