Business Model Fit
Assesses whether the business model can sustainably support the product and market it serves.
About this assessment
Business Model Fit is the third and final stage of the ProductBooks evaluation framework. It determines whether your unit economics are real, whether costs scale predictably with growth, and whether revenue persists without being re-created through repeated sales effort. This is the stage where many funded startups fail: they scale a product with users but without sustainable economics. This evaluator prevents that mistake.
Evaluators apply strict evidence definitions.
Evidence that does not meet the definitions scores zero.
Typical flow
- 1Evaluate
- 2Identify missing evidence
- 3Generate evidence via operators
- 4Re-evaluate
Optional overview (3 min)
When to use this assessment
Use the Business Model Fit evaluator when you are approaching decisions about scaling, fundraising, or significant spend. This assessment ensures your economic model is validated by real data before committing.
- Before raising capital or presenting economics to investors
- When scaling spend and need to confirm unit economics hold under growth
- When the founder is heavily involved in revenue generation and delivery
Evaluation scope
Decides
Whether unit economics support sustainable operation
Does not do
Validate pricing strategy
Decides
Whether costs scale predictably with growth
Does not do
Optimise margins
Decides
Whether revenue durability exists independent of growth tactics
Does not do
Help you "pass"
| This evaluator decides | This evaluator does not do |
|---|---|
| Whether unit economics support sustainable operation | Validate pricing strategy |
| Whether costs scale predictably with growth | Optimise margins |
| Whether revenue durability exists independent of growth tactics | Help you "pass" |
Evidence requirements
- Unit economics must be observed, not projected
- Contribution margin must be positive or explainable
- Cost structure must be stable under growth
- Revenue durability must not depend on incentives
- Missing evidence scores zero
How missing evidence is generated
If required evidence is missing, ProductBooks uses controlled operators to generate it.
Operators generate evidence. They do not decide fit.
Unit Economics Reality Operator
Generates scoreable unit economics evidence by determining whether each customer produces positive contribution margin using observed data only.
Run operatorCAC Traceability Operator
Generates scoreable acquisition cost evidence by determining whether customer acquisition cost can be traced to specific customers and acquisition actions.
Run operatorRevenue Durability Operator
Generates scoreable revenue evidence by determining whether revenue persists over time without being re-created through repeated sales effort.
Run operatorCost Scaling Integrity Operator
Generates scoreable cost structure evidence by determining how costs change as revenue grows and whether margins hold or degrade.
Run operatorFounder Dependency & Load Operator
Generates scoreable operational risk evidence by determining whether core revenue generation or delivery depends on the founder's direct involvement.
Run operatorInterpreting your results
A high Business Model Fit score means your unit economics are based on observed data, your costs scale predictably, and your revenue persists independent of incentives or repeated sales effort. A low score does not mean the business is failing. It means the economic evidence is not yet sufficient to justify scaling.
Pay particular attention to the Founder Dependency operator. Many early-stage companies appear economically healthy because the founder personally drives revenue. This evaluator distinguishes between founder-dependent and system-dependent economics.
Related assessments
Business Model Fit is the final stage of the ProductBooks cascade. It is preceded by Product-Market Fit, which validates that users adopt and retain, and Problem-Solution Fit, which validates the underlying problem and solution.
Once all three stages are complete, use the Fit Report Generator to produce a comprehensive, investor-grade summary.
Learn more about the risk of founder dependency in our article on founder dependency risk.
Evaluator contract: This evaluator applies definitions strictly. Disputes do not change scoring.