diff --git a/synapse/config/stats.py b/synapse/config/stats.py
index b518a3ed9c..b18ddbd1fa 100644
--- a/synapse/config/stats.py
+++ b/synapse/config/stats.py
@@ -27,19 +27,16 @@ class StatsConfig(Config):
 
     def read_config(self, config, **kwargs):
         self.stats_enabled = True
-        self.stats_bucket_size = 86400
+        self.stats_bucket_size = 86400 * 1000
         self.stats_retention = sys.maxsize
         stats_config = config.get("stats", None)
         if stats_config:
             self.stats_enabled = stats_config.get("enabled", self.stats_enabled)
-            self.stats_bucket_size = (
-                self.parse_duration(stats_config.get("bucket_size", "1d")) / 1000
+            self.stats_bucket_size = self.parse_duration(
+                stats_config.get("bucket_size", "1d")
             )
-            self.stats_retention = (
-                self.parse_duration(
-                    stats_config.get("retention", "%ds" % (sys.maxsize,))
-                )
-                / 1000
+            self.stats_retention = self.parse_duration(
+                stats_config.get("retention", "%ds" % (sys.maxsize,))
             )
 
     def generate_config_section(self, config_dir_path, server_name, **kwargs):
diff --git a/synapse/storage/schema/delta/56/stats_separated1.sql b/synapse/storage/schema/delta/56/stats_separated1.sql
index 95daf8f53b..045b5ca013 100644
--- a/synapse/storage/schema/delta/56/stats_separated1.sql
+++ b/synapse/storage/schema/delta/56/stats_separated1.sql
@@ -84,7 +84,7 @@ CREATE TABLE IF NOT EXISTS room_stats_current (
 -- represents HISTORICAL room statistics for a room
 CREATE TABLE IF NOT EXISTS room_stats_historical (
     room_id TEXT NOT NULL,
-    -- These stats cover the time from (end_ts - bucket_size)...end_ts (in seconds).
+    -- These stats cover the time from (end_ts - bucket_size)...end_ts (in ms).
     -- Note that end_ts is quantised.
     end_ts BIGINT NOT NULL,
     bucket_size INT NOT NULL,
diff --git a/synapse/storage/stats.py b/synapse/storage/stats.py
index 650c0050cb..35fca1dc7b 100644
--- a/synapse/storage/stats.py
+++ b/synapse/storage/stats.py
@@ -64,7 +64,8 @@ class StatsStore(StateDeltasStore):
         Quantises a timestamp to be a multiple of the bucket size.
 
         Args:
-            ts (int): the timestamp to quantise, in seconds since the Unix Epoch
+            ts (int): the timestamp to quantise, in milliseconds since the Unix
+                Epoch
 
         Returns:
             int: a timestamp which