diff --git a/docs/usage.rst b/docs/usage.rst
index 731efc26f..30e6f0914 100644
--- a/docs/usage.rst
+++ b/docs/usage.rst
@@ -134,6 +134,19 @@ Network:
 In case you are interested in more details, please read the internals documentation.
 
 
+Units
+-----
+
+To display quantities, |project_name| takes care of respecting the
+usual conventions of scale. Disk sizes are displayed in `decimal
+<https://en.wikipedia.org/wiki/Decimal>`_, using powers of ten (so
+``kB`` means 1000 bytes). For memory usage, `binary prefixes
+<https://en.wikipedia.org/wiki/Binary_prefix>`_ are used, and are
+indicated using the `IEC binary prefixes
+<https://en.wikipedia.org/wiki/IEC_80000-13#Prefixes_for_binary_multiples>`_,
+using powers of two (so ``KiB`` means 1024 bytes).
+
+
 .. include:: usage/init.rst.inc
 
 Examples