diff --git a/src/fsutil/converters.py b/src/fsutil/converters.py
index 2399269..c83f199 100644
--- a/src/fsutil/converters.py
+++ b/src/fsutil/converters.py
@@ -11,7 +11,7 @@ def convert_size_bytes_to_string(size: int) -> str:
     units = SIZE_UNITS
     factor = 0
     factor_limit = len(units) - 1
-    while (size_num >= 1024) and (factor <= factor_limit):
+    while (size_num >= 1024) and (factor < factor_limit):
         size_num /= 1024
         factor += 1
     size_units = units[factor]
diff --git a/tests/test_converters.py b/tests/test_converters.py
index f7e95f1..3518cca 100644
--- a/tests/test_converters.py
+++ b/tests/test_converters.py
@@ -13,6 +13,9 @@
         (1073741824, "1.00 GB"),
         (1879048192, "1.75 GB"),
         (1099511627776, "1.00 TB"),
+        (2**80, "1.00 YB"),
+        (2**90, "1024.00 YB"),
+        (2**100, "1048576.00 YB"),
     ],
 )
 def test_convert_size_bytes_to_string(size_bytes, expected_output):
@@ -51,6 +54,9 @@ def test_convert_size_bytes_to_string_and_convert_size_string_to_bytes(
         ("1.00 MB", 1048576),
         ("1.00 GB", 1073741824),
         ("1.00 TB", 1099511627776),
+        ("1.00 YB", 2**80),
+        ("1024.00 YB", 2**90),
+        ("1048576.00 YB", 2**100),
     ],
 )
 def test_convert_size_string_to_bytes(size_string, expected_output):
@@ -69,6 +75,9 @@ def test_convert_size_string_to_bytes(size_string, expected_output):
         (1170378588, 1170378588),
         (2136746229, 2136746229),
         (1099511627776, 1099511627776),
+        (2**80, 2**80),
+        (2**90, 2**90),
+        (2**100, 2**100),
     ],
 )
 def test_convert_size_string_to_bytes_and_convert_size_bytes_to_string(