diff --git a/include/libtorrent/stat.hpp b/include/libtorrent/stat.hpp
index 84daec3af..64ef64af0 100755
--- a/include/libtorrent/stat.hpp
+++ b/include/libtorrent/stat.hpp
@@ -143,16 +143,21 @@ namespace libtorrent
 		// calculate ip protocol overhead
 		void calc_ip_overhead()
 		{
-			// traffic balance is the number of bytes we downloaded
-			// more than we uploaded
-			int traffic_balance = m_stat[download_protocol].counter()
-				+ m_stat[download_payload].counter()
-				- m_stat[upload_protocol].counter()
-				- m_stat[upload_payload].counter();
-			if (traffic_balance > 0)
-				m_stat[upload_ip_protocol].add(traffic_balance / 20);
-			else
-				m_stat[download_ip_protocol].add(-traffic_balance / 20);
+			int uploaded = m_stat[upload_protocol].counter()
+				+ m_stat[upload_payload].counter();
+			int downloaded = m_stat[download_protocol].counter()
+				+ m_stat[download_payload].counter();
+
+			// IP + TCP headers are 40 bytes per MTU (1460)
+			// bytes of payload, but at least 40 bytes
+			m_stat[upload_ip_protocol].add((std::max)(uploaded / 1460, 40));
+			m_stat[download_ip_protocol].add((std::max)(downloaded / 1460, 40));
+
+			// also account for ACK traffic. That adds to the transfers
+			// in the opposite direction. Even on connections with symmetric
+			// transfer rates, it seems to add a penalty.
+			m_stat[upload_ip_protocol].add((std::max)(downloaded / 20, 40));
+			m_stat[download_ip_protocol].add((std::max)(uploaded / 20, 40));
 		}
 
 		int upload_ip_overhead() const { return m_stat[upload_ip_protocol].counter(); }