diff --git a/main.h b/main.h
index c5a0127..c92592a 100644
--- a/main.h
+++ b/main.h
@@ -14,7 +14,10 @@ class CBlockIndex;
 class CWalletTx;
 class CKeyItem;
 
-static const unsigned int MAX_BLOCK_SIZE = 1000000;
+static const unsigned int TX_PER_MINUTE = 1400;
+static const unsigned int TX_AVG_SIZE_GUESS = 256;
+static const unsigned int MAX_BLOCK_SIZE =
+ TX_PER_MINUTE * TX_AVG_SIZE_GUESS * 10 * 2;
 static const unsigned int MAX_BLOCK_SIZE_GEN = MAX_BLOCK_SIZE/2;
 static const int MAX_BLOCK_SIGOPS = MAX_BLOCK_SIZE/50;
 static const int64 COIN = 100000000;