Fixed price vs time and materials: how to choose.
The engagement model decides who carries the risk. Fixed price gives cost certainty, time and materials gives flexibility, and a dedicated team gives steady capacity. Here is when each one fits, and how we reduce the risk in each.
- Fixed price
- Time and materials
- Dedicated team
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- Fixed priceCost certainty for a clear scope
- Time and materialsFlexibility, with open-ended cost
- Dedicated teamSteady capacity for a long roadmap
- Five questionsTo choose with confidence
Is fixed price or time and materials better for software projects?
Fixed price is better when scope is clear and stable and you need cost certainty. Time and materials is better when scope is unknown or changes often, but the cost is open-ended. A dedicated monthly team suits long-running roadmaps. Stack18 avoids open-ended billing: we start with a fixed-price discovery, then run fixed-scope projects or a monthly team.
The options compared.
| Fixed price | Time and materials | Dedicated team (monthly) | |
|---|---|---|---|
| Cost certainty | High: the price is agreed for the scope | Low: cost grows with the effort | Predictable monthly cost, scope varies |
| Flexibility | Changes are agreed as scope changes | High: scope can change freely | High: priorities change every sprint |
| Scope clarity needed up front | High | Low | Low to medium |
| Who carries the risk | Mostly the vendor, within the agreed scope | Mostly the client | Shared through regular prioritisation |
| Best for | A defined product, migration or platform | Exploratory work with unknown scope | A long-running roadmap |
| At Stack18 | 1–4 week discovery, then 4–16 week fixed-scope projects | We avoid open-ended billing | Dedicated pod, billed monthly, with Enterprise Pods on annual contracts |
Where each model wins.
No model is best everywhere. This is where each one fits, and what to watch for.
Fixed price
- Best when
- Scope is clear and stable, and cost certainty matters more than flexibility.
- Trade-off
- Changes need agreement, and unclear scope causes friction, so a good discovery matters.
- Typical result
- At Stack18: a fixed-price discovery of 1 to 4 weeks, then a fixed-scope project of 4 to 16 weeks.
Time and materials
- Best when
- Scope is unknown or changes constantly, such as early exploration.
- Trade-off
- Cost is open-ended and needs active budget control from your side.
- Typical result
- Not how we price: an open-ended bill shifts the risk to you.
Dedicated team
- Best when
- You have a long-running roadmap that needs steady capacity release after release.
- Trade-off
- It is an ongoing commitment, and the value depends on how well you prioritise.
- Typical result
- At Stack18: an ongoing monthly pod, or a 12 to 36 month Transformation Pod.
Which model fits your project?
Think about the work you have today, not the work you hope to have.
How clear is the scope?
A clear, stable scope fits fixed price. If you cannot describe it yet, start with a fixed-price discovery.
How often will priorities change?
Frequent change favours a dedicated team. Stable requirements favour fixed price.
How firm is the budget?
A hard budget favours fixed price, so the cost is agreed before work begins.
How long is the horizon?
A project of weeks to months suits fixed price. A roadmap of years suits a dedicated team.
Who owns product decisions?
A strong internal product owner suits a dedicated team. Without one, a defined scope protects you.
How we reduce the risk in each model.
We never start with a blank cheque. Every engagement begins with a short, fixed-price step, such as a two-week Discovery Sprint, so you see the plan, the team and the price before committing more. You then get working software every week through demos, so problems surface early under any model.
Common questions.
Does Stack18 work on time and materials?
We avoid open-ended billing. We start with a fixed-price first step, then run a fixed-scope project of 4 to 16 weeks or a monthly dedicated team.
What is a Discovery Sprint?
A two-week, fixed-price engagement that turns a goal into a scoped plan, a team and an estimate, so you can decide before committing to a build.
What if the scope changes during a fixed-price project?
Changes are agreed as scope changes. Weekly working demos help you spot what needs to change early, while it is still cheap to change.
When should we choose a dedicated team?
When you have a long-running roadmap and want steady capacity release after release. Stack18 offers a dedicated pod billed monthly, and Enterprise Pods on annual contracts.
How do we avoid overspending?
Agree the scope and price before work starts, review working software every week, and decide at each milestone whether to continue.
Can we move from one model to another?
Yes. Many engagements begin with a fixed-price discovery, move to a fixed-scope project and then extend into a dedicated team.
Related guides and pages.
Not sure which fits? Ask us.
Tell us where you are and where you want to be. A senior specialist will reply within one business day with next steps.
- Free 30-minute consultation
- Indicative estimate after the call
- NDA available on request