ELISA Titer Calculator
Analyze ELISA results by calculating the sample-to-cutoff (S/CO) ratio and estimating antibody titer from optical density (OD) readings.
ELISA Titer Calculator
intermediateCalculate sample-to-cutoff ratio and estimate antibody titer
Formula
S/CO = Sample OD / Cutoff OD
Scenario A
How It Works
ELISA (Enzyme-Linked Immunosorbent Assay) uses optical density measurements to quantify antibodies or antigens. The cutoff OD is the threshold value that separates positive from negative results.
S/CO Ratio = Sample OD / Cutoff OD
Estimated Titer = S/CO × Dilution Factor
Interpretation: S/CO ≥ 1.0 = Positive; S/CO < 1.0 = Negative. The titer estimate indicates the approximate endpoint dilution of the sample.
Example
A serum sample diluted 1:100 gives OD = 1.2. The cutoff is OD = 0.4:
S/CO = 1.2 / 0.4 = 3.00 (Strong Positive)
Estimated Titer = 3.00 × 100 = 300
The sample is strongly positive with an estimated titer of 1:300.
Frequently Asked Questions
How is the cutoff OD determined?
The cutoff is typically calculated from negative control samples: Cutoff = Mean(negative ODs) + 3×Standard Deviation, or a fixed multiplier of the negative control mean (e.g., 2.1× for some commercial kits).
What is a gray zone in ELISA?
Many assays define a "gray zone" of borderline results, typically S/CO between 0.9-1.1. Samples in this range should be retested or confirmed with a different method.
What does the titer estimate represent?
The titer is the highest dilution at which the sample still gives a positive result. A titer of 300 means the sample could be diluted 300-fold and still be positive.
Save Configuration Snapshot
Save current parameters to your dashboard for instant one-click reloading.
About This Calculator & Guide
About the ELISA Titer Calculator
The ELISA Titer Calculator is a specialized online utility designed to help you calculate sample-to-cutoff (s/co) ratio and estimate antibody titer from elisa optical density readings. free online elisa analysis calculator. It performs calculations in real-time to provide immediate, reliable estimates for study, work, or daily tasks.
How to Use
Simply enter your parameters in the input fields of the calculator widget above. The tool evaluates the inputs instantly and displays the results in real-time. You can modify any value to check alternate scenarios and compare figures dynamically.
Data Privacy & Safety
All calculations are executed locally within your web browser. No inputs are sent to our servers or stored externally, ensuring your personal and financial details remain completely private and secure.
FAQ
Frequently Asked Questions
What does the ELISA Titer Calculator do?+
Calculate sample-to-cutoff (S/CO) ratio and estimate antibody titer from ELISA optical density readings. Free online ELISA analysis calculator. It is designed for quick everyday use and gives clear results without requiring a sign in.
Is the ELISA Titer Calculator free to use?+
Yes. The ELISA Titer Calculator is free to use online and works directly in your browser.
Can I use the ELISA Titer Calculator on mobile?+
Yes. The calculator layout is responsive, so you can use it on phones, tablets, laptops, and desktop screens.