Agile guide · Agile foundations
Agile vs Waterfall: Differences and When to Use Each
Agile and Waterfall are the two broad ways to run a project. Waterfall plans everything first and moves through phases in order; Agile delivers in short cycles and replans as it learns. Neither is better in general. The right choice depends on how much uncertainty your project faces.
Key takeaways
- Waterfall fixes scope early; Agile fixes time per iteration and lets scope flex.
- Use Waterfall for stable, regulated or indivisible work; use Agile when learning will change the solution.
- Hybrid approaches are common and often the most practical.
Waterfall in brief
In a Waterfall, or predictive, project, work flows through sequential phases: requirements, design, build, test, deploy. Each phase usually finishes before the next begins and is often approved at a phase gate. Scope is agreed early, and schedule and budget are estimated from it. Changes go through formal change control.
Agile in brief
An Agile project delivers the product in small increments over short iterations. Requirements live in a prioritised backlog that changes as the team and customer learn. Each iteration produces a working result that is reviewed with stakeholders. See what is Agile project management for the full picture.
Side-by-side comparison
| Waterfall | Agile | |
|---|---|---|
| Planning | Comprehensive, up front | Continuous, at several levels |
| Requirements | Fixed early in a specification | Evolve in a prioritised backlog |
| Delivery | Once, at the end | Every iteration |
| Customer involvement | Mainly at start and acceptance | Throughout, at every review |
| Handling change | Change requests and approval | New items enter the backlog |
| Testing | A separate phase near the end | Within every iteration |
| Risk | Discovered late if assumptions are wrong | Exposed early through feedback |
| Progress reporting | Phase completion, earned value | Working increments, burndown and burnup charts |
| Typical roles | Project manager leads | Product owner, team, Scrum Master or Agile lead |
When to use Waterfall
- Requirements are clear, stable and well understood.
- The work is regulated, and documentation and approvals are mandatory.
- The product can only be used once complete, such as a building or a physical installation.
- Late changes would be very expensive or dangerous.
- The team has done very similar projects before.
When to use Agile
- The goal is clear but the best solution is not.
- Users can give regular feedback.
- The result can be delivered and used in pieces.
- Speed to market matters.
- The environment, technology or competition is changing quickly.
The hybrid approach
Most real organisations combine the two. A common pattern keeps a predictive plan for milestones, budget and governance, and lets delivery teams work in Agile iterations within each phase. Hardware and software projects often run hardware in a predictive way and software in sprints, synchronising at integration milestones.
Frequently asked questions
Agile vs Waterfall: can you switch from Waterfall to Agile mid-project?
Yes, but do it at a natural boundary, such as the start of a phase. Convert remaining requirements into a backlog, appoint a product owner and start with short iterations.
Agile vs Waterfall: is Waterfall outdated?
No. It remains the right choice for stable, regulated or physical projects. What has changed is that it is no longer the default for everything.
What is the main difference between Agile and Waterfall?
Waterfall plans everything up front and delivers once at the end; Agile plans in layers and delivers working increments throughout, letting scope change as the team learns.
Which is better, Agile or Waterfall?
Neither is better in general. Agile suits uncertain, changing work that can be delivered in pieces; Waterfall suits stable, well-understood or regulated work that only has value once complete.
What is a hybrid approach that combines Agile and Waterfall?
A mix of the two, such as a Waterfall-style milestone plan for governance and budgeting with Agile iterations for delivery. It is common in large organisations and regulated industries.
Is Scrum Agile or Waterfall?
Scrum is an Agile framework. It delivers work in Sprints of one month or less, with a usable Increment each Sprint. See Agile vs Scrum.
Agile vs Waterfall: what are examples of Waterfall projects?
Construction, physical installations, hardware manufacturing and heavily regulated system implementations are classic examples, because requirements are fixed and partial results have little value.
Agile vs Waterfall: does Agile have phases like Waterfall?
Not in the same sense. Agile repeats a short cycle of plan, build, review and improve many times, though some organisations still add initiation and closing stages around the iterations.
How is testing different in Agile and Waterfall?
In Waterfall, testing is usually a separate phase near the end. In Agile, testing happens within every iteration, so defects are found sooner.
Does the PMP exam cover Agile and Waterfall?
Yes. PMI states that the PMP exam covers predictive, Agile and hybrid approaches, so candidates need to understand both. See PMP certification.
Agile vs Waterfall: which is cheaper?
Not inherently. Waterfall can look cheaper on paper because costs are estimated up front, but late changes and building unwanted features can make it expensive. Agile spends more customer time but reduces wasted work.