diff --git a/DRAMSys/simulator/src/simulation/Dram.h b/DRAMSys/simulator/src/simulation/Dram.h
index 7db71f78..85dfdf8a 100644
--- a/DRAMSys/simulator/src/simulation/Dram.h
+++ b/DRAMSys/simulator/src/simulation/Dram.h
@@ -94,8 +94,11 @@ struct Dram : sc_module
 
     SC_CTOR(Dram) : tSocket("socket")
     {
-        // FIXME: memory size
-        unsigned int size = 1024 * 1024 * 1024;
+        // calculate memory size
+        unsigned int banks = Configuration::getInstance().memSpec.NumberOfBanks;
+        unsigned int rows = Configuration::getInstance().memSpec.NumberOfRows;
+        unsigned int columns = Configuration::getInstance().memSpec.NumberOfColumns;
+        unsigned int size = banks * rows * columns;
         memory = (unsigned char *)mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON | MAP_NORESERVE, -1, 0);
 
         tSocket.register_nb_transport_fw(this, &Dram::nb_transport_fw);