Cell Viability Analyzer
A free online cell viability analyzer that fits 4-parameter logistic dose-response curves to calculate IC50/EC50 values, Hill slopes, and R² goodness of fit. Enter absorbance data from MTT, XTT, WST-1, or Alamar Blue assays with control normalization and blank subtraction — view interactive dose-response plots in your browser with no data uploaded.
Assay Type
Tetrazolium reduction assay; measures mitochondrial dehydrogenase activity via formazan crystal formation
Absorbance: 570 nm / 630 nm
Control Values (untreated)
Dose-Response Data
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What is a Cell Viability Analyzer?
A cell viability analyzer processes data from cytotoxicity assays (MTT, XTT, WST-1, Alamar Blue, SRB, LDH) to determine the dose-response relationship between a compound and cell survival. It normalizes raw absorbance data to control wells, fits a 4-parameter logistic curve, and calculates the IC50 — the concentration at which 50% of cells are inhibited. This is a fundamental measurement in pharmacology, toxicology, and drug discovery for evaluating compound potency.
How to Use This Analyzer
- Select your assay type (MTT, XTT, WST-1, etc.) for appropriate wavelength reference
- Enter absorbance values for each drug concentration (with replicates if available)
- Enter control (untreated) and blank (media only) absorbance values for normalization
- Click Analyze to fit the dose-response curve and calculate IC50
- View the dose-response plot showing % viability vs. concentration on a log scale
Frequently Asked Questions
What is IC50 and how is it different from EC50?
IC50 (half-maximal inhibitory concentration) is the drug concentration that inhibits 50% of cellular activity or viability. EC50 (half-maximal effective concentration) is the broader term for the concentration producing 50% of the maximum effect. IC50 is used when measuring inhibition (cytotoxicity), while EC50 applies to any dose-response relationship including activation. Both are calculated from the inflection point of the 4PL curve.
What does the Hill slope tell me?
The Hill slope (also called Hill coefficient) indicates the steepness of the dose-response curve. A Hill slope of -1 is typical for standard dose-response. Steeper slopes (< -1, e.g., -2 or -3) suggest cooperative binding or switch-like behavior. Shallower slopes (> -1, e.g., -0.5) suggest heterogeneous receptor populations or multiple mechanisms. The sign indicates direction: negative for inhibition, positive for activation.
Why is my IC50 showing an unusual value?
Unusual IC50 values can result from: (1) insufficient concentration range — your doses may not span the full S-curve, (2) poor plate quality — high variability between replicates, (3) non-monotonic data — viability increases then decreases, or (4) incomplete killing — bottom plateau doesn't reach 0%. Ensure your concentration range covers at least 10% to 90% viability, use at least 6-8 concentration points, and include proper controls.