IC50 Calculator

Estimate IC50 from dose-response data quickly; ideal for researchers, students, and lab professionals assessing inhibitor potency.

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About This Tool

The IC50 Calculator analyzes dose-response data by fitting a sigmoidal model to observed concentrations and responses. It reports potency (IC50), slope (Hill), and asymptotes, along with fit quality measures. The tool accommodates common assay formats and units, ensuring reproducible results.
Conceptually, it performs non-linear optimization to minimize residuals between observed responses and the model predictions. The core model is y = Bottom + (Top - Bottom)/(1 + (x/IC50)^Hill). IC50 corresponds to the midpoint between Top and Bottom; Hill determines curve steepness.
Benefits include rapid derivation of potency metrics, consistency across experiments, and easy export for reports. It is suitable for pharmacology, biochemistry, and medicinal chemistry workflows, including assay development, literature data validation, and regulatory documentation.

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How to Use

Provide inputs: supply concentration and response arrays with numeric values and specify concentration units if not inferred.
Choose model: select 4PL or Hill; optionally fix Top and Bottom or set constraints.
Run calculation: perform non-linear least squares fitting to estimate IC50, Hill slope, Top and Bottom, plus fit metrics.
Review outputs: inspect the IC50 value, confidence intervals, and goodness-of-fit indicators; check residuals for systematic patterns.
Export results: download a CSV or JSON report for reporting and record-keeping.

Frequently Asked Questions

Find Quick Answers

What is IC50?

IC50 is the concentration of an inhibitor where 50% of the biological activity is inhibited; it reflects potency. Lower IC50 indicates higher potency, but values depend on assay conditions and measurement scale.

What data formats are supported?

Inputs can be pasted as two numeric arrays or uploaded as CSV with columns for concentration and response. Inline arrays are accepted; concentrations should be numeric and may include units; responses can be percent or normalized values.

What models are available?

The tool fits a four-parameter logistic (4PL) or Hill-based model, with optional constraints on Top/Bottom. Non-linear fitting is used by default, though linearized options may be available for specific datasets.

How should results be interpreted?

IC50 is reported with its unit; the Hill slope indicates curve steepness. Confidence intervals reflect data variability. Use IC50 alongside Top/Bottom estimates to compare inhibitors across assays with attention to assay conditions and data quality.

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