diff --git a/pyproject.toml b/pyproject.toml
index 3e14cec..f661e52 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -29,9 +29,9 @@ dependencies = [
   "mammoth",
   "markdownify",
   "numpy",
+  "python-calamine",
   "python-pptx",
   "pandas",
-  "openpyxl",
   "pdfminer.six",
   "puremagic",
   "pydub",
diff --git a/src/markitdown/_markitdown.py b/src/markitdown/_markitdown.py
index 789c1e5..b0a6c75 100644
--- a/src/markitdown/_markitdown.py
+++ b/src/markitdown/_markitdown.py
@@ -713,18 +713,18 @@ class DocxConverter(HtmlConverter):
         return result
 
 
-class XlsxConverter(HtmlConverter):
+class ExcelConverter(HtmlConverter):
     """
-    Converts XLSX files to Markdown, with each sheet presented as a separate Markdown table.
+    Converts excel files to Markdown, with each sheet presented as a separate Markdown table.
     """
 
     def convert(self, local_path, **kwargs) -> Union[None, DocumentConverterResult]:
         # Bail if not a XLSX
         extension = kwargs.get("file_extension", "")
-        if extension.lower() != ".xlsx":
+        if extension.lower() not in [".xlsx", ".xls", ".xlsm", ".xlsb"]:
             return None
 
-        sheets = pd.read_excel(local_path, sheet_name=None)
+        sheets = pd.read_excel(local_path, sheet_name=None, engine="calamine")
         md_content = ""
         for s in sheets:
             md_content += f"## {s}\n"
@@ -1277,7 +1277,7 @@ class MarkItDown:
         self.register_page_converter(YouTubeConverter())
         self.register_page_converter(BingSerpConverter())
         self.register_page_converter(DocxConverter())
-        self.register_page_converter(XlsxConverter())
+        self.register_page_converter(ExcelConverter())
         self.register_page_converter(PptxConverter())
         self.register_page_converter(WavConverter())
         self.register_page_converter(Mp3Converter())
diff --git a/tests/test_files/test.xls b/tests/test_files/test.xls
new file mode 100644
index 0000000..f45bc98
Binary files /dev/null and b/tests/test_files/test.xls differ
diff --git a/tests/test_files/test.xlsb b/tests/test_files/test.xlsb
new file mode 100644
index 0000000..c002872
Binary files /dev/null and b/tests/test_files/test.xlsb differ
diff --git a/tests/test_files/test.xlsm b/tests/test_files/test.xlsm
new file mode 100644
index 0000000..01fff3d
Binary files /dev/null and b/tests/test_files/test.xlsm differ
diff --git a/tests/test_markitdown.py b/tests/test_markitdown.py
index 4a981bd..c6f1406 100644
--- a/tests/test_markitdown.py
+++ b/tests/test_markitdown.py
@@ -48,7 +48,7 @@ YOUTUBE_TEST_STRINGS = [
     "the model we're going to be using today is GPT 3.5 turbo",  # From the transcript
 ]
 
-XLSX_TEST_STRINGS = [
+EXCEL_TEST_STRINGS = [
     "## 09060124-b5e7-4717-9d07-3c046eb",
     "6ff4173b-42a5-4784-9b19-f49caff4d93d",
     "affc7dad-52dc-4b98-9b5d-51e65d8a8ad0",
@@ -174,7 +174,19 @@ def test_markitdown_local() -> None:
 
     # Test XLSX processing
     result = markitdown.convert(os.path.join(TEST_FILES_DIR, "test.xlsx"))
-    validate_strings(result, XLSX_TEST_STRINGS)
+    validate_strings(result, EXCEL_TEST_STRINGS)
+
+    # Test XLS processing
+    result = markitdown.convert(os.path.join(TEST_FILES_DIR, "test.xls"))
+    validate_strings(result, EXCEL_TEST_STRINGS)
+
+    # Test XLSM processing
+    result = markitdown.convert(os.path.join(TEST_FILES_DIR, "test.xlsm"))
+    validate_strings(result, EXCEL_TEST_STRINGS)
+
+    # Test XLSB processing
+    result = markitdown.convert(os.path.join(TEST_FILES_DIR, "test.xlsb"))
+    validate_strings(result, EXCEL_TEST_STRINGS)
 
     # Test DOCX processing
     result = markitdown.convert(os.path.join(TEST_FILES_DIR, "test.docx"))
@@ -206,7 +218,7 @@ def test_markitdown_local() -> None:
 
     # Test ZIP file processing
     result = markitdown.convert(os.path.join(TEST_FILES_DIR, "test_files.zip"))
-    validate_strings(result, XLSX_TEST_STRINGS)
+    validate_strings(result, EXCEL_TEST_STRINGS)
 
     # Test Wikipedia processing
     result = markitdown.convert(