# Intraclass Correlation (ICC) Calculator

> Free ICC calculator. Paste the ratings of several raters and get ICC(1,1), ICC(2,1), ICC(3,1) and the mean-of-raters forms with 95% confidence intervals, a sentence for your manuscript and R code. Runs in your browser.

Canonical: https://biostatkit.com/icc

Paste the ratings (one row per subject, one column per rater) and get the intraclass correlation coefficient with its 95% confidence interval, all six forms in one table, a sentence you can paste into your manuscript, and the R code that reproduces the numbers.

## Methods wording

Reliability was calculated with BiostatKit [1] as the intraclass correlation coefficient [2], using the form named in the results, with the 95% CI from the F distribution.

Method: intraclass correlation, six Shrout-Fleiss forms, 95% CI from the F distribution (Shrout and Fleiss; McGraw and Wong).

## Frequently asked questions

### Which ICC should I use?

If different raters rated different subjects use one-way. If the same raters rated everyone and you want the result to hold for other raters too, use two-way random with absolute agreement. If only these raters matter, use two-way mixed with consistency. Then pick single rater or mean of raters according to how the scores will be used.

### What is a good ICC?

Koo and Li suggested below 0.50 poor, 0.50 to 0.75 moderate, 0.75 to 0.90 good and above 0.90 excellent, read from the 95% confidence interval. Judge the lower limit against what your field needs.

### Why is my interval so wide, or even below zero?

With few subjects the F-based interval is wide, and a lower limit below zero means the data cannot rule out agreement no better than chance. More subjects narrow it.

### ICC, kappa or Bland-Altman?

Use the ICC for numeric ratings by two or more raters, Cohen's kappa for categories, and a Bland-Altman analysis to show how far two measurement methods differ in the original units.

### Is my data stored or sent anywhere?

No. All calculations run in your browser tab. Nothing is uploaded, and the page works offline once loaded.

## Related calculators

- [Cohen's kappa](https://biostatkit.com/cohens-kappa)
- [Bland-Altman analysis](https://biostatkit.com/bland-altman)

Author: TS.BS. Vũ Duy Kiên (https://www.vuduykien.com)