Clinical Trial Sample Size Calculator
Comprehensive power analysis for clinical trial design
Continuous
Dichotomous
Survival
Clustered
Longitudinal
Study Design
Power Triplet
Typically 0.05
Typically 0.80 or 0.90
Effect Size Parameters
Smallest clinically meaningful difference
From prior studies or pilot data
Allocation
k=1 for equal allocation (most efficient)
Study Design
Power Parameters
Proportion Parameters
Proportion in control group
Expected proportion in treatment group
Allocation
Study Design
Power Parameters
Note: This calculator assumes exponential survival (constant hazard) when converting required events to total sample size.
Hazard Parameters
HR < 1 favors treatment
Study Duration
Time to enroll all subjects
Minimum follow-up after last enrollment
For calculating event probabilities
Allocation
Outcome Type
Power Parameters
Effect Parameters (Continuous)
Cluster Parameters
Correlation within clusters (0-1)
Average number of subjects per cluster
Study Design
Power Parameters
Effect Parameters
Difference in slopes or means
Repeated Measures
Total assessments per subject
Between-measurement correlation