The complete guide on software development time estimation

10 min read
February 17, 2023

Ever heard of a ‘black swan’ project?

It describes a software project that overshoots projections so much that it stretches the development time by 70%.

The surprising bit? One in six IT projects ends up becoming Black Swans, according to a Forbes article.

The truth is that giving an accurate project timeline is a very hard task. There’s just so much variability and uncertainty that it’s becoming a near-impossible feat.

Fortunately, there are ways around this. This article will discuss software development timelines and the tactics you can use to estimate them better.

The software development timeline

Before estimating development time, we must first know its components and how much time to spend on each. Here’s a brief rundown:

Product discovery

Any software project starts with product discovery. This process aims to validate the app idea and explore ways to implement it effectively.

Product discovery phases

Source: Net Solutions

During product discovery, the development team and client discuss the product’s scope in detail. This includes the app’s goal, the problem it’s trying to solve, and a profile of its intended market.

From here, you can determine the app requirements. This includes the deliverables, tech stack, milestones, and expertise required for the project.

You’ll also get a rough idea of the estimated cost and timeframe.

You’ll sometimes do simple wireframes and app flows during product discovery. This can help paint a rough picture of your app’s appearance once launched.

Product discovery is hands down the most critical phase of the development cycle.

Many of the top causes for failed projects, such as changing objectives or unidentified risks, can be solved with proper product discovery.

Common causes of project failure

Source: Acceler8 Consultancy

As such, you need to take your time in this phase. A good benchmark is around 2 – 8 weeks or around 10% of your total development time.

Software design

Once the software requirements are well-defined, the next step is to define the software design.

In this phase, the UI design will be finalized through wireframes and mockups. For larger projects, an interactive prototype can also be used to validate the app UX with end users further.

Wireframe vs mockup vs prototype

Source: Moqups

Software design takes 5 – 7 weeks on average, with 2-3 weeks allotted to UX design and 3-4 weeks for UI design.

Obviously, the more visually demanding your app is, the longer this phase will take. For instance, adding animations and custom gestures can easily add weeks to this estimate.

Most of the delays happen because of the back-and-forth between the designer and the client for approval. Also, conducting usability testing with a prototype can further stretch timelines.

Developing the software

In this phase, the development team takes the UI design and prototype and turns it into a working program. They do this by writing code.

This is where roughly half of your development time is spent. On average, that translates to around 12 – 16 weeks, split evenly between your software’s front and back ends.

However, you speed this up if you develop them simultaneously.

App development timeline

Source: Existek

The main reason for delays in this phase is mainly the complexity of the software project.

The size and expertise of your development team also play a role, as more people with good skills can finish coding much faster.

Software testing

The testing phase ensures that the software is as bug-free as possible before launch. Because of this, the QA team must be very thorough – which could take time.

Testing is perhaps the most variable of the software development phases. Depending on the number of bugs found, it could take a few weeks to months.

If there’s a critical issue, the project could return to the development phase, stretching the timeline even more.

Testing tools can also speed up and slow down this phase. For example, using automated testing platforms like Selenium and Appium enables the QA team to run repetitive tests rapidly.

On average, though, expect to spend 2 – 3 weeks in the testing phase.

What affects the duration of development

It’s no secret that estimating the software development timeline is challenging at best and near impossible at worst. And it’s mostly due to these four reasons.

Design complexity

A complex app design, with a customized UI and animations, generally takes more time and effort to develop. Thus, it will stretch your development timeline significantly.

Consider how easy it is to create an app with a simple UI. You can always rely on iOS or Android’s native libraries and pre-built components to quickly put together your app interface.

In these cases, estimating the time you’ll need to design your app is easy.

Apple design resources

Source: Apple Developer

But it’s not so easy with a large, custom app design. That’s because you must create most of it from scratch, which could complicate your estimation.

Animation, for example, is a complex process that could easily delay your project.

On average, expect to add 9 – 10 weeks when designing a custom app UI.

Software complexity

As with app design, software complexity is directly proportional to development time. In other words, the more features or advanced functionality it has, the more time it takes to develop.

To give you an idea, a simple app with only a few screens takes around 3 – 5 months to build.

Contrast that with a feature-packed app like Uber or Facebook, which can easily take 9 months or more to code.

Mobile app development timelines

Source: Signity Solutions

This isn’t at all surprising. Complex features require more coding and testing time to get right.

Plus, you need buffer time to account for problem-solving and other roadblocks. On top of that, feature-rich apps take more time to maintain and update.

To make things worse, development times for complex projects are also harder to estimate. Because of the many variables involved, it’s easy to miscalculate your prediction.

Ability to integrate

Integration is now becoming the norm with modern apps, as it’s rare to find a standalone app these days.

