diff --git a/quickemu b/quickemu
index 43d4c7b..cddc36f 100755
--- a/quickemu
+++ b/quickemu
@@ -297,22 +297,27 @@ function vm_boot() {
       RAM_HOST=$(free --mega -h | grep Mem | cut -d':' -f2 | cut -d'G' -f1 | sed 's/ //g')
       #Round up - https://github.com/wimpysworld/quickemu/issues/11
       RAM_HOST=$(printf '%.*f\n' 0 "${RAM_HOST}")
-      if [ "${RAM_HOST}" -ge 256 ]; then
+      if [ "${RAM_HOST}" -ge 128 ]; then
         RAM_VM="32G"
-      elif [ "${RAM_HOST}" -ge 128 ]; then
-        RAM_VM="16G"
       elif [ "${RAM_HOST}" -ge 64 ]; then
-        RAM_VM="8G"
-      elif [ "${RAM_HOST}" -ge 32 ]; then
-        RAM_VM="4G"
+        RAM_VM="16G"
       elif [ "${RAM_HOST}" -ge 16 ]; then
-        RAM_VM="3G"
+        RAM_VM="8G"
+      elif [ "${RAM_HOST}" -ge 8 ]; then
+        RAM_VM="4G"
       fi
   else
       RAM_VM="${ram}"
   fi
   echo ", ${RAM_VM} RAM"
 
+  if [ ${RAM_VM//G/} -lt 4 ]; then
+    if [ "${guest_os}" == "macos" ] || [ "${guest_os}" == "windows" ]; then
+        echo "ERROR! You have insufficient RAM to run ${guest_os} in a VM"
+        exit 1
+    fi
+  fi
+
   # Make any OS specific adjustments
   case ${guest_os} in
     freebsd|linux)