diff --git a/.gitignore b/.gitignore
index ae05cdb..e7d00bc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,6 @@
 /venv/
 /.idea/
 /test_pypi_token.txt
+ms_reader/__pycache__/
+ms_reader.egg-info/
+tests/__pycache__/
\ No newline at end of file
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 08d459c..879e6fd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # Changelog
 
+## [1.9.0] - 2026-05-27
+
+### Addition
+
+Added a "R Squared" column in the calibration tab of the output file, taken directly from the Skyline input file.
+
+# Changelog
+
 ## [1.8.1] - 2026-02-02
 
 ### Changed
diff --git a/ms_reader/__init__.py b/ms_reader/__init__.py
index 2d986fc..0a0a43a 100644
--- a/ms_reader/__init__.py
+++ b/ms_reader/__init__.py
@@ -1 +1 @@
-__version__ = "1.8.1"
+__version__ = "1.9.0"
diff --git a/ms_reader/extract.py b/ms_reader/extract.py
index af083f9..9b0e296 100644
--- a/ms_reader/extract.py
+++ b/ms_reader/extract.py
@@ -65,7 +65,7 @@ def __init__(self, data, calrep=None, metadata=None, met_class="CM"):
         columns = [
             "Compound", "Sample_Name", "Area", "Response Ratio", "Sample Type",
             "Calculated Amt", "Theoretical Amt",
-            "Excluded", "%Diff"
+            "Excluded", "%Diff", "R Squared"
         ]
         self.data = self.data[columns].copy()
         self._replace_nf()
@@ -379,6 +379,7 @@ def _generate_minmax_calib(self):
             {"min": "LLOQ", "max": "ULOQ"},
             axis=1
         )
+        min_max_calib["R Squared"] = self.calib_data.groupby("Compound")["R Squared"].first()
         self.calib_data = min_max_calib
         self.excel_tables.append(
             ("Calibration", self.calib_data)