diff --git a/changelog.md b/changelog.md
index 5c99f92..8851d4e 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,6 @@
+* 4.0.3
+  - Added the `[wolff, queuing_bytes]` telemetry event which reports the amount of RAM/disk used by producer queues.
+
 * 4.0.2
   - Fix dynamic topic producer initialization failure handling (introduced in 3.0.0).
   - Fix `unexpected_id` crash when replayq overflow (introduced in 4.0.1).
diff --git a/src/wolff_metrics.erl b/src/wolff_metrics.erl
index 6afdd02..3f3443d 100644
--- a/src/wolff_metrics.erl
+++ b/src/wolff_metrics.erl
@@ -4,6 +4,7 @@
 -export([
     inflight_set/2,
     queuing_set/2,
+    queuing_bytes_set/2,
     dropped_inc/1,
     dropped_inc/2,
     dropped_queue_full_inc/1,
@@ -29,6 +30,12 @@ queuing_set(Config, Val) ->
                       #{gauge_set => Val},
                       telemetry_meta_data(Config)).
 
+%% @doc Number of bytes (RAM and/or disk) currently queuing. [Gauge]
+queuing_bytes_set(Config, Val) ->
+    telemetry:execute([wolff, queuing_bytes],
+                      #{gauge_set => Val},
+                      telemetry_meta_data(Config)).
+
 %% @doc Count of messages that were sent asynchronously but ACKs are not
 %% received. [Gauge]
 inflight_set(Config, Val) ->
diff --git a/src/wolff_producer.erl b/src/wolff_producer.erl
index adaaedd..af1ae60 100644
--- a/src/wolff_producer.erl
+++ b/src/wolff_producer.erl
@@ -275,6 +275,7 @@ do_init(#{client_id := ClientId,
   Config2 = resolve_max_linger_bytes(Config1, Q),
   Config = maps:without([replayq_dir, replayq_seg_bytes], Config2),
   wolff_metrics:queuing_set(Config, replayq:count(Q)),
+  wolff_metrics:queuing_bytes_set(Config, replayq:bytes(Q)),
   wolff_metrics:inflight_set(Config, 0),
   St#{replayq => Q,
       config := Config,
@@ -376,9 +377,11 @@ clear_gauges(#{config := Config}, Q) ->
 maybe_reset_queuing(Config, Q) ->
   case {replayq:count(Q), is_replayq_durable(Config, Q)} of
     {0, _} ->
-      wolff_metrics:queuing_set(Config, 0);
+      wolff_metrics:queuing_set(Config, 0),
+      wolff_metrics:queuing_bytes_set(Config, 0);
     {_, false} ->
-      wolff_metrics:queuing_set(Config, 0);
+      wolff_metrics:queuing_set(Config, 0),
+      wolff_metrics:queuing_bytes_set(Config, 0);
     {_, _} ->
       ok
   end.
@@ -505,6 +508,7 @@ send_to_kafka(#{sent_reqs := SentReqs,
   IDs = lists:map(fun({ID, _}) -> ID end, get_calls_from_queue_items(Items)),
   NewPendingAcks = wolff_pendack:move_backlog_to_inflight(PendingAcks, IDs),
   wolff_metrics:queuing_set(Config, replayq:count(NewQ)),
+  wolff_metrics:queuing_bytes_set(Config, replayq:bytes(NewQ)),
   NewSentReqsCount = SentReqsCount + 1,
   NrOfCalls = count_calls(Items),
   NewInflightCalls = InflightCalls + NrOfCalls,
@@ -923,6 +927,7 @@ enqueue_calls2(Calls,
       end, {[], PendingAcks0, 0}, Calls),
    NewQ = replayq:append(Q, lists:reverse(QueueItems)),
    wolff_metrics:queuing_set(Config0, replayq:count(NewQ)),
+   wolff_metrics:queuing_bytes_set(Config0, replayq:bytes(NewQ)),
    lists:foreach(fun maybe_reply_queued/1, Calls),
    Overflow = case maps:get(drop_if_highmem, Config0, false)
                   andalso replayq:is_mem_only(NewQ)
@@ -968,6 +973,7 @@ handle_overflow(#{replayq := Q,
   wolff_metrics:dropped_queue_full_inc(Config, NrOfCalls),
   wolff_metrics:dropped_inc(Config, NrOfCalls),
   wolff_metrics:queuing_set(Config, replayq:count(NewQ)),
+  wolff_metrics:queuing_bytes_set(Config, replayq:bytes(NewQ)),
   ok = maybe_log_discard(St, NrOfCalls),
   {CbList, NewPendingAcks} = wolff_pendack:drop_backlog(PendingAcks, CallIDs),
   lists:foreach(fun(Cb) -> eval_ack_cb(Cb, ?buffer_overflow_discarded) end, CbList),
diff --git a/test/wolff_supervised_tests.erl b/test/wolff_supervised_tests.erl
index b4f60cb..a6c7d01 100644
--- a/test/wolff_supervised_tests.erl
+++ b/test/wolff_supervised_tests.erl
@@ -31,6 +31,7 @@ supervised_client_test() ->
   ok = application:stop(wolff),
   ?assertEqual(undefined, whereis(wolff_sup)),
   assert_last_event_is_zero(queuing, CntrEventsTable),
+  assert_last_event_is_zero(queuing_bytes, CntrEventsTable),
   assert_last_event_is_zero(inflight, CntrEventsTable),
   [1] = get_telemetry_seq(CntrEventsTable, [wolff,success]),
   ets:delete(CntrEventsTable),
@@ -65,6 +66,7 @@ test_supervised_producers(Name) ->
   ?assertEqual([], supervisor:which_children(wolff_client_sup)),
   ok = application:stop(wolff),
