diff --git a/src/aggregator/client/m3msg_client.go b/src/aggregator/client/m3msg_client.go
index b4d297cd86..26ef7e1217 100644
--- a/src/aggregator/client/m3msg_client.go
+++ b/src/aggregator/client/m3msg_client.go
@@ -111,7 +111,8 @@ func (c *M3MsgClient) WriteUntimedCounter(
 			metadatas: metadatas,
 		},
 	}
-	err := c.write(counter.ID, payload)
+	size, err := c.write(counter.ID, payload)
+	c.metrics.totalBytesSent.Inc(int64(size))
 	c.metrics.writeUntimedCounter.ReportSuccessOrError(err, c.nowFn().Sub(callStart))
 	return err
 }
@@ -129,7 +130,8 @@ func (c *M3MsgClient) WriteUntimedBatchTimer(
 			metadatas: metadatas,
 		},
 	}
-	err := c.write(batchTimer.ID, payload)
+	size, err := c.write(batchTimer.ID, payload)
+	c.metrics.totalBytesSent.Inc(int64(size))
 	c.metrics.writeUntimedBatchTimer.ReportSuccessOrError(err, c.nowFn().Sub(callStart))
 	return err
 }
@@ -147,7 +149,8 @@ func (c *M3MsgClient) WriteUntimedGauge(
 			metadatas: metadatas,
 		},
 	}
-	err := c.write(gauge.ID, payload)
+	size, err := c.write(gauge.ID, payload)
+	c.metrics.totalBytesSent.Inc(int64(size))
 	c.metrics.writeUntimedGauge.ReportSuccessOrError(err, c.nowFn().Sub(callStart))
 	return err
 }
@@ -165,7 +168,8 @@ func (c *M3MsgClient) WriteTimed(
 			metadata: metadata,
 		},
 	}
-	err := c.write(metric.ID, payload)
+	size, err := c.write(metric.ID, payload)
+	c.metrics.totalBytesSent.Inc(int64(size))
 	c.metrics.writeForwarded.ReportSuccessOrError(err, c.nowFn().Sub(callStart))
 	return err
 }
@@ -183,7 +187,8 @@ func (c *M3MsgClient) WritePassthrough(
 			storagePolicy: storagePolicy,
 		},
 	}
-	err := c.write(metric.ID, payload)
+	size, err := c.write(metric.ID, payload)
+	c.metrics.totalBytesSent.Inc(int64(size))
 	c.metrics.writePassthrough.ReportSuccessOrError(err, c.nowFn().Sub(callStart))
 	return err
 }
@@ -201,7 +206,8 @@ func (c *M3MsgClient) WriteTimedWithStagedMetadatas(
 			metadatas: metadatas,
 		},
 	}
-	err := c.write(metric.ID, payload)
+	size, err := c.write(metric.ID, payload)
+	c.metrics.totalBytesSent.Inc(int64(size))
 	c.metrics.writeForwarded.ReportSuccessOrError(err, c.nowFn().Sub(callStart))
 	return err
 }
@@ -219,27 +225,29 @@ func (c *M3MsgClient) WriteForwarded(
 			metadata: metadata,
 		},
 	}
-	err := c.write(metric.ID, payload)
+	size, err := c.write(metric.ID, payload)
+	c.metrics.totalBytesSent.Inc(int64(size))
 	c.metrics.writeForwarded.ReportSuccessOrError(err, c.nowFn().Sub(callStart))
 	return err
 }
 
 //nolint:gocritic
-func (c *M3MsgClient) write(metricID id.RawID, payload payloadUnion) error {
+func (c *M3MsgClient) write(metricID id.RawID, payload payloadUnion) (int, error) {
 	shard := c.shardFn(metricID, c.m3msg.numShards)
 
 	msg := c.m3msg.messagePool.Get()
-	if err := msg.Encode(shard, payload); err != nil {
+	size, err := msg.Encode(shard, payload)
+	if err != nil {
 		msg.Finalize(producer.Dropped)
-		return err
+		return 0, err
 	}
 
 	if err := c.m3msg.producer.Produce(msg); err != nil {
 		msg.Finalize(producer.Dropped)
-		return err
+		return 0, err
 	}
 
-	return nil
+	return size, nil
 }
 
 // Flush satisfies Client interface, as M3Msg client does not need explicit flushing.
@@ -259,6 +267,7 @@ type m3msgClientMetrics struct {
 	writeUntimedGauge      instrument.MethodMetrics
 	writePassthrough       instrument.MethodMetrics
 	writeForwarded         instrument.MethodMetrics
+	totalBytesSent         tally.Counter
 }
 
 func newM3msgClientMetrics(
@@ -271,6 +280,7 @@ func newM3msgClientMetrics(
 		writeUntimedGauge:      instrument.NewMethodMetrics(scope, "writeUntimedGauge", opts),
 		writePassthrough:       instrument.NewMethodMetrics(scope, "writePassthrough", opts),
 		writeForwarded:         instrument.NewMethodMetrics(scope, "writeForwarded", opts),
+		totalBytesSent:         scope.Counter("total-bytes-sent"),
 	}
 }
 
