Quick answer: In a fixed price contract, you agree on a defined scope and a set price before work starts. In a time and materials contract, you pay for the hours actually worked at agreed rates, usually with estimates and regular reporting. Fixed price suits small, well defined projects where requirements are unlikely to change. Time and materials suits larger or less certain projects where you expect to learn and adjust as you go. Many businesses do best with a hybrid: a fixed price discovery phase, then time and materials development in short, budgeted stages with a cap or regular review points.
Why the pricing model matters
The pricing model shapes more than the invoice. It affects how much planning happens upfront, how changes are handled, who carries the risk of surprises and how the relationship between you and your developer works day to day.
Choosing the wrong model for a project is a common cause of disputes. A fixed price on a vague scope leads to arguments about what was included. Open-ended time and materials with no oversight leads to budget surprises. Understanding both helps you pick well and set up the contract sensibly.
How fixed price works
The developer and client agree on a detailed specification, a price and a timeline. The developer commits to deliver that scope for that price.
Advantages
- Budget certainty. You know the cost upfront, which helps with approvals and planning.
- Less day-to-day involvement. Once the scope is agreed, you mainly review milestones.
- Clear deliverables. The specification defines what “done” means.
Disadvantages
- Extensive upfront specification. Requirements must be detailed before work starts, which takes time and often misses things.
- Risk premium. Developers price in uncertainty, so you may pay more than the work would cost on an hourly basis.
- Change is expensive. New ideas or corrections mid-project become change requests, each priced and negotiated.
- Incentive misalignment. If the developer underestimates, they may cut corners to protect margins. If they overestimate, you overpay.
- Arguments about scope. Ambiguity in the spec leads to disputes about whether something was included.
Where fixed price fits
- Small projects with clear requirements, such as a brochure website or a well defined plugin
- Projects that closely repeat something the developer has done before
- Discovery or design phases with clear outputs
- Situations where budget approval requires a fixed number
How time and materials works
You pay for the time spent, usually at hourly or daily rates, plus any direct costs such as licences or third-party services. The developer provides estimates and reports time regularly.
Advantages
- Flexibility. You can change priorities as you learn, without renegotiating the contract.
- Faster start. Work can begin once you agree on goals and initial priorities, without a complete specification.
- Fair pricing. You pay for actual work rather than a buffer for risk.
- Better fit for iterative development. It works naturally with agile approaches, where features are built, reviewed and adjusted in short cycles.
- Transparency. Detailed timesheets show where effort goes.
Disadvantages
- Budget uncertainty. The final cost depends on how the project unfolds.
- More client involvement. You need to review progress, set priorities and make decisions regularly.
- Trust required. You depend on the developer working efficiently and reporting honestly.
Where time and materials fits
- Larger projects where requirements will evolve
- New products, where you are still discovering what users need, as in MVP development
- Ongoing maintenance, improvements and support
- Work on existing or legacy systems, where hidden problems are likely
- Integration projects that depend on third-party systems you do not control
Comparing the two
| Factor | Fixed price | Time and materials |
|---|---|---|
| Budget certainty | High, if scope holds | Lower, managed with estimates and caps |
| Flexibility | Low | High |
| Upfront planning | Extensive | Moderate |
| Who carries estimate risk | Mostly developer (priced in) | Mostly client |
| Client involvement | Lower during build | Regular |
| Handling change | Change requests | Reprioritize the backlog |
| Best for | Small, clear scope | Larger or evolving scope |
Hybrid models
Pure versions of either model are less common than you might think. Practical hybrids include:
Fixed price discovery, then time and materials
A short, fixed price discovery phase produces requirements, technical decisions, designs and a realistic estimate. Development then runs on time and materials, with much less uncertainty because the groundwork is done. This is often the most sensible route for custom software.
Time and materials with a cap
Work is billed hourly, but total spend cannot exceed an agreed limit without your approval. You keep flexibility while protecting your budget.
Fixed price per phase or sprint
The project is split into stages, each with its own fixed price and scope. You can adjust direction between stages.
Retainers
For ongoing work, a monthly retainer buys a set number of hours or a dedicated share of a team’s time. This suits continued improvement and support after launch.
Making either model work
For fixed price projects
- Invest in a clear, detailed specification, including what is out of scope
- Define acceptance criteria for each deliverable
- Agree how change requests are priced and approved
- Tie payments to milestones you can verify
For time and materials projects
- Agree on goals, priorities and a rough budget range at the start
- Ask for estimates per feature or stage, and track actuals against them
- Hold regular reviews, weekly or every sprint
- Set approval thresholds and caps
- Ask for working software early and often, so you can judge progress by results
In both cases, a well written web development contract should cover ownership of code, warranties, support, payment terms and what happens if either side wants to end the engagement.
Questions to ask a developer about pricing
- Which model do you recommend for this project, and why?
- How do you estimate, and how accurate have your estimates been on similar work?
- How will changes be handled?
- What will I receive each week or month to see progress and spend?
- What is not included, such as hosting, licences, content or ongoing support?
- What happens if the project runs over the estimate?
A developer who pushes a fixed price on a vague, complex project without discovery may be underestimating, or planning to recover costs through change requests. A developer who refuses any estimate on time and materials work deserves caution too.
Cost is only one part of the decision
The cheapest quote is not always the lowest total cost. Poor code quality, missed requirements and rework cost more later, often as technical debt. Look for clear communication, relevant experience and a pricing model that fits the uncertainty in your project. Our guide to website development cost covers other factors that drive price.
FAQ
Is fixed price always more expensive?
Not always, but it usually includes a margin for risk. For small, predictable projects, the difference can be small and the certainty worth it.
Can a project switch models halfway?
Yes, if both sides agree. Projects that start fixed price often move to time and materials for later phases or ongoing work.
Which model do agile teams prefer?
Most agile teams prefer time and materials or fixed price per sprint, because both allow priorities to change between cycles.
How do I control costs on time and materials?
Use estimates, caps, regular reviews and clear priorities. Decide what matters most so the budget goes there first.
Choose the model that fits the uncertainty
Fixed price works when you can define the work clearly. Time and materials works when you need room to learn. When in doubt, start with a fixed price discovery phase and decide from there. If you are planning a custom application and want an honest conversation about scope and pricing, see our Custom development service.
