diff --git a/util/metrics.py b/util/metrics.py
index a8a1d85e..55b1612a 100755
--- a/util/metrics.py
+++ b/util/metrics.py
@@ -1,5 +1,7 @@
 #!/usr/bin/env python
 
+from __future__ import print_function
+
 import glob
 import fnmatch
 import itertools
@@ -10,6 +12,9 @@ TODO_PATTERN = re.compile(r'\s*// TODO:')
 DOC_PATTERN = re.compile(r'\s*//')
 EXPECT_PATTERN = re.compile(r'// expect')
 
+C_FORMAT_LINE = "{0:<10}  {1:>7}  {2:>7}  {3:>7}  {4:>7}  {5:>7}  {6:>7}  {7:>7}"
+WREN_FORMAT_LINE = "{0:<10}  {1:>7}  {2:>7}  {3:>7}  {4:>7}  {5:>7}  {6:>7}"
+
 num_files = 0
 num_docs = 0
 num_code = 0
@@ -26,64 +31,94 @@ num_benchmark_todos = 0
 num_benchmark_empty = 0
 num_benchmark = 0
 
-files = itertools.chain(glob.iglob("src/vm/*.[ch]"),
-                        glob.iglob("src/include/*.[ch]"))
-for source_path in files:
-  num_files += 1
-  with open(source_path, "r") as input:
-    for line in input:
-      num_semicolons += line.count(';')
-      match = TODO_PATTERN.match(line)
-      if match:
-        num_todos += 1
-        continue
+def c_metrics(label, directories):
+  """Reports the metrics of one or more directories of C code."""
+  num_files = 0
+  num_semicolons = 0
+  num_todos = 0
+  num_code = 0
+  num_docs = 0
+  num_empty = 0
 
-      match = DOC_PATTERN.match(line)
-      if match:
-        num_docs += 1
-        continue
+  for directory in directories:
+    files = glob.iglob(directory + "/*.[ch]")
+    for source_path in files:
+      num_files += 1
 
-      stripped = line.strip()
-      # Don't count { or } lines since Wren's coding style puts them on their
-      # own lines but they don't add anything meaningful to the length of the
-      # program.
-      if (stripped == "" or stripped == "{" or stripped == "}"):
-        num_empty += 1
-        continue
+      with open(source_path, "r") as input:
+        for line in input:
+          num_semicolons += line.count(';')
+          match = TODO_PATTERN.match(line)
+          if match:
+            num_todos += 1
+            continue
 
-      num_code += 1
+          match = DOC_PATTERN.match(line)
+          if match:
+            num_docs += 1
+            continue
 
-for dir_path, dir_names, file_names in os.walk("test"):
-  for file_name in fnmatch.filter(file_names, "*.wren"):
-    num_test_files += 1
-    with open(os.path.join(dir_path, file_name), "r") as input:
-      for line in input:
-        if (line.strip() == ""):
-          num_test_empty += 1
-        else:
-          num_test += 1
+          stripped = line.strip()
+          # Don't count { or } lines since Wren's coding style puts them on
+          # their own lines but they don't add anything meaningful to the
+          # length of the program.
+          if stripped == "" or stripped == "{" or stripped == "}":
+            num_empty += 1
+            continue
 
-        match = TODO_PATTERN.match(line)
-        if match:
-          num_test_todos += 1
-          continue
+          num_code += 1
 
-        match = EXPECT_PATTERN.search(line)
-        if match:
-          num_expects += 1
-          continue
+  print(C_FORMAT_LINE.format(
+      label, num_files, num_semicolons, num_todos, num_code, num_docs,
+      num_empty, num_todos + num_docs + num_empty + num_code))
 
-print("source:")
-print("  files           " + str(num_files))
-print("  semicolons      " + str(num_semicolons))
-print("  TODOs           " + str(num_todos))
-print("  comment lines   " + str(num_docs))
-print("  code lines      " + str(num_code))
-print("  empty lines     " + str(num_empty))
-print("\n")
-print("test:")
-print("  files           " + str(num_test_files))
-print("  TODOs           " + str(num_test_todos))
-print("  expectations    " + str(num_expects))
-print("  non-empty lines " + str(num_test))
-print("  empty lines     " + str(num_test_empty))
+
+def wren_metrics(label, directories):
+  """Reports the metrics of one or more directories of Wren code."""
+  num_files = 0
+  num_empty = 0
+  num_code = 0
+  num_todos = 0
+  num_expects = 0
+
+  for directory in directories:
+    for dir_path, dir_names, file_names in os.walk(directory):
+      for file_name in fnmatch.filter(file_names, "*.wren"):
+        num_files += 1
+
+        with open(os.path.join(dir_path, file_name), "r") as input:
+          for line in input:
+            if line.strip() == "":
+              num_empty += 1
+              continue
+
+            match = TODO_PATTERN.match(line)
+            if match:
+              num_todos += 1
+              continue
+
+            match = EXPECT_PATTERN.search(line)
+            if match:
+              num_expects += 1
+              continue
+
+            num_code += 1
+
+  print(WREN_FORMAT_LINE.format(
+      label, num_files, num_todos, num_code, num_expects, num_empty,
+      num_todos + num_code + num_expects + num_empty))
+
+
+print(C_FORMAT_LINE.format(
+    "", "files", "';'", "todos", "code", "comment", "empty", "total"))
+c_metrics("vm",       ["src/vm", "src/include"])
+c_metrics("optional", ["src/optional"])
+c_metrics("cli",      ["src/cli", "src/module"])
+
+print()
+print(WREN_FORMAT_LINE.format(
+    "", "files", "todos", "code", "expects", "empty", "total"))
+wren_metrics("core",      ["src/vm"])
+wren_metrics("optional",  ["src/optional"])
+wren_metrics("cli",       ["src/module"])
+wren_metrics("test",      ["test"])