diff --git a/README.md b/README.md
index 7ec661c..992795f 100644
--- a/README.md
+++ b/README.md
@@ -90,6 +90,12 @@ metrify you do not need to explicitly tell it the unit you are converting to,
 because due to its requirements (conversion is always from non-metric to metric)
 it can automatically pick the correct one.
 
+Why should I use units(1) instead of metrify?
+---------------------------------------------
+units(1) includes many more units than covered by metrify, in addition to
+allowing other conversions than non-metric to metric. It can also be used for
+calculations involving units, which metrify does not handle outside of addition.
+
 Building and installation
 -------------------------
 You can build and test out metrify with `cargo run`. If you want to install it