Fixed price or time and materials – which should you choose?
Choose fixed price when requirements are clear and the project is short – that shifts the risk to the vendor. Choose time and materials when requirements are expected to change and the collaboration is long – that avoids paying a risk premium and negotiating every change. Hybrid models like capped price and target price combine the advantages and suit most larger projects.
Fixed price or time and materials isn’t primarily a question of price – it’s a question of who carries the risk and what behavior the contract encourages. Choose the wrong model for your type of project, and you either pay for risk you didn’t need to shift, or end up with a collaboration that’s more about negotiation than the product. Here’s a balanced walk-through, with a decision matrix.
The pricing model shapes behavior, not just price
Fixed price sounds safe: one sum, one commitment. But the price of that safety is twofold. First, the vendor bakes in a risk premium, often 10–20 percent, to carry the uncertainty. Second, the model creates a negotiation culture: since every deviation from the spec threatens the vendor’s margin, scope has to be defended, and every new insight during the project turns into a change-order discussion instead of an improvement. Fixed price therefore works best when there’s little left to discover.
Time and materials flips the incentives: the vendor can say yes to every improvement, and new knowledge is welcome instead of threatening. But now you carry the risk – without clear governance, the hours can roll on without the product getting any closer to its goal. Time and materials requires trust, visibility, and a client who has the energy to prioritize every week.
Neither model is “cheapest.” They price the same uncertainty in different ways: fixed price up front as a premium, time and materials after the fact as an outcome.
The decision matrix: requirement clarity vs. project length
The two variables that determine the choice are how clear the requirements are and how long the project is:
| Situation | Recommended model | Why |
|---|---|---|
| Clear requirements, short project | Fixed price | Little left to discover – risk is cheap to shift |
| Clear requirements, long project | Phased fixed price or capped price | Time itself creates change; lock one phase at a time |
| Unclear requirements, short project | Time and materials with a budget cap | Faster to explore than to specify |
| Unclear requirements, long project | Time and materials or target price | Requirements will change – build for learning, not negotiation |
A common mistake is forcing an unclear project into fixed-price form “for the sake of budget discipline.” The result is an expensive spec phase, a risk premium on everything, and a change-order list anyway – budget discipline at the cost of both money and collaboration climate. If the requirements are unclear, make them clearer with a discovery phase, or choose a model built for uncertainty.
The hybrid models: capped price and target price
Most larger projects land most wisely on a hybrid form:
- Capped price is time and materials with an agreed ceiling: you pay for actual hours, never more than the cap. The vendor carries the risk of overruns, and you get the upside if things go fast. Note that in practice the cap tends to function as a benchmark – don’t count on landing well under it.
- Target price sets a shared target sum and splits the deviation: if the project comes in cheaper, the gain is shared; if it costs more, the hit is shared according to an agreed split, for example 50/50. It’s the model that best turns the vendor into a partner in the budget.
- Phased fixed price locks a defined phase at a time to a fixed price, with renegotiation between phases. Good when the organization requires firm commitments but the project is too long for a single spec.
Controls you should require in a time-and-materials setup
Time and materials without governance is an open tap. Write the mechanisms into the contract:
- Weekly time reports by person and activity – not a lump sum at month-end.
- A demo of working product every sprint, so hours can always be measured against visible results.
- A budget cap with a warning threshold: written flagging when, for example, 75 percent of the budget is used, with a forecast for the rest.
- A backlog you own: the vendor proposes, you prioritize – every sprint.
- Short notice period, typically 30 days, so the collaboration is sustained by delivery rather than lock-in.
A vendor who sees these as reasonable terms has nothing to hide – that’s a good selection criterion in itself.
A worked example: the same project in two models
Say an app requires about 500 hours. Under time and materials at an hourly rate of SEK 1,100: SEK 550,000 if the estimate holds, more or less if it doesn’t. As a fixed price, the same project might be quoted at SEK 640,000 – the extra SEK 90,000 is the risk premium. If the spec holds exactly, you paid SEK 90,000 for insurance you didn’t need; if surprises worth SEK 200,000 show up, you made a good deal. Fixed price isn’t inherently more or less expensive than time and materials – it’s a bet on how much you don’t yet know. The better the preparatory work, the smaller the uncertainty, and the less valuable the insurance.
At Weapp, we work with all the models and recommend a form based on the project’s uncertainty – often a fixed price for a discovery phase followed by capped time and materials for development. Want a recommendation for your project? Get in touch.
Frequently asked questions
What is a risk premium in a fixed-price quote?
It's the vendor's buffer for everything that can go wrong: unclear requirements, technical surprises, changes. The premium is often 10–20 percent of the price and rarely shows up as its own line item. You pay it regardless of whether the risks materialize – it's the insurance premium for a fixed price.
What does a change order mean in a development project?
A change order covers changes and additional work – everything outside the agreed scope in a fixed-price project, and therefore priced separately. Many fixed-price projects end up costing more than the quote precisely because of the change-order list, so always ask for examples of how the vendor has handled changes before.
How do I know the hours on the invoice are accurate under time and materials?
Require time reports broken down by person and activity, delivered every week, and compare them against what the sprint demos actually show. The pattern over a few sprints tells you everything: hours that don't show up as working functionality should be explainable.
Can you switch pricing model mid-project?
Yes, at natural phase boundaries. A common setup is fixed price for the discovery phase, time and materials during development, and a fixed maintenance contract after launch. The model should reflect the uncertainty in each phase rather than stay the same throughout the journey.
Which model do development agencies themselves tend to prefer?
Most Swedish agencies prefer time and materials, often with a cap, since fixed price forces them to price uncertainty and defend scope boundaries. Serious vendors, however, offer both and recommend a model based on how clear the requirements actually are – be wary of one that only offers a single option.