Introduction

In the fast-paced world of software development, accurate project estimation and scope management are critical. Yet, many teams struggle with subjective metrics like story points or volatile technical measures. Enter Function Points (FP) and Simple Function Points (SFP): two ISO-standardized methods for quantifying software functional size from the user’s perspective.

Our latest research, based on 32,000+ anonymized measurements from FATTO’s MESUR platform, reveals a near-perfect correlation (96% R²) between FP and SFP—proving they measure the same underlying reality, just on different scales.

Key Takeaways

  1. FP vs. SFP: What’s the Difference?

    • FP (Function Points): Detailed, granular sizing (ISO/IEC 20926) that accounts for complexity. Ideal for precise estimation.

    • SFP (Simple Function Points): Streamlined for agility (ISO-compliant), focusing only on elementary processes and logical files. Perfect for early-stage or agile projects.

  2. The Conversion Factor
    Our linear regression model shows:

    FP≈1.03×SFP

    This means teams can seamlessly convert SFP to FP with minimal error (RMSE = 6.04).

  3. Why This Matters

    • Flexibility: Use SFP for speed, FP for rigor—with confidence they align.

    • Governance: MESUR platform leverages this relationship to enhance estimation, benchmarking, and agile scope control.

Visualizing the Data

 


*Figure 1: Strong linear relationship between FP and SFP (95% confidence interval). Source: MESUR dataset (n=28,292).*

Practical Applications

  • Agile Teams: Size user stories faster with SFP, then convert to FP for cross-team benchmarking.

  • Enterprise IT: Use FP for contractual compliance, but validate with SFP for internal tracking.

  • Tooling: Platforms like MESUR automate conversions, reducing manual effort.

Conclusion

Whether you prioritize detail (FP) or speed (SFP), standardized functional sizing is the key to transparent, data-driven development. The validated FP-SFP relationship means you no longer have to choose—you can use both strategically.

Ready to implement FP or SFP? Explore MESUR’s tools or dive into our full study for actionable insights!

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