diff --git a/include/bluetooth/l2cap.h b/include/bluetooth/l2cap.h
index b02bae68eca..7ba11f359fa 100644
--- a/include/bluetooth/l2cap.h
+++ b/include/bluetooth/l2cap.h
@@ -38,11 +38,6 @@
 #include <net/buf.h>
 #include <bluetooth/conn.h>
 
-/* Helper to calculate needed outgoing buffer size */
-#define BT_L2CAP_BUF_SIZE(mtu) (CONFIG_BLUETOOTH_HCI_SEND_RESERVE + \
-				sizeof(struct bt_hci_acl_hdr) + \
-				sizeof(struct bt_l2cap_hdr) + (mtu))
-
 /** @brief L2CAP Endpoint structure. */
 struct bt_l2cap_endpoint {
 	/** Endpoint CID */
diff --git a/net/bluetooth/l2cap_internal.h b/net/bluetooth/l2cap_internal.h
index b6eae76a1d5..b8b6a2f0c96 100644
--- a/net/bluetooth/l2cap_internal.h
+++ b/net/bluetooth/l2cap_internal.h
@@ -107,6 +107,11 @@ struct bt_l2cap_le_credits {
 	uint16_t credits;
 } __packed;
 
+/* Helper to calculate needed outgoing buffer size */
+#define BT_L2CAP_BUF_SIZE(mtu) (CONFIG_BLUETOOTH_HCI_SEND_RESERVE + \
+				sizeof(struct bt_hci_acl_hdr) + \
+				sizeof(struct bt_l2cap_hdr) + (mtu))
+
 struct bt_l2cap_fixed_chan {
 	uint16_t		cid;