diff --git a/bramble-api/src/main/java/org/briarproject/bramble/api/sync/event/MessagesSentEvent.java b/bramble-api/src/main/java/org/briarproject/bramble/api/sync/event/MessagesSentEvent.java
index 1f392417d..179907a3a 100644
--- a/bramble-api/src/main/java/org/briarproject/bramble/api/sync/event/MessagesSentEvent.java
+++ b/bramble-api/src/main/java/org/briarproject/bramble/api/sync/event/MessagesSentEvent.java
@@ -18,11 +18,13 @@ public class MessagesSentEvent extends Event {
 
 	private final ContactId contactId;
 	private final Collection<MessageId> messageIds;
+	private final long totalLength;
 
 	public MessagesSentEvent(ContactId contactId,
-			Collection<MessageId> messageIds) {
+			Collection<MessageId> messageIds, long totalLength) {
 		this.contactId = contactId;
 		this.messageIds = messageIds;
+		this.totalLength = totalLength;
 	}
 
 	public ContactId getContactId() {
@@ -32,4 +34,8 @@ public class MessagesSentEvent extends Event {
 	public Collection<MessageId> getMessageIds() {
 		return messageIds;
 	}
+
+	public long getTotalLength() {
+		return totalLength;
+	}
 }
diff --git a/bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseComponentImpl.java b/bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseComponentImpl.java
index 3bb052fe9..f3e818644 100644
--- a/bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseComponentImpl.java
+++ b/bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseComponentImpl.java
@@ -415,14 +415,17 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 			throw new NoSuchContactException();
 		Collection<MessageId> ids =
 				db.getMessagesToSend(txn, c, maxLength, maxLatency);
+		long totalLength = 0;
 		List<Message> messages = new ArrayList<>(ids.size());
 		for (MessageId m : ids) {
-			messages.add(db.getMessage(txn, m));
+			Message message = db.getMessage(txn, m);
+			totalLength += message.getRawLength();
+			messages.add(message);
 			db.updateExpiryTimeAndEta(txn, c, m, maxLatency);
 		}
 		if (ids.isEmpty()) return null;
 		db.lowerRequestedFlag(txn, c, ids);
-		transaction.attach(new MessagesSentEvent(c, ids));
+		transaction.attach(new MessagesSentEvent(c, ids, totalLength));
 		return messages;
 	}
 
@@ -467,14 +470,17 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 			throw new NoSuchContactException();
 		Collection<MessageId> ids =
 				db.getRequestedMessagesToSend(txn, c, maxLength, maxLatency);
+		long totalLength = 0;
 		List<Message> messages = new ArrayList<>(ids.size());
 		for (MessageId m : ids) {
-			messages.add(db.getMessage(txn, m));
+			Message message = db.getMessage(txn, m);
+			totalLength += message.getRawLength();
+			messages.add(message);
 			db.updateExpiryTimeAndEta(txn, c, m, maxLatency);
 		}
 		if (ids.isEmpty()) return null;
 		db.lowerRequestedFlag(txn, c, ids);
-		transaction.attach(new MessagesSentEvent(c, ids));
+		transaction.attach(new MessagesSentEvent(c, ids, totalLength));
 		return messages;
 	}
 
diff --git a/briar-headless/src/test/java/org/briarproject/briar/headless/messaging/MessagingControllerImplTest.kt b/briar-headless/src/test/java/org/briarproject/briar/headless/messaging/MessagingControllerImplTest.kt
index fe0120322..588caf0db 100644
--- a/briar-headless/src/test/java/org/briarproject/briar/headless/messaging/MessagingControllerImplTest.kt
+++ b/briar-headless/src/test/java/org/briarproject/briar/headless/messaging/MessagingControllerImplTest.kt
@@ -136,7 +136,7 @@ internal class MessagingControllerImplTest : ControllerTest() {
         val messageId1 = MessageId(getRandomId())
         val messageId2 = MessageId(getRandomId())
         val messageIds = listOf(messageId1, messageId2)
-        val event = MessagesSentEvent(contact.id, messageIds)
+        val event = MessagesSentEvent(contact.id, messageIds, 1234)
 
         every {
             webSocketController.sendEvent(
@@ -274,7 +274,7 @@ internal class MessagingControllerImplTest : ControllerTest() {
         val messageId1 = MessageId(getRandomId())
         val messageId2 = MessageId(getRandomId())
         val messageIds = listOf(messageId1, messageId2)
-        val event = MessagesSentEvent(contact.id, messageIds)
+        val event = MessagesSentEvent(contact.id, messageIds, 1234)
 
         val json = """
             {