diff --git a/.flake8 b/.flake8
@@ -5,7 +5,7 @@ exclude =
     build,
     dist,
     doc/source/conf.py
-max-line-length = 115
+max-line-length = 79
 # Ignore some style 'errors' produced while formatting by 'black'
 # https://black.readthedocs.io/en/stable/guides/using_black_with_other_tools.html#labels-why-pycodestyle-warnings
 extend-ignore = E203
diff --git a/.isort.cfg b/.isort.cfg
@@ -1,4 +1,4 @@
 [settings]
-line_length = 115
+line_length = 79
 multi_line_output = 3
 include_trailing_comma = True
diff --git a/doc/source/conf.py b/doc/source/conf.py
@@ -221,7 +221,13 @@
 # (source start file, target name, title,
 # author, documentclass [howto, manual, or own class]).
 latex_documents = [
-    ("index", "diffpy.utils.tex", "diffpy.utils Documentation", ab_authors, "manual"),
+    (
+        "index",
+        "diffpy.utils.tex",
+        "diffpy.utils Documentation",
+        ab_authors,
+        "manual",
+    ),
 ]
 
 # The name of an image file (relative to this directory) to place at the top of
@@ -249,7 +255,9 @@
 
 # One entry per manual page. List of tuples
 # (source start file, name, description, authors, manual section).
-man_pages = [("index", "diffpy.utils", "diffpy.utils Documentation", ab_authors, 1)]
+man_pages = [
+    ("index", "diffpy.utils", "diffpy.utils Documentation", ab_authors, 1)
+]
 
 # If true, show URL addresses after external links.
 # man_show_urls = False

diff --git a/news/linelength79.rst b/news/linelength79.rst
@@ -0,0 +1,23 @@
+**Added:**
+
+* update isort, flake8 and black to set line limit to 79
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>
diff --git a/pyproject.toml b/pyproject.toml
@@ -57,7 +57,7 @@ ignore-words = ".codespell/ignore_words.txt"
 skip = "*.cif,*.dat"
 
 [tool.black]
-line-length = 115
+line-length = 79
 include = '\.pyi?$'
 exclude = '''
 /(