diff --git a/readme.md b/readme.md
index 8871430..641783a 100644
--- a/readme.md
+++ b/readme.md
@@ -2707,6 +2707,7 @@ Linear rails with carriages.
 | Function | Description |
 |:--- |:--- |
 | ```carriage_screw_depth(type)``` | Carriage thread depth |
+| ```carriage_size(type)``` | Size of carriage |
 | ```rail_holes(type, length)``` | Number of holes in a rail given its ```length``` |
 | ```rail_screw_height(type, screw)``` | Position screw taking into account countersink into counterbored hole |
 | ```rail_travel(type, length)``` | How far the carriage can travel |
diff --git a/vitamins/rail.scad b/vitamins/rail.scad
index f84914e..d09049e 100644
--- a/vitamins/rail.scad
+++ b/vitamins/rail.scad
@@ -40,6 +40,7 @@ function carriage_length(type)       = type[0]; //! Overall length
 function carriage_block_length(type) = type[1]; //! Length of the metal part
 function carriage_width(type)        = type[2]; //! Width of carriage
 function carriage_height(type)       = type[3]; //! Height of carriage
+function carriage_size(type)         = [ type[1], type[2], type[3] ]; //! Size of carriage
 function carriage_clearance(type)    = type[4]; //! Gap under the carriage
 function carriage_pitch_x(type)      = type[5]; //! Screw hole x pitch
 function carriage_pitch_y(type)      = type[6]; //! Screw hole y pitch