diff --git a/esphome/components/mqtt/mqtt_component.cpp b/esphome/components/mqtt/mqtt_component.cpp
index 66f6a1e6255..70b9936c894 100644
--- a/esphome/components/mqtt/mqtt_component.cpp
+++ b/esphome/components/mqtt/mqtt_component.cpp
@@ -232,7 +232,7 @@ bool MQTTComponent::send_discovery_() {
 #else
         const char *fmt = ver_fmt;
 #endif
-        // sizeof(ver_fmt) + 8: format specifier expands to 8 hex digits, plus safety margin
+        // Buffer sized for format string expansion: ~4 bytes net growth from format specifier to 8 hex digits, plus safety margin
         char version_buf[sizeof(ver_fmt) + 8];
         snprintf(version_buf, sizeof(version_buf), fmt, App.get_config_hash());
         device_info[MQTT_DEVICE_SW_VERSION] = version_buf;