diff --git a/static/bootstrap/stylesheets/bootstrap/mixins/_size.scss b/static/bootstrap/stylesheets/bootstrap/mixins/_size.scss
new file mode 100644
index 0000000000000000000000000000000000000000..abbe2463ce8d7c315f8a2368f9301603315a35db
--- /dev/null
+++ b/static/bootstrap/stylesheets/bootstrap/mixins/_size.scss
@@ -0,0 +1,10 @@
+// Sizing shortcuts
+
+@mixin size($width, $height) {
+  width: $width;
+  height: $height;
+}
+
+@mixin square($size) {
+  @include size($size, $size);
+}