diff --git a/CHANGES b/CHANGES
index e06a6faba..8789b53af 100644
--- a/CHANGES
+++ b/CHANGES
@@ -15,6 +15,9 @@ Deprecated
 Features added
 --------------
 
+* #4271: sphinx-build supports an option called ``-j auto`` to adjust numbers of
+  processes automatically.
+
 Bugs fixed
 ----------
 
diff --git a/doc/man/sphinx-build.rst b/doc/man/sphinx-build.rst
index 46f213989..fdd0d36c2 100644
--- a/doc/man/sphinx-build.rst
+++ b/doc/man/sphinx-build.rst
@@ -143,11 +143,15 @@ Options
 
    Distribute the build over *N* processes in parallel, to make building on
    multiprocessor machines more effective.  Note that not all parts and not all
-   builders of Sphinx can be parallelized.
+   builders of Sphinx can be parallelized.  If ``auto`` argument is given,
+   Sphinx uses the number of CPUs as *N*.
 
    .. versionadded:: 1.2
       This option should be considered *experimental*.
 
+   .. versionchanged:: 1.7
+      Support ``auto`` argument.
+
 .. option:: -c path
 
    Don't look for the :file:`conf.py` in the source directory, but use the given
diff --git a/sphinx/cmdline.py b/sphinx/cmdline.py
index 779ba142d..4cf5a07ef 100644
--- a/sphinx/cmdline.py
+++ b/sphinx/cmdline.py
@@ -11,6 +11,7 @@
 from __future__ import print_function
 
 import argparse
+import multiprocessing
 import sys
 import traceback
 from os import path
@@ -83,6 +84,23 @@ def handle_exception(app, args, exception, stderr=sys.stderr):
                   file=stderr)
 
 
+def jobs_argument(value):
+    # type: (str) -> int
+    """
+    Special type to handle 'auto' flags passed to 'sphinx-build' via -j flag. Can
+    be expanded to handle other special scaling requests, such as setting job count
+    to cpu_count.
+    """
+    if value == 'auto':
+        return multiprocessing.cpu_count()
+    else:
+        jobs = int(value)
+        if jobs <= 0:
+            raise argparse.ArgumentTypeError('job number should be a positive number')
+        else:
+            return jobs
+
+
 def get_parser():
     # type: () -> argparse.ArgumentParser
     parser = argparse.ArgumentParser(
@@ -129,10 +147,9 @@ files can be built by specifying individual filenames.
     group.add_argument('-d', metavar='PATH', dest='doctreedir',
                        help='path for the cached environment and doctree '
                        'files (default: OUTPUTDIR/.doctrees)')
-    group.add_argument('-j', metavar='N', default=1, type=int, dest='jobs',
+    group.add_argument('-j', metavar='N', default=1, type=jobs_argument, dest='jobs',
                        help='build in parallel with N processes where '
-                       'possible')
-
+                       'possible (special value "auto" will set N to cpu-count)')
     group = parser.add_argument_group('build configuration options')
     group.add_argument('-c', metavar='PATH', dest='confdir',
                        help='path where configuration file (conf.py) is '