IC50 Calculator

What is IC50?

IC50 (half maximal inhibitory concentration) is the concentration of an inhibitor where the response is reduced by half. It's a measure of the potency of a substance in inhibiting a specific biological or biochemical function.

How to Use

1. Enter concentrations (usually log scale)
2. Enter response values (% inhibition or activity)
3. Add replicates for better accuracy
4. Click Calculate to fit the curve
5. View IC50 value and curve fit

Data Requirements

• At least 4 concentration points
• Include concentrations above and below IC50
• Use log-spaced concentrations
• Response values typically 0-100%
• Multiple replicates improve accuracy

Hill Slope Interpretation

• -1: Standard competitive inhibition
• < -1: Steep curve (cooperative binding)
• > -1: Shallow curve (multiple sites)
• Positive: Inverse agonist or stimulation

Applications

• Drug discovery and screening
• Enzyme inhibition studies
• Cell viability assays
• Receptor binding assays
• Toxicology studies

FAQ

Q: IC50 vs EC50?
A: IC50 measures inhibition, EC50 measures activation/effect.

Q: Why use log concentrations?
A: Log scale provides better curve fitting across wide concentration ranges.