   assert_last_event_is_zero(queuing, CntrEventsTable),
+  assert_last_event_is_zero(queuing_bytes, CntrEventsTable),
   assert_last_event_is_zero(inflight, CntrEventsTable),
   [1] = get_telemetry_seq(CntrEventsTable, [wolff,success]),
   ets:delete(CntrEventsTable),
@@ -175,6 +177,7 @@ test_client_restart(ClientId, Topic, Partition) ->
   ok = application:stop(wolff),
   [1,1] = get_telemetry_seq(CntrEventsTable, [wolff,success]),
   assert_last_event_is_zero(queuing, CntrEventsTable),
+  assert_last_event_is_zero(queuing_bytes, CntrEventsTable),
   assert_last_event_is_zero(inflight, CntrEventsTable),
   ets:delete(CntrEventsTable),
   wolff_tests:deinstall_event_logging(?FUNCTION_NAME),
@@ -256,6 +259,7 @@ producer_restart_test() ->
   ok = application:stop(wolff),
   [1,2] = get_telemetry_seq(CntrEventsTable, [wolff,success]),
   assert_last_event_is_zero(queuing, CntrEventsTable),
+  assert_last_event_is_zero(queuing_bytes, CntrEventsTable),
   assert_last_event_is_zero(inflight, CntrEventsTable),
   ets:delete(CntrEventsTable),
   wolff_tests:deinstall_event_logging(?FUNCTION_NAME),
@@ -322,6 +326,7 @@ test_partition_count_refresh() ->
   ?assertEqual(Partitions0, Partition1),
   [1,1] = get_telemetry_seq(CntrEventsTable, [wolff,success]),
   assert_last_event_is_zero(queuing, CntrEventsTable),
+  assert_last_event_is_zero(queuing_bytes, CntrEventsTable),
   assert_last_event_is_zero(inflight, CntrEventsTable),
   ets:delete(CntrEventsTable),
   wolff_tests:deinstall_event_logging(?FUNCTION_NAME),
diff --git a/test/wolff_tests.erl b/test/wolff_tests.erl
index e65e538..b91ac3b 100644
--- a/test/wolff_tests.erl
+++ b/test/wolff_tests.erl
@@ -117,6 +117,10 @@ send_test() ->
   ?assert_eq_optional_tail(
      wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, queuing])),
      [0,1,0]),
+  ?assertMatch(
+     [0,N,0] when N > 0,
+     wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, queuing_bytes]))
+    ),
   ?assert_eq_optional_tail(
      wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, inflight])),
      [0,1,0]),
@@ -155,6 +159,9 @@ send_one_msg_max_batch_test() ->
   ?assert_eq_optional_tail(
      wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, queuing])),
      [0,1,0]),
+  ?assert_eq_optional_tail(
+     wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, queuing_bytes])),
+     [0,EstimatedBytes,0]),
   ?assert_eq_optional_tail(
      wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, inflight])),
      [0,1,0]),
@@ -192,6 +199,9 @@ send_smallest_msg_max_batch_test() ->
   ?assert_eq_optional_tail(
      wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, queuing])),
      [0,1,0]),
+  ?assert_eq_optional_tail(
+     wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, queuing_bytes])),
+     [0,batch_bytes(Batch),0]),
   ?assert_eq_optional_tail(
      wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, inflight])),
      [0,1,0]),
@@ -432,6 +442,9 @@ replayq_overflow_test() ->
   ?assert_eq_optional_tail(
      wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, queuing])),
      [0,2,1,0]),
+  ?assert_eq_optional_tail(
+     wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, queuing_bytes])),
+     [0,64,32,0]),
   ?assert_eq_optional_tail(
      wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, inflight])),
      [0,1,0]),
@@ -503,6 +516,9 @@ replayq_highmem_overflow_test() ->
   ?assert_eq_optional_tail(
      wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, queuing])),
      [0, 1, 0, 1, 0, 1, 0]),
+  ?assert_eq_optional_tail(
+     wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, queuing_bytes])),
+     [0,32,0,32,0,32,0]),
   ?assert_eq_optional_tail(
      wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, inflight])),
      [0,1,0]),
@@ -599,6 +615,9 @@ replayq_offload_test() ->
   ?assert_eq_optional_tail(
      wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, queuing])),
      [0, 1, 0]),
+  ?assert_eq_optional_tail(
+     wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, queuing_bytes])),
+     [0, 61, 0]),
   ?assert_eq_optional_tail(
      wolff_test_utils:dedup_list(get_telemetry_seq(CntrEventsTable, [wolff, inflight])),
      [0, 1, 0]),
@@ -1001,6 +1020,7 @@ telemetry_events() ->
       [wolff, dropped_queue_full],
       [wolff, matched],
       [wolff, queuing],
+      [wolff, queuing_bytes],
       [wolff, retried],
       [wolff, failed],
       [wolff, inflight],