Neutralization Titer Calculator

Turn assay readings into reliable neutralization titers fast. Handle percent, controls, and positive-well formats cleanly. Download summaries for notes, audits, and team sharing later.

Calculator
Two calculation tracks: percent neutralization (NTx) or Reed–Muench endpoint (IDx).
Tip: Use reciprocal dilution values (e.g., 160 for 1:160).
Common choices: 50 (NT50/ID50) or 90 (NT90/ID90).
Raw signal is converted to % neutralization.
Virus-only (0% neutralization).
Background (100% neutralization baseline).
Dilution series
Enter reciprocal dilution and input value for each row.
Dilution (reciprocal) Percent neutralization
Raw signal conversion: %N = 100 × [1 − (Sample − Cell) / (Virus − Cell)]
Positive / total table
Use wells, foci, plaques, or binary readouts.
Dilution (reciprocal) Positive Total
Reed–Muench builds cumulative positives and cumulative negatives, then interpolates in log dilution space.
Example data table
These examples demonstrate a typical serial dilution response.
Example: Percent neutralization
Dilution% Neutralization
1:2095
1:4088
1:8073
1:16052
1:32035
1:64015
Example: Positive/total (Reed–Muench)
DilutionPositiveTotal
1:1088
1:2078
1:4058
1:8038
1:16018
1:32008
Formula used
1) Percent neutralization from raw signal
Used when you provide sample signal values plus controls.
%N = 100 × [1 − (Sample − Cell) / (Virus − Cell)]
Where Virus is the virus-only control and Cell is the background control.
2) Log-linear endpoint interpolation (NTx)
Find two dilutions that bracket the endpoint, then interpolate in log10 dilution space.
log10(D*) = log10(D1) + (Endpoint − Y1) × (log10(D2) − log10(D1)) / (Y2 − Y1)
D* is the reciprocal dilution titer (e.g., 160), Y is % neutralization.
3) Reed–Muench endpoint (IDx)
Build cumulative positives and cumulative negatives, compute Reed–Muench % at each dilution, then interpolate in log10 space.
RM% = CumPos / (CumPos + CumNeg) × 100
How to use this calculator
  1. Select a calculation mode: percent neutralization (NTx) or Reed–Muench endpoint (IDx).
  2. Set the endpoint percentage (commonly 50 or 90) and choose rounding.
  3. Enter reciprocal dilution values (e.g., 160 for 1:160) in ascending order.
  4. For percent mode, provide percent neutralization or raw signals plus controls.
  5. Click Calculate to see results above the form, then export CSV or PDF.
Use consistent plate layouts and controls for comparability.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.