What is Spiral Model?

Spiral Model is a combination of a waterfall model and iterative model. Each phase in spiral model begins with a design goal and ends with the client reviewing the progress. The spiral model was first mentioned by Barry Boehm in his 1986 paper.

The development team in Spiral-SDLC model starts with a small set of requirement and goes through each development phase for those set of requirements. The software engineering team adds functionality for the additional requirement in every-increasing spirals until the application is ready for the production phase.

What is Spiral Model? When to Use? Advantages & Disadvantages

Spiral Model Phases

Spiral Model PhasesActivities performed during phase
  • It includes estimating the cost, schedule and resources for the iteration. It also involves understanding the system requirements for continuous communication between the system analyst and the customer
Risk Analysis
  • Identification of potential risk is done while risk mitigation strategy is planned and finalized
  • It includes testing, coding and deploying software at the customer site
  • Evaluation of software by the customer. Also, includes identifying and monitoring risks such as schedule slippage and cost overrun

When to use Spiral Methodology?

  • When project is large
  • When releases are required to be frequent
  • When creation of a prototype is applicable
  • When risk and costs evaluation is important
  • For medium to high-risk projects
  • When requirements are unclear and complex
  • When changes may require at any time
  • When long term project commitment is not feasible due to changes in economic priorities

Advantages and Disadvantages of Spiral Model



  • Additional functionality or changes can be done at a later stage
  • Risk of not meeting the schedule or budget
  • Cost estimation becomes easy as the prototype building is done in small fragments
  • It works best for large projects only also demands risk assessment expertise
  • Continuous or repeated development helps in risk management
  • For its smooth operation spiral model protocol needs to be followed strictly
  • Development is fast and features are added in a systematic way
  • Documentation is more as it has intermediate phases
  • There is always a space for customer feedback
  • It is not advisable for smaller project, it might cost them a lot