diff --git a/src/maps.rs b/src/maps.rs
index b7c24ef..1bda1a1 100644
--- a/src/maps.rs
+++ b/src/maps.rs
@@ -13,11 +13,17 @@ impl<V: Copy, T: Clone> VertexMap<V, T> {
         }
     }
 
-    // Reads beyond len() are valid and return the default value.
-    pub fn len(&self) -> usize {
-        self.inner.len()
+    // Reads beyond 'capacity' are valid and return the default value.
+    pub fn capacity(&self) -> usize {
+        self.inner.capacity()
     }
 
+    #[deprecated(since = "0.2.2", note = "use 'capacity' instead")]
+    pub fn len(&self) -> usize {
+        self.capacity()
+    }
+
+
     pub fn sync<G: GraphTopology<Vertex = V>>(&mut self, graph: &G) {
         self.inner.resize(graph.vertex_capacity());
     }
@@ -48,9 +54,14 @@ impl<E: Copy, T: Clone> EdgeMap<E, T> {
         }
     }
 
-    // Reads beyond len() are valid and return the default value.
+    // Reads beyond 'capacity' are valid and return the default value.
+    pub fn capacity(&self) -> usize {
+        self.inner.capacity()
+    }
+
+    #[deprecated(since = "0.2.2", note = "use 'capacity' instead")]
     pub fn len(&self) -> usize {
-        self.inner.len()
+        self.capacity()
     }
 
     pub fn sync<G: GraphTopology<Edge = E>>(&mut self, graph: &G) {
@@ -87,7 +98,7 @@ impl<E: Copy, T: Clone> EntityMap<E, T> {
         }
     }
 
-    pub fn len(&self) -> usize {
+    pub fn capacity(&self) -> usize {
         self.data.len()
     }
 
diff --git a/src/testing/maps_testing.rs b/src/testing/maps_testing.rs
index 202b2db..e8b5362 100644
--- a/src/testing/maps_testing.rs
+++ b/src/testing/maps_testing.rs
@@ -53,16 +53,16 @@ macro_rules! vertex_map_tests {
             let mut graph = <$T>::new();
             graph.add_vertex();
             let mut map = graph.vertex_map(42);
-            let initial_len = map.len();
-            while graph.vertex_capacity() <= initial_len {
+            let capacity_before = map.capacity();
+            while graph.vertex_capacity() <= capacity_before {
                 graph.add_vertex();
             }
             assert!(
-                map.len() < graph.vertex_capacity(),
+                map.capacity() < graph.vertex_capacity(),
                 "precondition: map is stale before sync"
             );
             map.sync(&graph);
-            assert_eq!(map.len(), graph.vertex_capacity());
+            assert_eq!(map.capacity(), graph.vertex_capacity());
         }
 
         #[test]
@@ -109,7 +109,7 @@ macro_rules! vertex_map_deletion_tests {
             let capacity_before = graph.vertex_capacity();
             graph.delete_vertex(v2);
             map.sync(&graph);
-            assert_eq!(map.len(), capacity_before);
+            assert_eq!(map.capacity(), capacity_before);
             assert_eq!(map[v1], 5);
         }
 
@@ -197,16 +197,16 @@ macro_rules! edge_map_tests {
             let v2 = graph.add_vertex();
             graph.add_edge(v1, v2);
             let mut map = graph.edge_map(42);
-            let initial_len = map.len();
-            while graph.edge_capacity() <= initial_len {
+            let capacity_before = map.capacity();
+            while graph.edge_capacity() <= capacity_before {
                 graph.add_edge(v1, v2);
             }
             assert!(
-                map.len() < graph.edge_capacity(),
+                map.capacity() < graph.edge_capacity(),
                 "precondition: map is stale before sync"
             );
             map.sync(&graph);
-            assert_eq!(map.len(), graph.edge_capacity());
+            assert_eq!(map.capacity(), graph.edge_capacity());
         }
 
         #[test]
@@ -259,7 +259,7 @@ macro_rules! edge_map_deletion_tests {
             let capacity_before = graph.edge_capacity();
             graph.delete_edge(e2);
             map.sync(&graph);
-            assert_eq!(map.len(), capacity_before);
+            assert_eq!(map.capacity(), capacity_before);
             assert_eq!(map[e1], 5);
         }