diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index 85ce6bea1..f3a362db2 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -52,6 +52,15 @@ persist_event_counter = metrics.register_counter("persisted_events")
 event_counter = metrics.register_counter(
     "persisted_events_sep", labels=["type", "origin_type", "origin_entity"]
 )
+state_delta_counter = metrics.register_counter(
+    "state_delta",
+)
+state_delta_single_event_counter = metrics.register_counter(
+    "state_delta_single_event",
+)
+state_delta_reuse_delta_counter = metrics.register_counter(
+    "state_delta_reuse_delta",
+)
 
 
 def encode_json(json_object):
@@ -368,7 +377,8 @@ class EventsStore(EventsWorkerStore):
                                 room_id, ev_ctx_rm, latest_event_ids
                             )
 
-                            if new_latest_event_ids == set(latest_event_ids):
+                            latest_event_ids = set(latest_event_ids)
+                            if new_latest_event_ids == latest_event_ids:
                                 # No change in extremities, so no change in state
                                 continue
 
@@ -389,6 +399,25 @@ class EventsStore(EventsWorkerStore):
                                 if all_single_prev_not_state:
                                     continue
 
+                            state_delta_counter.inc()
+                            if len(new_latest_event_ids) == 1:
+                                state_delta_single_event_counter.inc()
+
+                                # This is a fairly handwavey check to see if we could
+                                # have guessed what the delta would have been when
+                                # processing one of these events.
+                                # What we're interested in is if the latest extremities
+                                # were the same when we created the event as they are
+                                # now. We guess this by looking at the prev events and
+                                # checking if they match up, as when this server creates
+                                # a new event it will use the extremities as the prev
+                                # events.
+                                for ev, _ in ev_ctx_rm:
+                                    prev_event_ids = set(e for e, _ in ev.prev_events)
+                                    if latest_event_ids == prev_event_ids:
+                                        state_delta_reuse_delta_counter.inc()
+                                    break
+
                             logger.info(
                                 "Calculating state delta for room %s", room_id,
                             )