diff --git a/esphome/components/api/api_connection.cpp b/esphome/components/api/api_connection.cpp
index f12141e197a..4e0663d7f48 100644
--- a/esphome/components/api/api_connection.cpp
+++ b/esphome/components/api/api_connection.cpp
@@ -2033,8 +2033,7 @@ uint16_t APIConnection::encode_to_buffer(uint32_t calculated_size, MessageEncode
     // Batch message second or later
     // Reserve for full message, resize to include footer gap + header padding + payload
     size_t current_size = shared_buf.size();
-    shared_buf.reserve_and_resize(current_size + total_calculated_size,
-                                  current_size + footer_size + header_padding + calculated_size);
+    shared_buf.resize(current_size + total_calculated_size);
     write_start = shared_buf.size() - calculated_size;
   }
 
@@ -2042,7 +2041,7 @@ uint16_t APIConnection::encode_to_buffer(uint32_t calculated_size, MessageEncode
   encode_fn(msg, buffer);
 
   // Return total size (header + payload + footer)
-  return static_cast<uint16_t>(header_padding + calculated_size + footer_size);
+  return static_cast<uint16_t>(total_calculated_size);
 }
 bool APIConnection::send_buffer(ProtoWriteBuffer buffer, uint8_t message_type) {
   const bool is_log_message = (message_type == SubscribeLogsResponse::MESSAGE_TYPE);