diff --git a/core/src/net/sf/openrocket/unit/UnitGroup.java b/core/src/net/sf/openrocket/unit/UnitGroup.java
index 090b5ec49..c79272a64 100644
--- a/core/src/net/sf/openrocket/unit/UnitGroup.java
+++ b/core/src/net/sf/openrocket/unit/UnitGroup.java
@@ -291,6 +291,7 @@ public class UnitGroup {
 		UNITS_ROUGHNESS = new UnitGroup();
 		UNITS_ROUGHNESS.addUnit(new GeneralUnit(0.000001, MICRO + "m"));
 		UNITS_ROUGHNESS.addUnit(new GeneralUnit(0.0000254, "mil"));
+		UNITS_ROUGHNESS.addUnit(new GeneralUnit(0.0254, "in"));
 		UNITS_ROUGHNESS.addUnit(new GeneralUnit(1, "m"));