diff --git a/libs/geom/include/psemek/geom/box.hpp b/libs/geom/include/psemek/geom/box.hpp
index 636d1165..410dd52a 100644
--- a/libs/geom/include/psemek/geom/box.hpp
+++ b/libs/geom/include/psemek/geom/box.hpp
@@ -230,4 +230,20 @@ namespace psemek::geom
 		return os;
 	}
 
+	template <typename T, std::size_t N>
+	box<T, N> expand(box<T, N> b, T const & d)
+	{
+		for (std::size_t i = 0; i < N; ++i)
+		{
+			b[i] = expand(b[i], d);
+		}
+		return b;
+	}
+
+	template <typename T, std::size_t N>
+	box<T, N> shrink(box<T, N> b, T const & d)
+	{
+		return expand(b, -d);
+	}
+
 }
diff --git a/libs/geom/include/psemek/geom/interval.hpp b/libs/geom/include/psemek/geom/interval.hpp
index 3bca9521..79f89af3 100644
--- a/libs/geom/include/psemek/geom/interval.hpp
+++ b/libs/geom/include/psemek/geom/interval.hpp
@@ -245,4 +245,16 @@ namespace psemek::geom
 		return os;
 	}
 
+	template <typename T>
+	interval<T> expand(interval<T> const & i, T const & d)
+	{
+		return {i.min - d, i.max + d};
+	}
+
+	template <typename T>
+	interval<T> shrink(interval<T> const & i, T const & d)
+	{
+		return expand(i, -d);
+	}
+
 }