Unfortunately, integrating an app with existing software isn’t an easy task. It takes time and effort that, consequently, stretches the development timeline.

This is especially true if you want to integrate into legacy systems.

Since older software may not have APIs or data access layers (DALS) to facilitate integration, you’d need to build them from scratch.

3 common types of legacy systems integration

Source: ModLogix

Fortunately, there are ways to shorten the integration process and simplify your estimation.

For instance, you can use third-party plug-ins like Open banking or Twilio to connect your software with other services quickly.

Database migration

Migrating data from an old system can seem trivial, but only if everything is in perfect order. In the real world, this rarely happens.

Often, data is incomplete or fragmented, so it needs to be processed first. Or it could be that the data format is incompatible with the new system, so it needs to be converted first.

That’s why you often need to create scripts to handle this. And that takes time.

And it doesn’t end there. Once the data is imported, you must test and optimize it to ensure good performance.

Here’s an overview of the data migration steps.

Data migration steps

Source: Eclipse Consulting

To further complicate the issue, it’s hard to estimate how long data migration would actually take.

At best, it just takes a few days. But when working with a large volume of problematic data, it could stretch to months.

Methods for estimating development time

This section will go through three of the most popular methods for estimating development timeframes.

Analogous estimation

Analogous estimation is a technique where you predict the time required for a project based on a similar project in the past.

For instance, if you saw that it takes your team six months on average to create a mobile wallet app, you’d give roughly the same estimate for any mobile wallet app in the future.

Analogous estimation

Source: Project

Analogous estimation is the best route if you don’t have enough time and data available to give a more accurate timeframe. It’s also relatively easy, requiring no fancy calculations or models.

However, its biggest flaw is inaccuracy. That’s because analogous estimation is based on the assumption that a past project is exactly the same as your current project.

That’s simply not the case.

Factors such as unexpected issues, a shifting market, and a different tech stack could skew your estimates. Even a new team member can impact development times.

The key to making analogous estimation work is to pick a past project that’s as close to your current one as possible.

It’s also beneficial to look at the project’s metrics, like lead time and code churn, to give a better picture.

For this reason, analogous estimation is impossible for newer development teams with no project history.

Bottom-up estimation

In bottom-up estimation, you break a project down into individual tasks. You then use these as the basis for predicting your timeline.

For instance, let’s say you determine that the project requires roughly 50 individual tasks, each requiring an average of four days to complete.

Thus, your software should take 200 days to complete, or around 6 – 7 months.

Bottom-up estimation

Source: Invoice Owl

Bottom-up estimation is a much more accurate method than analogous estimation. That’s because you can account for as many factors as possible.

While breaking down your project, you’ll inevitably tackle bottlenecks and issues, which you’ll need to compensate for.

For example, if your team lacks cybersecurity skills to create a fintech app, you might add additional time to account for training and research.


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Of course, the flip side is that bottom-up estimation takes more time and effort because you need to analyze a project and gather requirements.

The larger the project, the longer bottom-up estimation takes, making it hard to scale.

You also can’t rely on past estimations and would need to start from scratch every time.

Despite these shortcomings, bottom-up estimation is one of the better methods for getting accurate timelines. So if you have the time and resources, go for it.

Parametric estimation

Parametric estimation uses a combination of historical and statistical data to calculate a time prediction. In other words, it takes the best of both bottom-up and analogous methods.

Parametric estimation

Source: PM Study Circle

Because it considers many variables, parametric estimation gives highly accurate predictions.

In practice, however, its accuracy depends on the statistical model used and the quality of the data.

Parametric estimation is also reusable. Once you’ve refined an algorithm and proven it works, you can apply it to future projects.

In fact, a parametric model tends to get more accurate with time.

The number one drawback of this method is the huge time commitment and expertise involved, as you’ll need to gather data and crunch the numbers.

Thus, this approach is best for larger projects.

Need to estimate your project timeline?

In reality, estimating a project timeline is equal parts art and science.

You can rely on knowledge and tactics. However, it’s the experience that will really help give an accurate prediction.

And that’s what we can bring to the table. With a handful of successful apps completed on time and on budget, we believe we can help you achieve the same in your project.

Interested? Schedule a free consultation with us today, and let’s talk!

Written by

Marin Luetic


A seasoned software engineering executive, Marin’s role combines his in-depth understanding of software engineering processes (particularly mobile) with product and business strategies. Humbly boasting 20+ years of international experience at the forefront of telecoms, Marin knows how to create and deliver state of the art software products to businesses of all sizes. Plus, his skills as a lifelong basketball player mean he can lead a team to victory. When he’s not hopping from meeting to meeting, you’ll find Marin listening to indie rock, or scouring the latest IT news.

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