@@ -324,7 +334,7 @@ func newMessage(pool *messagePool) *message {
 func (m *message) Encode(
 	shard uint32,
 	payload payloadUnion,
-) error {
+) (int, error) {
 	m.shard = shard
 
 	switch payload.payloadType {
@@ -336,7 +346,7 @@ func (m *message) Encode(
 				StagedMetadatas: payload.untimed.metadatas,
 			}
 			if err := value.ToProto(&m.cm); err != nil {
-				return err
+				return 0, err
 			}
 
 			m.metric = metricpb.MetricWithMetadatas{
@@ -349,7 +359,7 @@ func (m *message) Encode(
 				StagedMetadatas: payload.untimed.metadatas,
 			}
 			if err := value.ToProto(&m.bm); err != nil {
-				return err
+				return 0, err
 			}
 
 			m.metric = metricpb.MetricWithMetadatas{
@@ -362,7 +372,7 @@ func (m *message) Encode(
 				StagedMetadatas: payload.untimed.metadatas,
 			}
 			if err := value.ToProto(&m.gm); err != nil {
-				return err
+				return 0, err
 			}
 
 			m.metric = metricpb.MetricWithMetadatas{
@@ -370,7 +380,7 @@ func (m *message) Encode(
 				GaugeWithMetadatas: &m.gm,
 			}
 		default:
-			return fmt.Errorf("unrecognized metric type: %v",
+			return 0, fmt.Errorf("unrecognized metric type: %v",
 				payload.untimed.metric.Type)
 		}
 	case forwardedType:
@@ -379,7 +389,7 @@ func (m *message) Encode(
 			ForwardMetadata: payload.forwarded.metadata,
 		}
 		if err := value.ToProto(&m.fm); err != nil {
-			return err
+			return 0, err
 		}
 
 		m.metric = metricpb.MetricWithMetadatas{
@@ -392,7 +402,7 @@ func (m *message) Encode(
 			TimedMetadata: payload.timed.metadata,
 		}
 		if err := value.ToProto(&m.tm); err != nil {
-			return err
+			return 0, err
 		}
 
 		m.metric = metricpb.MetricWithMetadatas{
@@ -405,7 +415,7 @@ func (m *message) Encode(
 			StagedMetadatas: payload.timedWithStagedMetadatas.metadatas,
 		}
 		if err := value.ToProto(&m.tms); err != nil {
-			return err
+			return 0, err
 		}
 
 		m.metric = metricpb.MetricWithMetadatas{
@@ -413,7 +423,7 @@ func (m *message) Encode(
 			TimedMetricWithMetadatas: &m.tms,
 		}
 	default:
-		return fmt.Errorf("unrecognized payload type: %v",
+		return 0, fmt.Errorf("unrecognized payload type: %v",
 			payload.payloadType)
 	}
 
@@ -427,7 +437,7 @@ func (m *message) Encode(
 	m.buf = m.buf[:size]
 
 	_, err := m.metric.MarshalTo(m.buf)
-	return err
+	return size, err
 }
 
 func (m *message) Shard() uint32 {
diff --git a/src/aggregator/client/m3msg_client_test.go b/src/aggregator/client/m3msg_client_test.go
index 9c76c8e84f..2f78295c22 100644
--- a/src/aggregator/client/m3msg_client_test.go
+++ b/src/aggregator/client/m3msg_client_test.go
@@ -22,11 +22,17 @@ package client
 
 import (
 	"testing"
+	"time"
 
 	"github.com/golang/mock/gomock"
 	"github.com/stretchr/testify/assert"
+	"github.com/uber-go/tally"
 
+	"github.com/m3db/m3/src/metrics/metadata"
+	"github.com/m3db/m3/src/metrics/metric/id"
+	"github.com/m3db/m3/src/metrics/metric/unaggregated"
 	"github.com/m3db/m3/src/msg/producer"
+	"github.com/m3db/m3/src/x/instrument"
 )
 
 func TestNewM3MsgClient(t *testing.T) {
@@ -42,3 +48,43 @@ func TestNewM3MsgClient(t *testing.T) {
 	assert.NotNil(t, c)
 	assert.NoError(t, err)
 }
+
+func TestTotalBytesAdded(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	// Mock dependencies
+	p := producer.NewMockProducer(ctrl)
+	p.EXPECT().Init()
+	p.EXPECT().NumShards().Return(uint32(1))
+	p.EXPECT().Produce(gomock.Any()).Return(nil).AnyTimes()
+
+	opts := NewM3MsgOptions().SetProducer(p)
+	client, err := NewM3MsgClient(NewOptions().SetM3MsgOptions(opts))
+	assert.NoError(t, err)
+
+	// Mock metric and metadata
+	counter := unaggregated.Counter{
+		ID:    id.RawID("testCounter"),
+		Value: 123,
+	}
+	metadatas := metadata.StagedMetadatas{}
+
+	// Mock time function
+	now := time.Now()
+	client.(*M3MsgClient).nowFn = func() time.Time { return now }
+
+	testScope := tally.NewTestScope("", make(map[string]string))
+	// Mock metrics
+	client.(*M3MsgClient).metrics = m3msgClientMetrics{
+		writeUntimedCounter: instrument.NewMethodMetrics(testScope, "writeUntimedCounter", instrument.TimerOptions{}),
+		totalBytesSent:      testScope.Counter("total-bytes-sent"),
+	}
+
+	// Call the method
+	err = client.WriteUntimedCounter(counter, metadatas)
+	assert.NoError(t, err)
+
+	// Verify the total bytes added
+	assert.Equal(t, int64(23), testScope.Snapshot().Counters()["total-bytes-sent+"].Value())
+}