diff --git a/nemubot/tools/human.py b/nemubot/tools/human.py
index ef6f782..b751409 100644
--- a/nemubot/tools/human.py
+++ b/nemubot/tools/human.py
@@ -32,10 +32,9 @@ def size(size, unit=True):
     units = ['B','KiB','MiB','GiB','TiB','PiB','EiB','ZiB','YiB']
     p = math.floor(math.log(size, 2) / 10)
 
-    if unit:
-        return "%.3f %s" % (size / math.pow(1024,p), units[int(p)])
-    else:
-        return "%.3f" % (size / math.pow(1024,p))
+    s = size / math.pow(1024, p)
+    r = size % math.pow(1024, p)
+    return (("%.3f" if r else "%.0f") % s) + ((" " + units[int(p)]) if unit else "")
 
 
 def word_distance(str1, str2):
diff --git a/nemubot/tools/test_human.py b/nemubot/tools/test_human.py
index 00d2967..06b48d8 100644
--- a/nemubot/tools/test_human.py
+++ b/nemubot/tools/test_human.py
@@ -4,6 +4,23 @@ from nemubot.tools.human import size, word_distance
 
 class TestHuman(unittest.TestCase):
 
+    def test_size(self):
+        self.assertEqual(size(42), "42 B")
+        self.assertEqual(size(42, False), "42")
+        self.assertEqual(size(1023), "1023 B")
+        self.assertEqual(size(1024), "1 KiB")
+        self.assertEqual(size(1024, False), "1")
+        self.assertEqual(size(1025), "1.001 KiB")
+        self.assertEqual(size(1025, False), "1.001")
+        self.assertEqual(size(1024000), "1000 KiB")
+        self.assertEqual(size(1024000, False), "1000")
+        self.assertEqual(size(1024 * 1024), "1 MiB")
+        self.assertEqual(size(1024 * 1024, False), "1")
+        self.assertEqual(size(1024 * 1024 * 1024), "1 GiB")
+        self.assertEqual(size(1024 * 1024 * 1024, False), "1")
+        self.assertEqual(size(1024 * 1024 * 1024 * 1024), "1 TiB")
+        self.assertEqual(size(1024 * 1024 * 1024 * 1024, False), "1")
+
     def test_Levenshtein(self):
         self.assertEqual(word_distance("", "a"), 1)
         self.assertEqual(word_distance("a", ""), 1)