diff --git a/BUILD.md b/BUILD.md
index 1874e8dd8..c8a593b8a 100644
--- a/BUILD.md
+++ b/BUILD.md
@@ -152,6 +152,10 @@ Now that the build configuration has been set, run make, replacing `X` with the
 
     make -jX
 
+On Linux, `X` can be substituted with `$(grep -c ^processor /proc/cpuinfo)`, to automatically get the number of cpu threads:
+
+    make -j$(grep -c ^processor /proc/cpuinfo)
+
 The zetaglest binaries will be in the `build/` directory. Run
 `./zetaglest` to start the game.