Dissolution Testing

Dissolution Similarity Factor (f2) Calculator

Compare a test dissolution profile against a reference profile using the f2 similarity factor — commonly used to support formulation/process changes, scale-up, and biowaiver justifications.

What Is the f2 Similarity Factor?

The f2 similarity factor is a widely used statistic (per FDA and EMA guidance) for comparing two dissolution profiles — typically a reference (pre-change) and test (post-change) product — to determine whether they can be considered similar.

f2 = 50 × log10{ [1 + (1/n) × Σ(Rt − Tt)²]^-0.5 × 100 } Where: n = number of time points Rt = % dissolved of reference at time t Tt = % dissolved of test at time t

Acceptance Criterion

f2 Value	Interpretation
50 – 100	Profiles considered similar
< 50	Profiles considered dissimilar

Key Conditions for Valid Use (per FDA/EMA Guidance)

• Minimum of 3 time points (excluding time zero), with the first time point not exceeding 15 minutes
• Only one measurement should be included after 85% dissolution for either product
• %RSD at earlier time points should not exceed 20%, and at later time points should not exceed 10%
• Mean dissolution values should be used, based on data from 12 units per product

Interactive Calculator

Time Point	Reference % Dissolved	Test % Dissolved

f2 Similarity Factor

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This tool performs the f2 calculation for educational and preliminary assessment purposes. Confirm your dataset meets all FDA/EMA validity conditions (timepoint spacing, %RSD limits, single post-85% point, 12-unit means) before using f2 results to support a regulatory conclusion or biowaiver justification.