MTT Assay Calculator
Enter each treatment group name and its absorbance reading.
| Sample / Treatment | OD Reading | |
|---|---|---|
Enter drug concentrations and corresponding viability percentages (or absorbance values with a control). IC50 is estimated by linear interpolation between the two concentrations bracketing 50% viability.
Enter concentration (µM or any unit) and OD or % viability for each dose.
| Concentration | OD or Viability % | |
|---|---|---|
MTT Assay Results
How to Use the MTT Assay Calculator
Select the tab matching your experiment. For Single Sample, enter the blank (media only), control (untreated cells), and sample (treated cells) OD values to get viability percentage with background correction. For Multi-Sample, enter one control OD and up to 10 treatment groups to compare viability across conditions with a bar chart. For IC50 Estimator, enter dose-response data points and the calculator interpolates the IC50 concentration.
MTT Assay Viability Formula
How the MTT Assay Works
MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) is a yellow tetrazolium salt reduced by metabolically active cells to purple formazan crystals. The amount of formazan produced is directly proportional to the number of viable, metabolically active cells. After dissolving the crystals in DMSO or isopropanol, the absorbance is read at 570 nm.
Assay Variants and Wavelengths
- MTT: Read at 570 nm (reference 630–690 nm). Requires DMSO solubilisation step.
- MTS / CellTiter 96: Read at 490 nm. Soluble formazan — no solubilisation needed.
- WST-1: Read at 450 nm (reference 600–690 nm). Soluble, highly sensitive.
- Resazurin / AlamarBlue: Fluorometric or absorbance at 570/600 nm. Non-toxic — can re-use cells.
Tips for Reliable MTT Results
- Always include a blank (media + MTT, no cells) to correct for background absorbance.
- Seed cells 24 hours before treatment to allow attachment and recovery from passaging.
- Use at least triplicate wells per condition — outliers are common in colorimetric assays.
- Ensure the solubilisation step is complete before reading — undissolved crystals give inaccurate OD values.
- Read the plate within 1 hour of adding DMSO — formazan crystals can re-precipitate over time.
- Drug compounds that are coloured or interfere with the tetrazolium reaction can cause false readings.