Use fixed fees only for well-defined scope
When it may fit: Overruns are common.
Evidence needed: Scope clarity and estimate-to-actual history.
Trade-off: Lose some fixed-fee work.
Professional Services Intelligence Brief
How to Compare Fixed-Fee and Time-Based Engagements
Fixed fees reward efficiency and punish overruns. Hourly billing is the reverse. Which one earns more depends on how well the firm scopes and controls its work.
1. The business problem
Do we earn more on fixed-fee work or on time-based work?
Clients often prefer fixed fees for certainty, and firms often like them for pricing on value. But a fixed fee shifts the risk of overruns to the firm. A project that takes more hours than estimated earns less per hour, sometimes less than cost.
Comparing the two models fairly means measuring effective realized rate per hour, not just fees collected.
2. What the evidence can reveal
A comparison looks at the same measures for both models:
- Calculated Effective revenue per hour: fees divided by hours actually worked.
- Calculated Hours estimated versus hours worked, for fixed-fee work.
- Calculated Write-downs on time-based work.
- Information gap Scope definition, change control and who bears the risk of client-driven changes.
The model that earns more is often the one the firm can control better.
3. Investigate the problem
Illustrative A simple illustration, with invented numbers: a fixed fee of $50,000 is priced for 200 hours at a standard $250 an hour. If the team works 260 hours, the effective rate is about $192 an hour, below the firm’s cost of roughly $198 an hour, so the engagement loses money. The same 260 hours billed by time at $250 would have been $65,000 before write-downs.
In the synthetic firm, Calculated realization slipped from 82.6% to 81.7% while utilization rose to 81.6%: more time was worked for each dollar collected. Technology consulting shows the effect in its sharpest form: hours grew 25.0%, revenue only 13.2%, and the realized rate fell from $190 to $172.
Hypothesis A drop in effective rate with growing hours is consistent with fixed-fee work that is overrunning its scope, though it could also reflect discounting. Information gap The demo does not tag engagements by fee model. The first step is to record the pricing basis of each engagement and compare effective rates between them.
4. Explore the interactive experience
Investigate it yourself.
Firm Economics Dashboard: a service-line dashboard with utilization and realization, a scenario simulator for hours, rate and cost, evidence-linked answers from APIS, and a sample brief, all on synthetic data.
The experience below is built on a synthetic firm, “Demo Advisory Partners,” analyzed by service line. It has no client-level or engagement-level records, so service lines are used to show the method. Nothing in it is real.
- Select Technology Consulting. Its hours grew far faster than its revenue. What might that mean for fees?
- In the Scenario tab, lower realized rate by 5%. This is the effect of a fixed fee overrunning.
- Ask APIS why a busy firm may have weak margins.
5. Evaluate possible solutions
The choice of fee model should follow scoping discipline.
6. What leadership should do next
Questions to answer
- What is the effective hourly rate on each model?
- How often do fixed-fee engagements overrun?
- Who bears scope-change risk?
- Which model fits each service?
Data to gather
- Pricing basis per engagement
- Hours estimated and worked
- Change history
- Write-downs
Steps to take
- Tag engagements by model.
- Compare effective rates.
- Adjust pricing and scope rules.
- Review quarterly.
7. Engage Two Pillars
Understand Your Firm’s Economics and Growth Opportunities
Two Pillars can help professional services firms investigate client profitability, engagement operations, capacity and strategic growth using your own data. A good first step is a fee-model comparison that shows the effective rate on fixed-fee versus time-based work.
Sources and data notes
- The organization, its figures, and every number in this article and its interactive experience are synthetic and illustrative. They are not real data, a benchmark, or a forecast.
- Reviewed October 2026. This article describes an approach to investigation. It does not replace review by qualified professionals.