diff --git a/bumblebee_status/modules/core/disk.py b/bumblebee_status/modules/core/disk.py
index 12c7a16..ff0d4f9 100644
--- a/bumblebee_status/modules/core/disk.py
+++ b/bumblebee_status/modules/core/disk.py
@@ -8,6 +8,7 @@ Parameters:
     * disk.path: Path to calculate disk usage from (defaults to /)
     * disk.open: Which application / file manager to launch (default xdg-open)
     * disk.format: Format string, tags {path}, {used}, {left}, {size} and {percent} (defaults to '{path} {used}/{size} ({percent:05.02f}%)')
+    * disk.system: Unit system to use - SI (KB, MB, ...) or IEC (KiB, MiB, ...) (defaults to 'IEC')
 """
 
 import os
@@ -25,6 +26,7 @@ class Module(core.module.Module):
 
         self._path = self.parameter("path", "/")
         self._format = self.parameter("format", "{used}/{size} ({percent:05.02f}%)")
+        self._system = self.parameter("system", "IEC")
 
         self._used = 0
         self._left = 0
@@ -38,9 +40,9 @@ class Module(core.module.Module):
         )
 
     def diskspace(self, widget):
-        used_str = util.format.byte(self._used)
-        size_str = util.format.byte(self._size)
-        left_str = util.format.byte(self._left)
+        used_str = util.format.byte(self._used, sys=self._system)
+        size_str = util.format.byte(self._size, sys=self._system)
+        left_str = util.format.byte(self._left, sys=self._system)
         percent_str = self._percent
 
         return self._format.format(
diff --git a/bumblebee_status/util/format.py b/bumblebee_status/util/format.py
index 65242a3..3acf440 100644
--- a/bumblebee_status/util/format.py
+++ b/bumblebee_status/util/format.py
@@ -71,22 +71,33 @@ def astemperature(val, unit="metric"):
     return "{}°{}".format(int(val), __UNITS.get(unit.lower(), __UNITS["default"]))
 
 
-def byte(val, fmt="{:.2f}"):
+def byte(val, fmt="{:.2f}", sys="IEC"):
     """Returns a byte representation of the input value
 
     :param val: value to format, must be convertible into a float
     :param fmt: optional output format string, defaults to {:.2f}
+    :param sys: optional unit system specifier - SI (kilo, Mega, Giga, ...) or
+        IEC (kibi, Mebi, Gibi, ...) - defaults to IEC
 
     :return: byte representation (e.g. <X> KiB, GiB, etc.) of the input value
     :rtype: string
     """
 
+    if sys == "IEC":
+        div = 1024.0
+        units = ["", "Ki", "Mi", "Gi", "Ti"]
+        final = "TiB"
+    elif sys == "SI":
+        div = 1000.0
+        units = ["", "K", "M", "G", "T"]
+        final = "TB"
+
     val = float(val)
-    for unit in ["", "Ki", "Mi", "Gi"]:
-        if val < 1024.0:
+    for unit in units:
+        if val < div:
             return "{}{}B".format(fmt, unit).format(val)
-        val /= 1024.0
-    return "{}GiB".format(fmt).format(val * 1024.0)
+        val /= div
+    return "{}{}".format(fmt).format(val * div, final)
 
 
 __seconds_pattern = re.compile(r"(([\d\.?]+)h)?(([\d\.]+)m)?([\d\.]+)?s?")